PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Sanitation.
Avoid carry-over to new crops, remove and
destroy crop debris and infested plant material.
Remove older affected leaves.
If practical completely clean the production area
at the end of the crop. Remove all plant material,
including weeds, for a week or more.
Control broadleaf weeds around crops and
greenhouses as SWF has a very wide host range.
Biological control.
Natural controls include many predators, parasites
and diseases. Some overseas examples.
– Ash whitefly. A small parasitic wasp, Encarsia
inaron, provides good control in the USA and NZ.
– Computer programs, eg Biocontrol-Poinsettia,
helps growers overseas calculate how many wasps
they should release and how often.
– The fungal diseases BotaniGard , Naturalis -L
(Beauveria bassiana) and Verticillium lecanii can
be used while populations are still low.
Commercial biocontrol agents.
– Predatory lacewing (Mallada signata).
– Greenhouse whitefly wasp parasite (Encarsia
formosa), a tiny introduced parasitic wasp, 0.5 mm
long, lays one egg inside the body of the 4 th stage
whitefly nymph. When hatched the wasp larva feeds
inside the whitefly nymph which turns black within a
few days (unparasitized nymphs are white; when the
wasp, Eretmocerus, lay its eggs under young scale,
the host darkens then yellows). Wasp larva pupate
and after 3-4 weeks, the adult wasp emerges by
cutting a round hole through the upper surface of the
nymph. Infestations are often kept in check and plants
should be examined for parasitized nymphs since
chemical treatment may not be necessary.
In greenhouses, Encarsia is often killed by
sprays used to control other pests, eg aphids, and
does not work well in hairy or sticky leafed crops.
The 1 st , 2 nd and 3 rd stage nymphs may also be
parasitized but are unsuitable hosts and nymphs
of the whitefly and larvae of the wasp die.
In greenhouses, temperatures > 22 o C must be
maintained if Encarsia is to be successful in
reducing whitefly populations. At temperatures
< 22 o C whitefly development is considerably
faster than that of Encarsia.
Encarsia can take 10 days after an initial release to
exert its full effect. About 80% of nymphs must be
parasitized before new releases can be stopped.
Encarsia is more successful in controlling GHWF
than SLWF.
Lucid keys - www.lucidcentral.com/ What Wasp
is That?
List of suppliers www.goodbugs.org.au
Table 34. Whiteflies generally - Some insecticides.
What to use?
FOLIAGE TREATMENTS
Group 1B, eg Rogor , various (dimethoate), Folimat
(omethoate), Lancer , Orthene (acephate)
Group 3A, eg Baythroid (cyfluthrin), Jury , Talstar ,
Procide , various (bifenthrin), Tempo Residual
(beta-cyfluthrin)
Group 4A, eg Confidor (imidacloprid), Crown (acetamiprid),
Actara (thiamethoxam)
Group 7C, eg Admiral Insect Growth Regulator (pyriproxifen)
SLWF & GHWF on
Group 12A, eg Pegasus cotton & some vegetables
(diafenthiuron) suppresses SLWF in
cotton with minimal disruption to natural enemies.
Group UN, eg Neemtech (azadarachtin)
Spray oils (immature stationary whitefly), eg Pestoil ,
White oil (petroleum oil), Bioclear , Biopest ,
Ecopest oil (paraffin oil), Eco-Oil (botanical oil)
Soap sprays, eg Natrasoap (potassium salts of fatty acids
Various Garden sprays, eg Beat–a-Bug (chilli/garlic/
pyrethrin/piperonyl butoxide), also pyrethrin,
bioallethrin, bioresmethrin
SOIL TREATMENTS
Group 4A, eg Confidor Guard Soil Insecticide (imidacloprid)
for SLWF on certain vegetables. Permit required
Resistant varieties. Use if possible, cultivars
with hairy leaves and toxic sap which are
considered to slow whitefly development.
Plant quarantine.
GHWF is spread throughout Australia. Inspect plant
material before introducing it into growing areas.
SPWF. Quarantine areas have been declared in
some regions for SPWF which prohibit and
regulate movement of SPWF-infested and
uninfested plants, plant materials and fruit, out of
Quarantine areas without an inspector’s approval.
Interstate Certification Assurance (ICA)
Operational Procedures, Property Freedom for
Spiraling Whitefly (ICA-36), covers certification
of property for live plants and parts of plants
including plant parts intended for propagation,
leafy vegetables and cut flowers and foliage.
Inspection and Treatment of Plants for
Spiraling whitefly (ICA-35) is in preparation.
Pest-tested planting material.
Inspect new plant material before introducing it to the
main growing area/greenhouse. Use hand lens.
Physical a mechanical methods.
Yellow plastic sheets or fluorescent painted
boards, covered with clear sticky grease attract
whiteflies which stick to the surface when they
land. Clean boards regularly and re-coat with the
sticky material. Useful for small areas outdoors, in
glasshouses and if pesticides cannot be used. To
avoid catching parasites keep traps above plants.
Small outbreaks can be dispersed by hosing.
Greenhouse screens with a pore size 400 m
(micrometers) or less, prevent adult whiteflies
moving in from infested areas. Screens are
expensive and these will not screen out WFT.
UV blocking plastic being researched. Different
types of UV reflective mulches.
Destroying nests of ants feeding on honeydew
will assist parasites and predators to do their job.
Insecticides.
Spray application must be thorough, as
infestations are mostly on leaf undersurfaces.
Apply to young nymphs and adults. Systemic
sprays may be needed for persistent infestations.
Restrictions on some crops, permits may be required.
Follow CropLife Australia Resistance
Management Strategies as SLWF can rapidly
develop resistance.
Avoid broad spectrum insecticides.
When & how to apply?
Follow CropLife Australia Resistance Management
Strategies. When observed, thoroughly apply to
undersurfaces of leaves. Repeat applications may be
needed as insecticides may not kill eggs. Seek advice
about when is best to spray the crop.
Spray oils and soap sprays suppress development of
eggs, metamorphosis and adult formation. They are
most effective against immature whitefly.
Permits may be required for many situations, eg in
glasshouses.
Few insecticides for glasshouse whitefly control are
predator- and parasite-safe. Admiral and Pegasus
cause minimal disruption of the parasites and predators
of SLWF. Overseas the growth regulator Novaluron
(novularon) has little effect on Encarsia and other
introduced beneficials, also suppresses leafminers, WFT
and some moth pests.
Insects and allied pests - Hemiptera (bugs, aphids, etc) 173