PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IPM)
Are you a commercial grower or home gardener?
1.Access a plan in advance that fits your situation.
2.Crop, region. Know variations.
3.Identification. If necessary consult a diagnostic
service (page xiv) as several species of aphids can
attack cabbages.
4.Monitor pest and/or damage and record results. Early
aphid infestations are of greater significance in terms of
potential damage. Different methods can be used, eg
Monitor number of stunted plants. Inspect crop
weekly when aphids are expected. Examine 10 plants
at each of 6 widely spaced locations along a zigzag
route through the crop.
Monitor number of natural enemies of aphids,
eg hoverflies, daily weather conditions.
Satellite mapping. In the UK, aphid populations
can be assessed on Brussell sprouts using satellite
mapping and Geographic Information Systems
(GIS) software. Research also indicates that growers
may only need to monitor the edges of fields
rather than the whole field.
An Aphid Alert service is available in the USA for
insects that affect soybeans. It provides a warning
when aphids are near threshold level, indicating that
it is time for growers to scout their fields and
consider an insecticide application to protect their
crops www.aphidalert.com
5.The threshold is usually an economic threshold.
How much damage can you accept? One suggestion is
to take action if more than 10 out of 30 cabbage plants
plants are infested. In some crops control measures are
recommended (if all the plants inspected have aphids
at a predetermined threshold levels).
6.Action at the determined threshold can be bio-controls,
which do not prevent economic damage and/or
insecticides (see Table 26 below). Where transverse
ladybirds are found in nurseries try to avoid spraying.
7.Evaluation. Review your program, recommend
improvements if necessary.
Control methods
Cultural methods.
Avoid year-round growing of Brassicas.
Site plants away from sources of infestation.
Sow late to avoid aphid flights,
Organic gardeners may use repellant plants such
as garlic to assist with aphid control.
Planting dill near cabbage encourages predatory
hover fly (Syrphidae) larvae.
In the USA, opaque mulches of aluminum and
other reflective materials reduce aphid numbers
on vegetable plants by up to 96% and prevent
weed growth. The aluminum reflects the blue of
the sky and disorientates aphids. In Australia,
plants tend to become scorched.
Intercropping disrupts the visual and chemical
cues that aphids use to locate host plants, ie the
contrast between crop and surrounding soil is
reduced. Intercropping Brussel sprouts with
French dwarf beans or weeds may help reduce
aphid infestations.
Sanitation.
Prompt disposal of harvested crops and control of
Brassica weeds assist control.
Biological control.
Natural controls do not prevent economic
damage.
– Predators, eg common spotted ladybird
(Harmonia conformis), birds, young mantids, mites,
lacewings, spiders, earwigs, hoverfly larvae. Some
ladybirds can consume up to 100 aphids per day
and will feed on twospotted mites if aphids are
absent. Tasmanian lacewing (Micromus
tasmaniae) larvae consume up to 10 aphids per day.
– Parasitic wasps, eg the cabbage aphid parasite
(Diaeretiella rapae) leaves many swollen empty
aphids on plants, each with a small hole through
which the adult wasp has emerged (page 152).
– Various diseases are being researched for
possible use as biological control agents, eg the
fungi, Metarhizium anisoplia and Entomophora.
– Heavy rain can destroy large numbers of aphids.
Commercial biocontrol agents.
– Predators, eg lacewings, ladybirds.
– Parasitic wasps, eg Trichogramma spp.
List of suppliers www.goodbugs.org.au
Resistant varieties.
Use resistant or tolerant cultivars if practical; red
cabbage is reputed to have some resistance.
Plant quarantine.
Not really applicable.
Pest-tested planting material.
Ensure transplants are aphid-free before planting.
Screen seedling houses to exclude aphids prior to
transplanting.
Physical & mechanical methods.
Aphids can be hosed off plants using a strong jet of
water but tend to return quickly.
Insecticides. Table 26 below.
Table 26. Cabbage aphid – Some insecticides.
What to use?
FOLIAGE SPRAYS AND DUSTS
Group 1A, eg Aphidex , Pirimor , Ospray (pirimicarb) -
systemic aphicide
Group 1B, eg Eraser , Lancer , Orthene (acephate)
Group 3A, eg Ambush , Pounce (permethrin)
Group 4A, eg Confidor , various (imadicloprid)
Group 9B, eg Chess (pymetrozine) - not toxic to predators
Group 21B, eg Derris Dust (rotenone)
Spray oils, eg Bioclear (paraffinic oil); Eco-oil (vegetable oil)
House and garden sprays and dusts for aphids generally,
eg soap sprays, pyrethrin, Derris Dust (rotenone)
SEED TREATMENTS
When & how to apply?
When observed.
Insecticidal soap may be phytotoxic under some
conditions especially to Brussel sprouts and cabbages.
Observe label withholding periods for edible crops.
Group 4A, eg Picus Seed Treatment (imadicloprid)
protects seedlings of certain crops (cotton, canola and
cereals) from early aphid injury caused by other aphid
species and in some instances, spread of virus diseases.
Insects and allied pests - Hemiptera (bugs, aphids, etc) 151