PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
CULTURAL
METHODS contd
Prognostic
rather than
diagnostic
Nutrient deficiencies & toxicities. Maintain appropriate fertilizing, some
nutrient deficiencies and toxicities are common, eg
– Guard against over-fertilization which is common when plants are young.
Overuse of some fertilizers can cause environmental, agronomic, management
and economic problems for many growers. Nitrogen runs out first in nurseries.
– Nutrient charting is a means of obtaining early warning signs of nutritional
disorders and is used to anticipate deficiencies and toxicities so they can be
corrected before they become chronic. It is also used to check on the adequacy
of fertilizer programs and perhaps a guide to a new one and indicate when a
crop needs top dressing. The procedure is prognostic rather than diagnostic.
NGIA Nursery paper www.ngia.com.au
– Identify micronutrient deficiencies with plant tissue, soil and water tests.
– Know your fertilizer source well, eg the pros and cons of them. Is it from
poultry, horses, lofted cattle, pigs or bio-solids which might include human
waste?
– Organic fertilizers programs may provide long-term soil benefits but are not
the answer to immediate crop nutrition needs (Norwood 2010).
– Specific toxicities might apply, eg phosphorus toxicity in certain proteaceous
plants. Cadmium in monitored in fresh vegetables.
– Specific deficiencies may occur in certain areas, eg boron in the southern
tablelands of NSW.
– Understand conditions favouring nutrient deficiencies and toxicities, eg
soil pH, lack of mycorrhiza, nitrogen drawdown in mulches, irrigation practices.
– Tree implants provide phosphate to promote healthy growth/root development,
potassium for cell strength rigidity and other nutrients.
Others cultural controls are infinite.
Postharvest life of
certain fruits could be
extended significantly by
silencing the genes that
make fruit go soft after
ripening. This does not
require the introduction
of foreign genes.
TOLERANT VARIETIES.
Some plant varieties now available have some tolerance to drought, temperature
extremes, saline soil, etc. Many crops have been bred to have multiple resistances.
Possibilities are endless.
Ornamentals, eg purple-leaf cherry plum (Prunus cerasifera 'Nigra') has some
tolerance to warm dry conditions.
Fruit, eg rootstocks of apple (Malling Merton 104 (MM104)) have some resistance
to drought.
Vegetables, eg some varieties of broad bean, eg 'Coles Dwarf Prolific' are less
susceptible to wind damage than others.
Indoor foliage plants can be grouped according to tolerance of low light.
Trees, eg varieties of casuarina, eucalypt, wattle have tolerance to salt. Eucalypts
are bred for salt and stress tolerance.
Turf seed is selected for heat, wear, shade, salt tolerance, grey leaf spot and
brown patch resistance. DNA analysis is used to examine the differences within
the natural selections of kikuyu, DNA can also be used to distinguish genetic
diversity among a wide range of turfgrass, eg perennial ryegrass, buffalograss,
and couchgrass, Kentucky bluegrass. Future work in kikuyu will focus on
resistance to kikuyu yellows and tolerance to a range of environmental stresses.
Salt tolerant plants and crops. There is much ongoing research on how
native and exotic plants and animals cope with different levels of salinity. Some
plants are naturally salt tolerant but they can also be bred or genetically
engineered. Halophytes are salt tolerant plants that grow naturally in salt affected
soil, eg saltbush. The development of salt tolerant crops, eg grass and wheat
hybrids and saltbushes that will tolerate high levels of salt and soil waterlogging,
offer hope to salt-affected land.
Irrigating salt tolerant grasses using saline ground water.
Salt water can be used when fresh water resources are limited. But requires a
well integrated management program to prevent off site impacts etc.
Genetically modified (GE) crops, eg
– Some transgenic cotton has some tolerance to waterlogging, various herbicides
and Helicoverpa caterpillars. Tolerance to drought is also under development.
– Recently a gene involved in the proliferation of roots of certain crop plants
has been identified enabling in crops plants growing in low fertility soils to
develop more extensive root systems.
– Research continues on sugarcane to alter plant growth, enhance drought
tolerance and nitrogen use efficiency, to alter sucrose accumulation or to
improve cellulose ethanol production from sugarcane biomass.
– Genetic approaches and environmental factors may be used to control growth
and flowering.
Non-parasitic pests and diseases 401