PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
BIOLOGICAL CONTROL (contd)
BY DISEASES
Also known as:
Microbial agents
Microbial pesticides
Biological pesticides
Biocontrol agents
50 MILLION
INFECTIVE
JUVENILES
VIRUSES.
Some viruses only attack insects, eg beetles, grasshoppers, caterpillars. Viruses
can be genetically engineered to increase the speed at which they kill infected insects
(page 88).
Gemstar®, ViVUS Gold (Heliothis virus) is used in IPM programs for corn
earworm (Helicoverpa armigera) and native budworm (H. punctigera) in cotton
and certain fruit, vegetable, ornamental, field crops. The virus is ineffective against
large caterpillars, taking so long to kill the infected host caterpillars that much crop
damage can occur in the mean time. The virus must be eaten.
Other insect viruses, include:
Cabbage white butterfly virus
Codling moth virus
Lightbrown apple moth virus
Potato moth virus
BACTERIA.
Bacillus thuringiensis (Bt) , a soilborne bacterium, is marketed as a ‘biological
pesticide’ to control leaf eating caterpillars with a high gut pH. The caterpillars
eat the bacterial spores which contain a toxin that causes septicaemia killing them.
Different strains of Bt attack different insects (page 59). New strains of Bt are still
being developed. Research is continuing on whether insects may develop
resistance to Bt. Bt. used to control caterpillars of the gypsy moth in Chicago may
also kill caterpillars of many other species.
Dipel ® , various (Bt subsp. kurstaki) - Some leafeating caterpillars, has some
activity against mosquitoes.
XenTari ® , various (Bt subsp. aizawai) - Caterpillars, eg corn earworm or cotton
bollworm (Helicoverpa armigera),
diamondback moth (Plutella xylostella)
- Mosquito larvae
Cybate ® , Vectobac ® (Bt subsp.
israelensis)
Novodor ® (Bt subsp. tenebrionis)
Spinosad (derived from soil bacteria)
Entrust ® Naturalyte ® Insect Control,
Success ® , Tracer ® (spinosad)
- Chrysomelid and tenebrionid beetle pests
in plantation eucalypts, elm leaf beetle
(under research)
- Certain insect pests of certain crops, eg
cotton, vegetables, fruit, ornamentals
Many other bacteria are being researched overseas including Wolbachia
bacteria which could be used to modify natural populations of the dengue fever
mosquito (Aedes aegypti) to prevent it transmiting the virus to humans. Bacillus
firmus is an insect pathogen of some caterpillars.
FUNGI.
Green muscardine fungus (Metarhizium spp.) can be purchased, eg
BioCane ® (Metarhizium sp.) - Greyback canegrub
GreenGuard ® (Metarhizium sp.) - Locusts, grasshoppers
BioBlast ® (Metarhizium sp.) - Termites (in the USA)
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Other fungi which kill a range of insects include Verticillium lecanii,
Beauveria bassiana, Entomophthora, Paecilomyces spp. Overseas also
Aschersonia aleyrodis is being researched to suppress whiteflies.
NEMATODES. Entomopathogenic nematodes (ENs)
Some nematodes are symbiotically associated with bacteria which they carry within
their intestinal tract, often within a specialized vesicle. The nematodes seek out
natural openings on insects and move into the bloodstream where they release the
bacteria causing septicaemia. Most insects are susceptible and given enough nematodes
they will die, eg
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www.ecogrow.com.au/
Beddingia siricidola
Heterorhabditis bacteriophora
Heterorhabditis zealandica
Steinernema carpocapsae
Steinernama feltiae
Steinernema feltiae
- Sirex wasp in Pinus radiata
- Black vine weevil
- Argentine stem weevil, certain scarab
grubs, bill bug weevil
- Banana borer weevil, cutworm,
armyworm, house termites, cat flea
- Currant borer moth caterpillars
- Fungus gnats, mushroom fly
Insects and allied pests - Integrated pest management 43