PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Control methods
For peach and nectarine trees.
Ants attracted by honeydew and sooty mould will
disappear once aphids are under control.
Cultural methods.
Avoid overfertilising plants, especially with
nitrogen as aphids prefer lush growth.
Control ants as they spread and protect aphids
from natural enemies.
Some plants repel aphids eg chives, garlic,
lavender, mint, pyrethrum, rosemary, tansy,
wormwood.
Sanitation. Remove weeds which can be
alternate hosts in and around nurseries and
greenhouses to reduce breeding sites. Remove
severely infested herbaceous plants.
Biological control.
Natural control. Encourage natural enemies
which attack aphid colonies in spring, however,
they do not usually prevent economic damage.
– Predators, eg hoverfly larvae (Syrphidae), small
birds, eg silver eyes. Ladybird beetles and their
larvae reportedly eat as many as 2,4000 aphids
during their lives. Green lacewing larvae
(Chrysopidae) consume up to 100 aphids/day.
– Parasitic wasps, eg Diaeretiella sp., lay their
eggs in aphid bodies which swell up. When the
adult wasp emerges there is an obvious exit hole,
‘mummies’ may be brown/black (page 152).
– Fungal and other diseases. Various fungi attack
aphids in warm humid weather, eg Aschersonia,
Beauveria, Entomophora, Metarhizium, Verticillium.
– GPA populations are reduced by heavy rain and/or
early leaf fall in autumn.
– If weather prevents returning winged males from
reaching peach trees females will lay infertile eggs.
Commercially available
– Predatory green lacewings (Mallada signata).
– Parasitic wasps (on aphids), eg Aphidius colemani.
– List of suppliers www.goodbugs.org.au
Resistant varieties.
Not practical for tree hosts but may be useful for
secondary hosts, eg lettuce. Lucerne aphids are
now controlled by a combination of parasites,
predators and tolerant or resistant varieties.
Pest-tested planting material.
Use aphid-free planting material as aphids
reproduce rapidly and establish quickly on crops.
Keep parent stock plants free of aphids (and
other vectors) to prevent infection with virus
diseases and to reduce spread of aphids on
propagation material.
Physical & mechanical methods.
Some growers install screens (correct mesh size)
on greenhouse vents to prevent entry of aphids
and other small insects such as thrips.
Squash aphids with fingers by simply wiping
down the sides of affected shoots with your
finger. Wear gloves to avoid stains.
Hosing with water may temporarily remove
aphids from some plants. Aphids tend to return.
Insecticides.
Many naturally occurring or commercial biocontrols
are susceptible to insecticides.
GPA has developed resistance to more than
60 insecticides including several organophosphates,
carbamates and synthetic pyrethroids.
Follow Croplife Australia’s resistance
management strategies and label directions.
Insecticides combined with the activity of aphid
predators in spring are an important component
of the resistance management strategy for green
peach aphid.
Aphicides will reduce impacts on non-target
organisms.
Newer systemic insecticides may be applied
as spot sprays or root drenches and used with
biocontrol agents.
Spot treatment is the preferred application
method, not blanket spraying. Sprays other than
oils will kill large number of predators.
Table 27. Green peach aphid - Some insecticides for use on stone fruit.
What to use?
DORMANT SPRAYS
Spray oils, eg Winter oil (petroleum oil); Bioclear , Biopest
(paraffinic oil) – dormant or delayed dormant
SEMI-DORMANT SPRAYS
FOLIAGE SPRAYS
Group 1A, eg Pirimor (pirimicarb ) – systemic aphicide
Group 1B, eg Malathion (maldison)
Group 4A, eg Confidor , various (imidacloprid); Calypso
(thiacloprid); Samurai , various (clothianidin)
Group 9B, eg Chess (pymetrozine) - not toxic to some
predators
Spray oils, soaps, eg Eco-oil (botanical oils); insecticide soaps
Home garden sprays, eg there are many sprays for aphids
generally on roses and other ornamental plants.
When & how to apply?
Apply to dormant peaches and nectarines no later
than early budswell to kill 'overwintering' eggs.
Limited use as aphids move in from adjacent plants.
Semi-dormant sprays to control young aphids when
hatching is complete.
These sprays can often be combined with other
pesticide sprays which may be necessary at this time.
Trees must have produced some foliage for these
sprays to be effective.
Apply when observed.
Some sprays are toxic to early peaches. Only spray if
monitoring indicates a need (infestation is severe)
and the early budswell oil spray was missed.
Follow resistance management strategies.
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154 Insects and allied pests - Hemiptera (bugs, aphids, etc)