Wheat Production Guides.pdf - Pannar Seed

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Wheat Production Guides.pdf - Pannar Seed

PANNAR SEED (PTY) LTD

Production Guide Series

Wheat

TABLE OF CONTENTS

A) INTRODUCTION ............................................................................................................. 1

B) CULTIVAR INFORMATION – FIRST STEP TO SUCCESSFUL

WHEAT PRODUCTION .................................................................................................. 2

1. Introduction ......................................................................................................... 2

2. Plant Breeders’ Rights ........................................................................................ 2

3. Certified seed is the key to success ................................................................... 2

4. Cultivar selection ................................................................................................. 2

C) SOIL PREPARATION ................................................................................................... .8

1. Conventional tillage seedbed preparation ........................................................ .8

2. Conservation tillage seeding systems ............................................................... 9

D) YIELD PLANNING ......................................................................................................... 9

E) FERTILISING GUIDELINES FOR WHEAT PRODUCTION ....................................... 10

1. Soil acidity ...................................................................................................... 11

2. Nitrogen fertilisation ........................................................................................ 12

3. Phosphate fertilisation .................................................................................... 16

4. Potassium fertilisation .................................................................................... 18

5. Micro-elements ............................................................................................... 19

F) WATER QUALITY AND WEED HERBICIDES ........................................................... 20

1. Factors that affect the salt antagonism of herbicides .................................... 20

G) INSECT CONTROL ...................................................................................................... 21

1. Aphids ............................................................................................................. 22

2. Other insect pests ........................................................................................... 24

H) DISEASE CONTROL .................................................................................................. 26

1. The risk of fungal infection ............................................................................. 26

2. Chemical control of fungal diseases .............................................................. 26

3. Root diseases ................................................................................................. 28

4. Stem, leaf and spike diseases ....................................................................... 29

5. Smut ................................................................................................................ 33

I) GRADING AND QUALITY ............................................................................................ 34

J) BIBLIOGRAPHY ........................................................................................................... 35


A) INTRODUCTION

In South Africa, wheat is produced in both the summer and winter rainfall regions.

Approximately 50% of the total area planted to wheat locally is cultivated under

dryland conditions in the summer rainfall region. Although production under irrigation

in the summer rainfall region amounts to less than 15% of the total area cultivated

locally, as much as 30% of the total wheat harvest is produced under irrigation due to

the higher yield potential.

Dryland wheat production in South Africa is distinctive for its low average yield in

comparison with most of the major wheat producing countries. The stringent quality

requirements for newly released cultivars are often blamed for slower than expected

progress in yield increases of local breeding programmes. Other limiting factors such

as variable climate conditions (including dry, warm winters) and low soil fertility,

however also have an effect. Yield losses were also caused by the introduction of

new diseases such as yellow/stripe rust (Puccinia striiformis) in 1996 and the

subsequent emergence of new pathotypes, as well as the introduction of the Russian

wheat aphid in 1978 and the emergence of a new biotype in 2005. The indirect

consequence thereof was that breeding programmes discontinued many promising

germplasm lines with higher yield potentials due to susceptibility to new diseases such

as yellow/stripe rust or more virulent disease-causing organisms or pests. This

resulted in local breeding programmes making more progress in creating specific

resistance or quality characteristics as opposed to improving yield performance. Farm

saved seed as well as the illegal sale of wheat seed has reduced the profitability of

wheat breeding programmes and if these practices continue unabated the profitability

of future wheat production will be significantly reduced, as the development of new,

improved cultivars will lag behind.

Notwithstanding these considerations, the local wheat producer must be able to grow

wheat profitably and stand in direct competition with imported wheat. To increase

profits per area unit, producers continuously improve their planning and seek more

information regarding best management practices. This guide is aimed at helping the

producer make more informed decisions for profitable wheat production.

Figure 1: Botanical Diagram of Wheat Plant

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B) CULTIVAR INFORMATION – FIRST STEP TO SUCCESSFUL WHEAT

PRODUCTION

1. INTRODUCTION

Cultivar selection is one of the most important considerations in risk management and

maximising yields. Cultivars differ in characteristics such as area adaptability, yield

potential and stability, agronomic characteristics and in terms of tolerance to

diseases, pests and aluminium toxicity. Although there is no perfect cultivar, the

producer can put together a package to minimise or neutralise the riskiest aspects of

wheat production in the specific area or farm.

2. PLANT BREEDERS’ RIGHTS

The aim of this Act (Act No. 15 of 1976) is to protect companies that invest millions of

Rands in cultivar development and provide legal protection to cultivar breeders and

owners. The rights of the cultivar breeder or owner include that no party may multiply,

prepare for planting, sell, export or keep seed in stock without the necessary

authorisation or licence from the holders of the rights. Upon conviction, the guilty

party shall be liable to a fine or imprisonment. There are several examples of

successful persecutions under this law.

3. CERTIFIED SEED IS THE KEY TO SUCCESS

The primary objective of seed certification is the maintenance of genetic purity in

seed. All requirements and standards of certified seed production are prescribed by

seed laws and regulations. The ultimate objective is to create seed with high genetic

purity, which is binding for cultivars listed on “Table 8”. Cultivar authenticity and seed

quality is therefore guaranteed. This offers a buyer protection and peace of mind as

well as a system for the follow up of complaints and possible claims.

4. CULTIVAR SELECTION

The selection of a cultivar is principally an economic decision, where the producer

must find a balance between risk and yield potential. Cultivar selection should be

based on reliable long-term data and should be revised annually to make provision for

new, improved cultivars. This should ensure the highest average profit per production

unit in the long term. A summary of the important considerations in cultivar selection is

provided below. The PANNAR product catalogue provides a comprehensive

summary of the most up-to-date information available on the PANNAR range of wheat

cultivars. This information is based on perennial research results and is given in good

faith. Producers must be aware that the development of new rust pathotypes and new

Russian wheat aphid biotypes may influence cultivar reactions within a given season.

The product catalogue is updated annually to ensure that the most recent information

is available to producers.


Yield potential:

Wheat cultivars differ in terms of yield potential; certain cultivars only perform at low

yield potential levels, while others are only adapted for high yield potential levels.

Where spring rainfall is the yield-determining factor, the ideal cultivar is the one that

produces competitive results under both high and low yield potential levels. In

general, the long growing season cultivars are less suited to areas with a low yield

potential, either due to shallow soils or long-term climate conditions. The selection of

cultivars should therefore be based on the long-term yield potential of a specific land

area or farm where soil, climate and manageability should be the determining factors.

Plant disease and pests:

The prevalence of a specific disease or pest in the area should be the determining

factor here. In areas of high disease or pest prevalence, the producer should

consider a more tolerant or resistant cultivar. This affords the producer the opportunity

to manage input costs over the long term and reduce the risk of crop damage and the

associated yield losses that may result from poor timing of spray applications. The

ability of disease-causing organisms and pests to adapt and therefore to overcome

the resistance must also be kept in mind. Wheat cultivars classified as resistant must,

as with susceptible cultivars, be monitored for the occurrence of diseases or pests

and susceptible reactions on resistant cultivars should be reported to the owner of the

cultivar concerned.

Seed price:

The price of seed is often an important factor when producers exercise their choice of

cultivar(s). More important is the use of independent long-term yield and grading data

when considering whether a more costly wheat cultivar is worthwhile growing in the

particular area.

Agronomic traits:

Agronomic traits such as straw strength and standability are of the utmost importance.

The selection of an unsuitable cultivar or the application of incorrect management

practices may result in significant yield losses. Under irrigation, chemical agents

which work against lodging are used with success on cultivars with a high yield

potential and an inclination to lodge.

An important factor in cultivar selection is aluminium tolerance, especially where the

topsoils and/or sub-soils reach AI 3+ levels that are toxic to sensitive cultivars.

PANNAR offers a range of wheat cultivars for dryland cultivation with strong

aluminium tolerance. This offers producers a short-term solution when lime cannot be

administered on time.

Shattering refers to the measure of how well the ripe kernel is attached to the spike,

as well as to what extent the husks covers and protects the kernel. Under both

irrigation and dryland conditions certain cultivars are more susceptible to bird damage

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and losses during harvesting. These cultivars must be considered with caution in

areas where birds are a potential threat.

Preharvest sprouting tolerance refers to the tolerance a cultivar has against

germination in the spike prior to harvesting. Under normal circumstances newly

released cultivars should not sprout in the spike. Spring types are more prone to

preharvest sprouting than winter types and some cultivars may also be more inclined

to do so than others under conditions of incessant rain during harvesting time.

Grading:

The grading of bread wheat is determined by hectolitre mass, protein content and

falling number. Environmental conditions such as heat and moisture stress during

grain filling and incessant rainfall during harvesting may affect the grade of the grain.

Management practices such moisture conservation and fertilisation may also make

significant contributions to the grade achieved. Although with the release of new

cultivars little deviation from the biological standard of grading characteristics is

allowed, there are genetic differences between cultivars for which the producer must

be prepared. Price differences between the various grades of wheat may negatively

affect the producer’s income per production unit if the cultivar does not compensate

with a higher yield.

Millers’ list:

The National Millers’ Chamber distributes its preference list on an annual basis. The

list must be taken into account during cultivar selection. All wheat cultivars marketed

by PANNAR appear on the millers’ preference list.

5. WHEAT CULTIVAR RECOMMENDATIONS

The selection of a suitable planting date is one of the aspects within the farmer’s

control. Unfortunately, the optimum planting date may vary over seasons due to the

complex interaction between the environment, soil and the plant. One of the most

important determining factors with regards to the optimum planting date is the soil and

air temperature. Good wheat germination will occur at a soil temperature of 4°C to

25°C. The maximum temperature for seedling development is 34°C while the

minimum is approximately -2°C. Thus, wheat is widely adaptable where seedling

development is concerned, which makes for a wide choice of planting dates.

The minimum temperature for leaf, stem and root development is 5°C while the

maximum temperature is 43°C with an optimum of 26°C. The temperate

requirements of the wheat plant during the spike development, pollination and grain

filling stages has a significant bearing on the choice of a suitable planting date as

temperatures outside the physiological limits at these stages may significantly affect

yields. Spike-elongation increases linearly when the air temperature increases from

10°C to 30°C. The optimum temperature for pollination is between 10°C and 25°C

with a minimum of 10°C and a maximum of 32°C. Temperatures outside these limits

result in yield losses due to pollen sterility and the deformation of the pistil and

stamens.


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In the summer rainfall region temperatures rise drastically during September and

October. During this period temperatures may rise higher than the physiological

tolerance limit of the wheat plant with associated yield loss. At the other end of the

spectrum, the reproductive stage is most sensitive to cold stress. When determining

the planting date for a particular cultivar, days to flowering must be taken into

consideration in order to lower the risk of frost occurrence during flowering.

Wheat cultivars are classified as winter, intermediate or spring types according to their

cold requirements. Winter wheat has a high cold requirement (vernalisation) that

must be met before it will produce grain. Spring types on the other hand have no cold

requirement and reach the flowering stage approximately 100 – 114 days after

planting. Wheat remains a cool-weather crop and cool weather conditions in

combination with sufficient moisture is favourable for the determination of yield

potential and optimal spike and grain filling of all wheat types. Winter types (long

growing season) must be planted early to meet their greater cold requirements.

Winter types tiller more readily and can therefore be planted at a lower plant density.

A major challenge for optimal dryland wheat production is the prevention of drought

and cold damage. The planting dates for each production area provided in the

PANNAR catalogue serve as guidelines and are no guarantee against frost and cold

damage. To keep the impact of such damage to a minimum, wheat must not flower

before the cut-off date of high frost risk in the various production areas, regardless of

the planting date.

As new, improved cultivars are released from time to time, it is recommended that the

latest PANNAR brochure or the local PANNAR Representative or Agronomist be

consulted for information regarding the most recent cultivars and recommendations per

production area.


Figure 2: Distribution of the Various Dryland Wheat Production Areas

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Figure 3: Introduction of the Wheat Production Regions under Irrigation

Irrigation areas

Cooler irrigation areas

Warmer irrigation areas

Mpumalanga

Eastern Free State

KwaZulu-Natal

Fish River

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C) SOIL PREPARATION

With the rising fuel prices, soil preparation has become the largest input in

wheat production. This has led producers to consider alternatives such as

chemical weed control to lower their input costs. Unpredictable weather

conditions make it increasingly difficult for wheat producers in the summer

rainfall region to establish a fixed recipe for soil preparation, due to the change

of climatic conditions. For these reasons, it is necessary for producers to plan a

preparation strategy with specific objectives in mind. Some of these objectives

include:

Conservation of groundwater – the most important objective for

successful dryland wheat production

Alleviate soil compactions – necessary for optimal water and root

penetration

Liming – neutralising of acidity

Seedbed preparation – firm seedbed for optimal seedling establishment

Weed control – to minimise moisture loss

Plant disease control – self-sown wheat or grass that may pass on

diseases.

Controlling of wind and water erosion

By striving for specific objectives, producers can try to keep the number of

preparations to a minimum. Soil preparation for small grains is divided into two

basic approaches, namely conventional tillage seedbed preparation and

conservation tillage seeding systems.

1. CONVENTIONAL TILLAGE SEEDBED PREPARATION

The conventional approach is recommended for a wheat-on-wheat

cropping system in which the risk of wind and water erosion is low and

there is a history of root diseases.

Step 1: Harvest December – January.

Step 2: Usually includes a preparation with a disk implement to

cut the rest of the previous harvest finer.

Step 3: Primary preparation with a plough. This preparation

must be carried out in the drier parts between January and the

end of February to ensure that sufficient rain falls on the ploughed

soil and supplements the groundwater. The timing of the

preparation will be determined by the groundwater and the

prospect of rain. The later this preparation can be postponed

due to a possibility of later rains, the fewer preparations are

necessary to control weeds and the less compaction will occur.

Step 4: The preparation is aimed at sealing the soil. It is carried

out by means of a harrow or a sweep cultivator.

Step 5: When necessary, weeds must be controlled with sweep

cultivator preparations. These preparations also serve as

seedbed preparation.

Step 6: Plant according to the guidelines. Where possible, use a

tined planter for the following reasons:

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1. Effective band placing of fertiliser in wet soils to improve the

uptake of nutrients.

2. Breaking up of shallow compact levels.

It is important that the spring pressure on planting equipment is adjusted

according to the soil conditions. The drier the soil, the heavier the pressure

that should applied; the wetter the soil, the lighter the pressure.

2. CONSERVATION TILLAGE SEEDING SYSTEMS

Conservation seeding systems are recommended in all areas where the rainfall

is low and where the risk of wind and/or water erosion is high as a result of the

low clay content of these soils. If conservation systems are implemented

(whether a high or low rainfall region) they should be applied in a crop rotation

system to minimise the risk of soil- or residue-borne diseases.

D) YIELD PLANNING

Step 1: Weed control (when wet enough) with a rolling rod or

sweep cultivator, depending on the amount of hay that must

remain on the surface.

Step 2: Deep cultivation with a tined implement, to break up

compact layers must be done in March or April. The timing

hereof must be of such a nature that the minimum further

preparation is necessary as each further preparation will

contribute to re-compaction and a loss of hay.

Step 3: Seal the soil directly after cultivation with a tined

implement with a sweep cultivator, harrow or V-blade.

Sept 4: Control weeds with shallow preparation (sweep

cultivator or V-blade) if necessary.

Step 4: Plant according to guidelines and preferably use a tined

planter.

The calculation of the planned yield is one of the first steps to successful wheat

production. The planned yield is defined as a realistic yield that is achievable

in the long term.

Important aspects to consider when calculating the planned yield include

the following:

Available groundwater at planting time. Determining factors include the

amount of rainfall and the distribution thereof before planting time, soil

preparation practices and soil characteristics (such as soil depth and

clay content which have an effect on water storage capacity and rooting

depth).

The amount of supplementary spring rainfall that can be expected.

The general production and management practices applied.

The long-term production history of the specific area.

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Now determine a realistic planned yield according to Table 1. Evaluate the

soil analysis in terms of fertilisation requirements and use the fertilising

guidelines for the specific situation to compile a fertilisation programme.

Table 1: Yield Potential for Dryland Wheat (kg/ha)

Expected rain after

planting 1 (mm)

Moisture depth 2 (cm)

30 60 90 120 150 180 3

10 0 0 158 460 763 1 065

20 0 0 259 561 864 1 166

30 0 57 360 662 964 1 267

40 0 158 460 763 1 065 1 368

50 0 259 561 864 1 166 1 468

60 57 360 662 964 1 267 1 569

75 208 511 813 1 116 1 418 1 720

100 460 763 1 065 1 368 1 670 1 972

1 Expected rain after planting refers to all the rainfall expected from planting

time until physiological maturation.

2 Moisture depth refers to the total depth that can be drilled using an auger or

dug using a spade (up to 1.8 m). The soil should be moist (not merely damp) at

planting time. Regardless of the soil texture, there should be 100 mm/m of

water available to the plant.

3 This table makes no provision for soil with a high water table.

E) FERTILISING GUIDELINES FOR WHEAT PRODUCTION

Fertilising guidelines aim to establish a frame of reference that can be used for

planning a fertilisation programme for a specific situation.

When fertilisation programmes are planned according to guidelines, it is

important that the following be kept in mind:

The prescribed guidelines must be seen as a frame of reference rather

than a recipe for a specific situation. Variations in soil, climate, soil

preparation and management may justify deviations from the guidelines.

These deviations must be motivated by facts.

It is accepted that production practices and managerial capacity is

maintained at a healthy level and that chemical and physical soil

conditions are not limiting factors.

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Soil analyses are necessary and should be carried out before every third

wheat harvest.

1. SOIL ACIDITY

Soil acidity is one of the principal influences for good or bad wheat

production in the summer rainfall area. Fertilisation programmes for

wheat can only be fully effective if the soil acidity does not impede soil

fertility. Acidic soil has a disadvantageous effect on the wheat plant due

to the associated high levels of aluminium in relation to other cations in

the soil. This results in excessive aluminium uptake, which is toxic to

the wheat plant. The root system of the wheat plant very clearly exhibits

the effect of aluminium toxicity. Typical symptoms include the thickening

of the root tips, brittle lateral roots and roots with a brown discolouration.

These symptoms indicate an ineffective root system which restricts the

uptake of water and plant nutrients. The affected plants show typical

drought and nutrient deficiency symptoms and may die off.

Guidelines for liming:

The pH (KCI) and the textural class of the soil are used to obtain an

indication of the lime requirements for wheat production. If the pH (KCI)

is lower than 4.5, pH (CaCl) lower than 5.0 or pH (H2O) lower than 5.5, a

complete analysis must be performed to determine the lime requirement.

The lime requirements are provided in Table 2. The concentration of

aluminium in relation to other cat ions in the soil plays an important role

in determines the reaction of the wheat plant. If the pH values are lower

that 4.5 and/or the percentage of acid saturation is greater than 8%, lime

should be administered.

Table 2: Lime Requirement (ton/ha) for Soils with Variable Acidity Levels

and Clay Contents 1

% Clay

∆ pH > 0.5

∆ AS > 32

∆ pH 0.5 – 0.4

∆ AS 32 – 23

∆ pH 0.4 – 0.3

∆ AS 25 – 15

∆ pH 0.3 – 0.2

∆ AS 15 - 10

∆ pH 0.2 – 0.1

∆ AS < 10

5 – 10 3.9 3.0 2.2 1.4 0.5

10 – 15 4.1 3.3 2.5 1.6 0.8

15 – 20 4.4 3.5 2.7 1.9 1.0

20 – 25 4.6 3.8 2.9 2.1 1.3

25 – 30 4.8 4.0 3.2 2.3 1.5

30 – 35 5.1 4.2 3.4 2.6 1.7

1 Information on determining the lime requirement as published by the ARC

Small Grain Institute in “Guidelines for the Production of Small Grains in the

Summer Rainfall region, 2006.”

Wheat production guide series Copyright 8 PANNAR SEED (PTY) LTD


∆pH – Change in the pH (KCI)

∆AS – Change in the % acid saturation

Soil with a pH of 4 and with a 12% clay content will, in this case, require

3.3 tons of lime per ha to attain a pH of approximately 4.5. If the lime

requirement is greater than 4 ton/ha, it must preferably be applied over

two production seasons. The equation below can also be used to

determine the lime requirement by inserting the desired change in pH

and the actual clay content.

Lime requirement = ∆pH*8.324+0.0459*clay-1.037

Cultivar selection as a short-term solution:

Given that wheat cultivars differ with regards to their levels of aluminium

tolerance, cultivar selection can be used to minimise yield loss. This

must be viewed as a short-term solution and producers must keep in

mind that although aluminium tolerant cultivars will perform better than

cultivars with a weak tolerance to acidic soils, tolerant cultivars also

respond positively to the application of lime. For classification purposes,

wheat cultivars are divided into three groups according to their

aluminium tolerance (Table 3). These groups are referred to as follows:

Excellent tolerance

Reasonable tolerance

Poor tolerance

Table 3: Classification of Wheat Cultivars According To Their Aluminium

Tolerance

Excellent tolerance Reasonable tolerance Poor tolerance

PAN 3355 GARIEP BAVIAANS

PAN 3377 PAN 3434

PAN 3349 PAN 3364

PAN 3118 PAN 3368

PAN 3120

2. NITROGEN FERTILISATION

Nitrogen fertilisation under dryland conditions:

In Table 4 the nitrogen fertilisation guidelines are outlined on a regional

basis as opposed to the planned yield. When using these guidelines,

the following important aspects must be kept in mind:

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All guidelines apply to the cultivation of a wheat crop after a

wheat crop with the assumption that all hay is worked back into

the soil.

Nitrogen fertiliser must be applied at planting time and surface

fertilising is not normally recommended.

High nitrogen fertiliser applied along with the seed may be

unfavourable to germination and therefore also to the final plant

stand. It is thus recommended that no more than 20 kg N/ha is

placed with the seed. Applications higher than 20 kg N/ha must

be applied shortly before planting time or band placed away from

the seed at planting time.

Cultivars with strong seedling vigour should be considered where

wind problems are experienced rather than adjusting the nitrogen

fertilisation to keep the wheat out of the wind.

Although theses recommendations are already adapted to ensure

that the protein content of the grain is satisfactory, adaptation can

be considered when new cultivars with a significantly higher yield

potential than the existing cultivar are planted.

Above average yields accompanied by higher volumes of harvest

residue may contribute to the occurrence of undecayed residue in

the soil at planting time. Late soil preparation and/or wet

conditions during soil preparation could cause a negative nitrogen

period and the associated weakened growth. This may result in

lower yields and downgrading due to lower protein content. With

the appearance or expectance of this situation, the fertilisation

programme must be adapted by increased nitrogen applications

at planting time, or the application of nitrogen (± 15 kg N/ha) and

lime (0.5 ton/ha) during late soil preparation to speed up the

breakdown process.

Table 4: Nitrogen Fertilisation Guidelines (kg N/ha) under Dryland

Conditions According To Production Area and Planned Yield in the

Summer Rainfall Region 1

Producing area

Southern Free State

North-west Free State

Central Free State

Planned yield Nitrogen fertilisation

(ton/ha)

Kg N/ha

1.0 10

1.5 15

2.0 25

1.0 10

1.5 20

2.0 30

2.5 45

3.0 55

3.5+ 2 65+

1.0 15

1.5 25

2.0+ 35+

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Table 4 (continued): Nitrogen Fertilisation Guidelines (kg N/ha) under

Dryland Conditions According To Production Area and Planned Yield in

the Summer Rainfall Region 1

Producing area

Eastern Free State

North-west

Mpumalanga

Limpopo (Springbok Flats

and Dwaalboom)

Eastern Cape coastal area

(East of Humansdorp 3 )

Planned yield

(ton/ha)

Nitrogen fertilisation

Kg N/ha

1.0 15

1.5 30

2.0 40

2.5 50

2.5+ 60+

1.0 5

1.5 15

2.0 25

1.0 10

1.5 20

2.0 30

2.5 40

1.0 0

1.5 10

2.0 15

1.0 15

1.5 20

2.0 30

2.5+ 45+

1 Information on area adaptations as published by the ARC Small Grain Institute

in “Guidelines for the Production of Small Grains in the Summer Rainfall region,

2006.”

2 Valid for the areas around Wesselbron – Viljoenskroon, where a high water

table and good moisture provision can lead to higher yield planning.

3 West of Humansdorp fits in with the winter rainfall area’s southern coastal area

where seed is sown.

Nitrogen fertilisation under irrigation:

Guidelines for fertilising under irrigation such as those included in Table

5 must be adapted when wheat is followed by a leguminous crop as well

as when large amounts of harvest residue is worked back into the soil.

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Table 5: Nitrogen Fertilisation Guidelines (kg N/ha) under Irrigation

According To Planned Yields 1

Planned yield (ton/ha) Nitrogen fertilisation (kg N/ha)

4 – 5 80 – 130

5 – 6 130 – 160

6 – 7 160 – 180

7 – 8 180 – 200

8 + 200 +

1 Information on Nitrogen fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

Under irrigation, applying nitrogen in instalments throughout the growing

season may realise higher grain yields and grain quality with reference

to protein content. A further advantage of applying nitrogen in

instalments is that the planned yield can be adapted throughout the

season depending on climate conditions, yield potential during a given

growth stage or on the water applications. The division of nitrogen

fertilisation across various yield targets on soil with a clay content of 15

– 25% is provided in Table 6.

Table 6: Distribution of Nitrogen Fertiliser throughout the Growth Season

at Various Yield Levels 1

Yield

(ton/ha)

Planting until

tillering stage

Nitrogen division (kg N/ha)

Tillering to

internode

elongation stage

Flag leaf to

flowering stage

4 – 5 80 – 100 30 0

5 – 6 100 30 30

6 – 7 100 – 130 30 30

7 – 8 130 – 160 30 30

>8 160 30 – 60 30 – 60

1 Information on Nitrogen fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

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On soils with lower clay percentages of 25%, the

divisions such as those in Table 6 can be followed.

The application of nitrogen during the flag leaf to flowering stage of plant

development is important to ensure that sufficient nitrogen is available

for kernel growth and development, and for acceptable levels of protein

in the grain. Depending on the yield potential, between 30 and 60 kg

N/ha must be applied in an attempt to increase the protein content of the

grain to above 11%.

3. PHOSPHATE FERTILISATION

There is a variety of phosphate analysis methods available. A

comparison of the analytical values obtained with the various methods

appears in Table 7. The approximate ratios such as those provided in

Table 7 will be valid for most soil types.

Table 7: Ratios (mg P/kg) Determined According To Various Analytical

Methods 1

Ambic 1 Bray 1 Bray 2

Citric acid

1:20

Olsen

6 6 9 10 4

8 10 13 15 6

11 14 18 20 8

13 17 22 25 10

16 20 26 30 12

20 24 31 35 14

23 28 36 40 16

26 31 40 45 18

30 34 45 50 20

1Information on phosphate fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

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Table 8: Phosphate Fertilisation Guidelines (kg P/ha) under Dryland

Conditions According To Planned Yield and Quality of Soil Phosphate

using the Bray 1 Analysis Method 1

Planned yield

Soil phosphate quality (mg/kg)

(ton/ha)

30

1.0 6 5 4 4

1.5 9 8 6 5

2.0 12 12 8 7

2.5+ 18 15

1 Information on phosphate fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

2 Minimum amounts that should be applied at the lower levels of soil phosphate.

With the interpretation of the phosphate fertilising guidelines for both dryland

and irrigation wheat, the following must be kept in mind:

With phosphate fertilisation, reference is made to citric acid or water

soluble sources.

Guidelines are compiled in accordance with economic principles and the

amount of phosphate fertiliser as included in the guidelines is the

amount on at which the maximum gross profit should be earned.

The guidelines make provision for a moderate accumulation of soil

phosphate at low levels of soil phosphate – if the wheat hay is not

removed from the land. A gradual, rather than a once off accumulation

process is supported by band placing phosphate fertiliser during the

planting process.

The higher phosphate fertilisation recommendations in the guidelines

correlate with the lower analytical values and vice versa. For the

analytical values between these limits, the correct phosphate fertilisation

must be deducted within the given amounts of phosphate fertilisation.

Under acidic soil conditions yield increases may be realized when

applying phosphate although high soil phosphate levels exist due to the

relatively lower availability of residual soil phosphate.

Table 9: Phosphate Fertilisation Guidelines (kg P/ha) under Irrigation

According To Planned Yield and Quality of Soil Phosphate using the Bray

1 Analysis Method 1

Planned yield (ton/ha)

Phosphate soil quality (mg/kg)

30

4 – 5 36 28 18 12

5 – 6 44 34 22 15

6 – 7 52 40 26 18

7+ >56 >42 >28 21

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1 Information on phosphate fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

4. POTASSIUM FERTILISATION

Local soils are reasonably rich in potassium and an increase in grain

yields is seldom realised by an increase in potassium fertilisation.

Conditions under which a potassium deficiency may appear include:

High alkaline sandy soil with low inherent soil potassium.

Cold and/or wet and/or dry soil conditions.

Very high content of magnesium and/or calcium levels in the soil.

Potassium fertilisation under dryland conditions:

The analytical values of soil potassium (as opposed to the planned yield)

are listed in Table 10 to illustrate the necessary potassium fertilisation.

The recommendation applies to soils with a clay percentage of >35%.

Where the clay percentage is


19

Table 11: Potassium Fertilisation Guidelines (kg K/ha) under Irrigation

According To Soil Potassium Status and Planned Yield 1

Planned yield (ton/ha)

1 Information on potassium fertilisation as published by the ARC Small Grain

Institute in “Guidelines for the Production of Small Grains in the Summer

Rainfall region, 2006.”

5. MICRO-ELEMENTS

Potassium analysis (mg/kg)


Table 12: Plant Analyses Values of Wheat at the Flag Leaf Stage 1

Element Low (deficient) Marginal High (sufficient)

N (%) 4.2

P (%) 0.5

K (%) 1.6

S (%) 0.4

Ca (%) 0.2

Mg (%)


21

Conditions during and just after application:

Environmental factors such as air moisture and plants that are under

stress are determining factors in the effectiveness of herbicides.

Favourable environmental conditions during spraying will oppose the

detrimental effect of antagonistic salts in the water. In contrast,

unfavourable conditions will compound the harmful effect of salt in the

water. Environmental conditions therefore play a large role in the uptake

of herbicides and the effectiveness thereof. Very poor weed control can

be expected when salt sensitive herbicides are mixed in poor quality

water and sprayed on stressed plants under low air humidity conditions.

Water volumes:

The higher the water volume per hectare with which the herbicides are

applied, the more salt there is to react with the herbicide. The opposite

applies with low water volumes. Although lower water volumes in theory

mean that the herbicide should work more effectively when there is salt

in the water, producers should rather adhere to the recommended water

volumes as far as possible.

Herbicide dose:

The dosage recommended on the label must be used.

Adjuvants:

On the labels of some herbicides the water quality is quantified in terms

of the pH of the application water. The pH is an expression of the

hydrogen-ion concentration in the water. If the herbicide is pH sensitive,

an efficient buffer or acidifier must be added until the optimal pH levels

are obtained.

Buffers or acidifiers are usually added to the irrigation tank before the

other components.

Threshold values:

As a guideline, antagonism can be expected if the combined calcium

and magnesium concentration of the water exceeds 100 mg/l (100

d.p.m.). The same norm can be used for the sodium concentration.

These threshold values are only estimates and depend on how the

abovementioned factors vary.

G) INSECT CONTROL

Wheat cultivation is subject to the appearance of various insect pests. Pests

not only differ in their economical importance, but the stage of development of

the wheat plant can also be a determining factor in deciding whether control is

necessary or not.

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1. APHIDS

The Russian wheat aphid is considered the most important aphid where

dryland wheat is cultivated, especially in the central and eastern Free

State. Aphids can reach plague proportions if the necessary control

measures are not in place. Other plant aphids such as the common

wheat aphid, oat aphid, brown ear aphid and rose grain aphid occur

sporadically and are seasonal in nature.

Russian wheat aphid:

The Russian wheat aphid is a small (30% which may occur on late/spring plantings in the eastern

Free State or under very dry conditions in the western parts of the Free

State. Re-infestation of wheat that was sprayed early may occur during

the susceptible period and subsequently need a follow-up spray, while

spraying after GS 12 is too late and damage will only be partially

avoided. The infestation levels at specific yield potentials that justify

spraying are shown in Table 13. There are seed treatments and

systematic soil agents registered for the control of early aphid

populations and some of these agents are effective for a period of

approximately 100 days.

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Resistant cultivar opposed to susceptible cultivar

Table 13: The Maximum Acceptable Infestation Levels at Various

Yield Potential Levels of Wheat

Yield potential (ton ha -1 )

Aphid infestation at GS 12

(% Plants)

>2.5 ≥4

2.0 – 2.5 ≥7

1.5 – 2.0 ≥10

1.0 – 1.5 ≥14

Other aphids: Aphids that appear sporadically in the summer rainfall

areas are the oat aphid, English grain aphid and rose grain aphid.

These aphids usually flourish under damp conditions and thick plant

densities that appear in irrigation fields, but may also appear during high

yield potential years under dryland conditions. The general guideline for

the application of control measures for these aphids is when 70% of the

tillers are infected with 5 to 10 aphids per tiller. In practice, these aphids

often only appear in severely infected spots within a land from where the

entire land can then be infected. Aphids are also often associated with

the carry over of viral diseases such as the yellow barley dwarf virus to

the wheat plant that in turn leads to the dwarfing and yellowing of the

plant and the consequent lowering in yield potential. Suggested

threshold values for the control of these aphids do not always take the

aforementioned into consideration. To ensure effective control and to

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avoid possible yield loss, the label prescription must be followed during

chemical control of aphids.

The oat aphid is a dark green, pear-shaped aphid with a reddish area

between the siphunculi on the rear end of the aphid, whereas the

English grain aphid appears in two forms, a brown and a green. The

prominent distinction here is that the siphunculi at the rear end are long

and pitch-black in colour. The rose grain aphid is light green in colour

with a dark green line on its back and the siphunculi are long and the

same colour as the body.

2. OTHER INSECT PESTS

Here follows a summary of insects that are regarded as secondary

plagues that appear sporadically on small grains in the summer rainfall

region.

Brown wheat mite:

The brown wheat mite is a small, dark brown, slightly oval shaped mite

with a pair of front legs visibly longer than the hind legs. Mites spend

the evening in or under the soil and inspections must be carried out

during the warm afternoon when the mites are normally most active.

Eggs are laid in the soil and remain dormant until the first light rains

appear in July to August. Dry conditions, after the eggs have hatched,

are favourable for the appearance of large numbers of mites. Speckled

leaves are an indication of infestation as the feeding mechanism of the

mite is designed to remove plant sap from the leaves. With severe

infestations, leaves may turn a yellow/ brown colour; chemical control

can be considered with the appearance of yellow and/or brown spots.

Damage caused by the brown wheat mite is more noticeable when the

plant is under stress. These conditions are detrimental to the uptake

and translocation of insecticides. Producers must be aware that rain

storms of 12 mm or more can drastically lower the mite population,

which makes chemical control unnecessary.

False wireworm:

The false wireworm is the larva of large, black coloured beetles with long

legs which allow them to run fast on the soil surface and hide under

plant material. The larva is the most damaging stage of this pest and

feeds on the seed, roots and seedling stems. Secondary infestation by

fungi such as Fusarium on damaged plant parts may lead to crown and

root rot. The false wireworm larva can be as long as 20 mm and is

distinguished by a hard, smooth body with a gold-brown to dark brown

colour and a sharp tail that points upwards. Seed treatments can be

effective where seedlings grow actively in moist soil.

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Bollworm:

The adult moths are light brown to grey in colour and have a wing span

of approximately 20 mm. The moths fly at sunrise and sunset and lay

their eggs directly on the plant. The young larvae of previous

generations feed on the chlorophyll of the leaves and later migrate to the

spike to feed on developing grain. The colour of the final stage larva

can vary from bright green to brown and it has a distinct white lateral line

on both sides. The larva can get as long as 40 mm and can cause

considerable damage. Direct as well as indirect yield losses can occur

on account of damaged grain with the consequent downgrading of the

grain. The presence of the bollworm is usually only noticed in the spike

when the larva reaches the mid-instar stage. Producers must regularly

inspect their lands for young larvae as the larger, older larvae are

usually less susceptible to insecticides and can cause considerably

more damage. Under dryland conditions, chemical control can be

considered when three to four larvae are found per walking meter.

Under irrigation, the threshold value is six to seven larvae per walking

meter. Only registered chemical agents must be applied and the label

instructions must be followed.

Black maize beetle:

The adult beetle is black, approximately 12 to 15 mm long with strongly

developed wings that enable the beetle to fly over long distances. The

female beetle lays approximately seven to ten eggs in the soil and the

larvae develop in three instars, followed by a pupal stage. The adult

beetles inflict the most damage. The larvae survive on organic material

in the soil. Beetles chew on the base of the seedling stem which causes

a decline in the stand. Given the mobility of the adult beetle, seed

treatment agents are registered as a pre-planting method of adult beetle

population management.

Leafhoppers:

The plague status of leafhoppers is greatly attributed to the fact that

these insects can transmit maize streak virus from infected maize or

certain grass species. Virus transmission usually occurs on early wheat

plantings that are planted near infected grass, maize or self-sown maize.

Young wheat plants that are infected with this virus have a dwarfed

appearance with curled leaves that have thin, well defined chlorotic lines

running parallel to the leaf veins. There are no chemical agents

registered for the control of leafhoppers on wheat. Infestation can be

avoided by later planting away from maize. The alternative is to

consider wheat cultivars that are tolerant to maize streak virus,

especially in areas or under practices where the risk of virus

transmission is high.

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H) DISEASE CONTROL

Fungal diseases on wheat can be controlled by planting resistant cultivars or by

the use of chemical agents. Chemical control can be applied when susceptible

cultivars are planted as well as when once resistant cultivars loose their

resistance due to the development of new pathogenic types of a specific fungal

disease with the ability to overcome the resistance mechanism of a cultivar.

The use of certified seed that is treated against seed-carrying diseases such as

loose and stinking smut also play an important role in the control of seedcarrying

diseases in wheat.

THE RISK OF FUNGAL INFECTION

It is very important that producers are aware of the risk of fungal infection in the

various production areas. The risk in high risk regions can be minimised by

including resistant cultivars in the cultivar package. When susceptible cultivars

are planted in high risk areas, producers must be aware of the disease

symptoms, favourable environmental conditions and threshold values for

chemical control of the various diseases.

Table 14: The Risk of the Occurrence and Outbreak of Rust Epidemics in

the Wheat Production Areas of the Summer Rainfall Region

Production area Stem rust Leaf rust Stripe rust

Western Free State LR 2 LR LR

Central Free State LR LR LR

Eastern Free State LR LR HR

KwaZulu-Natal HR 3

HR HR

Mpumalanga LR HR HR

Gauteng LR LR LR

Limpopo LR LR LR

Northern Cape LR LR LR

1 Where wheat is planted under full or supplementary irrigation the risk of the

development of leaf disease such as leaf rust and stripe rust is heightened.

2 LR = Low risk; 3 HR = High risk

CHEMICAL CONTROL OF FUNGAL DISEASES

A variety of fungicides are registered for the control of leaf diseases in wheat.

The active ingredients of the agents are divided into three groups, namely

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triazole, imidazole and benzimidazole. Rust and leaf-blotch diseases are very

effectively controlled by most triazoles. Certified seed is treated with

fungicides, which are registered as seed treatment agents for the control of

loose and stinking smut.

To successfully apply chemical control measures in wheat, producers

should take the following factors into account:

Climate conditions play a very important role in disease development.

Consecutive favourable periods for disease development will contribute

to disease progression and subsequent epidemic development on

susceptible cultivars. Most fungal diseases flourish in wet years when

there is good bio-mass development and the potential is high.

Chemical control must not be delayed unnecessarily when wheat is at

the flag leaf stage, especially with leaf diseases that progress rapidly,

such as stripe rust. The degree of cultivar susceptibility, yield potential,

growth stage and the incidence of the disease in the field or in the region

as well as prevailing climate conditions must be taken into consideration.

The residual effect of most fungicides that are applied as foliar sprays is

about three to four weeks. The efficacy of fungicides can be placed

under pressure when effective control is not achieved with spraying due

to poor spraying conditions or under conditions of continuous disease

pressure from nearby lands.

In the case where an earlier application (before the eight leaf stage) was

necessary, a second application may be necessary should the

environmental conditions continue to be favourable for disease

development after the three to four week residual effect.

Diseases are not all equally damaging and the economic importance of

diseases such as powdery mildew for example must also be taken into

account.

When wheat is planted in a high risk area of a specific disease,

consideration can be given to more disease tolerant or resistant

cultivars.

If a specific disease appears on a cultivar that is marketed as a resistant

cultivar it must be reported to the company involved. The appearance of

more severely infected spots of a disease such as stripe rust in a land

that is planted with a resistant cultivar, can suggest that the pathogen

overcame the resistance. Resistant cultivars must therefore, as with

susceptible cultivars, be monitored for the appearance of disease

symptoms.

Chemical control as seed treatment is often not effective against soilborne

diseases due to the extended growing period in which the wheat

plant is exposed to such soil-borne pathogens. Soil-borne diseases can

be managed by applying crop rotation and by ensuring that soil factors

such as compaction, which may place stress on the plant, is neutralised.

Self-sown wheat and wheat stubble that appears on the soil surface

often serve as carriers of leaf diseases.

Keep to the registered dosage and further label prescriptions to increase

the effectiveness of chemical control.

Wheat production guide series Copyright 8 PANNAR SEED (PTY) LTD


ROOT DISEASES

Take-all (crater rot):

Take-all is an important root disease in wheat and is caused by a soil-borne

fungus. The disease is especially prevalent where wheat is cultivated in

monoculture systems under irrigation. During wet seasons take-all can also

appear on dryland wheat. Large yield losses can occur when the necessary

management practices are not in place to prevent take-all. The symptoms

include plants with fewer tillers, plants that die before the flowering stage and

the appearance of plants with white spikes in spots in the land. The roots and

crowns of infected plants are black in colour and break off easily due to the

rotting that has taken place. The risk of take-all can be reduced by crop

rotation with alternative crops such as lupin, canola and oats. Grass weeds

and other crops such as barley can also serve as carriers of the take-all

fungus.

Take-all at an advanced stage

Crown rot:

The disease emerges when fungi from the Fusarium genus infect the crowns of

the wheat plant and thereby causes crown rot. Although these fungi are

naturally present in soils, they will proliferate under a monoculture wheat

system. The first above-ground symptoms of this disease often only become

evident after flowering when tillers and spikes die off early. Crown rot mainly

emerges on dryland wheat that is under moisture stress. The disease can also

emerge secondarily on plants that are under stress as a result of primary root

infection by the take-all fungus. Spikes that die off early appear white and will

either not be filled at all or contain shrivelled grain. The crowns of infected

plants appear dark brown in colour and, with variable moisture conditions, the

leaf veins of infected crowns show a conspicuous pink to purple discolouration.

No chemical agent is registered against crown rot. Although all cultivars are

susceptible, there can be differences in their tolerance to crown rot. Crop

rotation and cultivation practices aimed at moisture conservation can lessen

the risk of the occurrence of crown rot.

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STEM, LEAF AND SPIKE DISEASES

Stripe rust or yellow rust:

The disease-causing fungus is an obligate parasite and can therefore only

survive on living plant material. This disease is airborne. Typical symptoms

include elongated, bright yellow to orange stripes which consist of rust pustules

that run parallel to the leaf veins. The stripe formation is less distinguishable

on the younger leaves and the rust pustules appear more in spots on the leaf.

Under very favourable conditions for the development of stripe rust, the leaf

veins, glumes, beards and young kernels can also be infected. The fungal

spores need moisture and low temperatures for germination and subsequent

infecting of susceptible plants. Areas with night and/or day temperatures of

less than 15°C which is coupled with regular dew, mist, rain or over-head

irrigation during the wheat season is regarded as a high risk area. Evening

temperatures above 15°C, with associated day temperatures of 25°C to 30°C,

will have an inhibiting effect on stripe rust development. Various triazolecontaining

agents are registered against stripe rust. Chemical control must be

applied after correct disease identification, confirmation of cultivar susceptibility

and with accompanying favourable environmental conditions for the spreading

of the disease.

Typical symptoms of stripe rust

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Resistant cultivar opposed to susceptible cultivar

Leaf rust or brown rust:

The leaf rust-causing fungus is air-borne and can be identified by the reddish

brown rust spots that appear on the leaves and leaf veins of the wheat plant.

This disease develops rapidly on susceptible cultivars when periods of dew or

misty conditions prevails which last longer than six hours with accompanying

temperatures of 15 to 22°C. During consecutive favourable periods for

infection the epidemic outbreaks can appear within a few weeks of the first

infection of susceptible cultivars. The risk of leaf rust can be managed by

cultivar selection. When chemical control is used, it is important to protect the

flag leaf.

Stem rust or black rust:

The fungus responsible for stem rust is air-borne and distinguished by the

appearance of large, elevated reddish brown rust spots on the leaves, leaf

veins, ears, beards and stems of susceptible cultivars. A more typical symptom

of stem rust is the appearance of elevated, oval shaped, reddish brown spots

on the wheat tillers and/or peduncle. Infection will take place when dew and/or

misty wet conditions are accompanied by temperatures of 15°C to 24°C. Due

to its preference for higher temperatures, stem rust usually appears later in the

season when the wheat plant is already in the grain filling stage. Under

favourable conditions for the development of stem rust an entire yield loss can

occur. The risk of rust infection can be minimised by planting resistant

cultivars. Chemical control of stem rust can only be successful if the tiller area

is covered properly with the fungicide.

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Severe infection of stem rust

Fusarium head blight:

Fusarium head blight is caused by fungi of the genus Fusarium where

Fusarium gramenearum is identified as the primary disease-causing organism

under local conditions. This disease is especially prevalent in irrigation

systems where wheat is alternated with maize, but can also occur during wet

seasons under dryland conditions. Infection of one or more glumes in the spike

during flowering and further spreading of the fungus to adjacent glumes can

cause parts of the spike turn white or "bleach" and die off early. The result is no

grain at all or small, shrivelled kernels on infected parts of the ear. Under wet,

humid conditions, there may be a pink discolouration of infected parts of the ear

due to fungal growth. Optimal conditions for infection and spreading include

temperatures between 15°C and 25°C accompanied by wet conditions and

relatively high humidity. The most effective way to avoid Fusarium head blight

is by crop rotation with non-host crops as well as the destroying of wheat and

maize stubble. Preventative ear spraying during flowering can help to lower the

infection to inhibit disease development.

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Fusarium head blight infection

Glume-blotch:

Glume-blotch is caused by a fungus and symptoms may appear on the leaves

and ears. The disease is found mainly in the eastern Free State and KwaZulu-

Natal. Lesions usually appear on older leaves, are brown, lens shaped and

encircled by necrotic and/or chlorotic leaf tissue. Depending on cultivar

susceptibility the symptoms may differ from cultivar to cultivar. A characteristic

symptom on the ears is the appearance of brown spots. Conditions favourable

for disease development include periods of six to seven hours of dew and/or

rain accompanied by high humidity and temperatures above 7°C. Glumeblotch

is at its most damaging when infection occurs between flag leaf

emergence and flowering. Cultivar resistance, crop rotation, removal of harvest

residue by ploughing or burning and chemical control can help to control the

disease.

Maize streak virus (“Kroeskoring”):

Maize streak virus is transmitted to wheat by leafhoppers from infected maize

and/or grass species. The symptoms on susceptible wheat plants are

described as “kroeskoring”. Plants that are infected at an earlier stage have a

dwarfed appearance and will form fewer tillers with smaller spikes. Chlorotic

lesions that form on infected leaves later converge to form well defined yellow

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lines that run across the length of the leaf. Resistant or more tolerant cultivars

can be used to limit the damage caused by the maize streak virus.

Powdery mildew:

Symptoms of powdery mildew include white to grey cotton-like fungal growths

on aboveground plant parts. This fungal disease typically occurs on the leaves

of the plant, but may also be found on the stems and the spikes under epidemic

conditions. The disease will progress under cool, cloudy and humid

environmental conditions as well as within a dense plant population. Cool

temperatures (15°C to 22°C) and cloudy, humid conditions are ideal for the

development of powdery mildew. The disease can cause yield loss if infection

takes place at an earlier stage and conditions remain favourable for the

development of epidemic conditions before spike development.

SMUT

Karnal bunt:

Karnal bunt is caused by a smut fungus and is seed- as well as air-borne. This

disease is currently limited to irrigation areas of Douglas and Prieska.

Favourable conditions for the development of Karnal bunt include day

temperatures of 16°C to 23°C and night temperatures of 7°C to 11°C. A

relative humidity of more than 70% or a minimum relative humidity of more that

48%; rainfall or irrigation over a few consecutive days during spike

development will also contribute to infection. Typical symptoms include

infected kernels with a black appearance due to the presence of teliospores, a

distinctive weathered appearance and the smell of rotten fish. For the control

of Karnal bunt, it is important that producers use certified seed. Seed can be

treated with Anchor Red (active ingredient is carboxin). This fungicide has the

ability to kill spores which serves as a precautionary measure. Spike spraying

with triticonazole (Tilt ® or Bumper ® ) during the appearance of the spike can

suppress infection to acceptable levels. The first application must be applied at

25% spike appearance with a follow-up spray 10 days later.

Loose smut:

This fungal disease appears in all wheat production regions. Typical symptoms

of loose smut can be observed after spike appearance. Infected spikes are

visible as black to dark brown spore masses which have replaced the spikelets.

When spores have been blown or washed away only the rachis remain. Loose

smut development is favoured by cool, humid environmental conditions which

lengthen the flowering period of the plant. This disease can be avoided by the

use of certified seed that has been treated with a fungicide.

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Loose smut after ear appearance

Stinking smut:

Stinking smut occurs in all wheat production regions. The typical symptoms

are visible after spike appearance when kernels are replaced with greyish

brown coloured “bunt balls”. The smut ball consists of a mass of fishy-smelling

powder (spores of the stinking smut fungus). Infected spikes may also take

longer to ripen. Stinking smut can be avoided by the use of certified seed that

has been treated with the necessary chemicals.

I) GRADING AND QUALITY

Currently, according to the law on agricultural products, there is one bread

wheat class with four grades, namely B1, B2, B3 and B4, which is determined

according to the protein content of the grain, the hectolitre mass and falling

number (Table 15). Hectolitre mass and protein content are largely determined

by the area which includes management practices. Hectolitre mass as a

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density parameter gives a direct indication of the potential flour extraction of the

grain sample. The flour extraction is a critical parameter for the miller since it

has an influence on his/her profitability. A high protein content as well as

protein quality is necessary to ensure that the baker can successfully bake

bread that satisfies consumers’ requirement. Falling number is an indication of

the α-amylase enzyme activity in the grain. A high α-amylase activity (low

falling number) is an indication that the starch molecules have already been

broken down into sugars (maltose) to a large extent and such grain in large

volumes is unacceptable for baking purposes.

Table 15: A Schematic Introduction of the Various Classes and Grades of

Bread Wheat

Grade

BREAD WHEAT – CLASS B

Minimum

protein

(12% moisture

base)

Minimum Hlm

(kg/hl)

Minimum falling

number

(Seconds)

B1 12 77 220

B2 11 76 220

B3 10 74 220

B4 9 72 220

Utility 8 70 150

Other class

J) BIBLIOGRAPHY

Anonymous, 1989. Guidelines for crop production. General cultivation of

wheat.

Anonymous, 1989 – 1990. Guidelines for crop production. Fertilisation

guidelines for wheat production.

Anonymous, 1989 – 1990. Guidelines for crop production. Pest control in

wheat.

Anonymous, 1992 – 1993. Guidelines for crop production. General cultivation

of wheat. Co-ordinated instructions: Planned yield of wheat.

Anonymous, 1992 – 1993. Guidelines for crop production. Fertilisation

guidelines for wheat production.

Anonymous, 2006. Guidelines for the production of small grains in the summer

rainfall region. Composed by the ARC Small grain institute, University of the

Free State and SAB Maltings (Pty) Ltd.

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