PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Natural controls. Natural enemies of woolly
aphid have been well documented by Asante
(1997). However, they often do not increase
quickly enough to prevent woolly aphid
populations reaching the threshold level detailed
on page 156.
– Predators in Australia include ladybirds, eg
common spotted ladybird (Harmonia conformis),
transverse ladybird (Coccinella transversalis),
mealybug ladybird (Cryptolaemus montrouzieri),
also lacewing and syrphid fly larvae and earwigs.
– Parasites, eg 5 species of wasps and 2 species of
mites assist in reducing woolly aphid populations.
– Fungal diseases, eg Verticillium lecanii is
reputed to infect woolly aphid.
Resistant varieties.
Malling-Merton series rootstocks with
some resistance to woolly aphid have been
readily available for many years, and trees are
grafted onto these stocks. The use of resistant
rootstocks means that woolly aphid can no
longer multiply on or damage roots and act as a
source of re-infestation and that woolly aphid
has only to be controlled on aerial parts of trees.
Note that even on resistant rootstock a few
aphids may still be found on roots.
Rootstock can be chosen which have some
resistance not only to woolly aphid, but also to
Phytophthora collar rot and fireblight (NSW
Agfact Apple Rootstock Identification).
Northern Spy:
– Is resistant to wooly aphid.
– Is moderately susceptible to Phytophthora.
– Is moderately resistant to fireblight.
– Causes minimal suckering.
– Is tolerant to different soil types.
– Other roots stock may be more susceptible to
Phytophthora, fireblight, etc.
Pest-tested planting material.
Examine purchased nursery stock to check for the
need for treatment prior to planting.
Insecticides. Apples
A dormant spray of winter oil may kill
some ‘overwintering’ aphids in cracks on trunks
and limbs (not very effective) but not Aphelinus.
Growing season sprays should be applied
when infestations are first noticed usually in
spring and autumn when trees are growing
vigorously. Remember,
– Sprays may be toxic to Aphelinus.
– A resurgence of aphids may occur prior to harvest.
Table 28. Woolly aphid – Some insecticides.
What to use?
ROOT OR NURSERY STOCK DIPS
Group 1B, eg Rogor (dimethoate), permit may be required
DORMANT SPRAYS - deciduous trees
Spray oils, none registered for woolly aphid
GROWING SEASON SPRAYS
Group 1A, eg Aphidex , Pirimor , various (pirimicarb) -
systemic aphicide
Group 1B, eg Rogor (dimethoate) - systemic
Folimat , Sentinel (omethoate) – systemic
Malathion (maldison) - non-systemic
Lorsban , various (chlorpyrifos) - non-systemic
Group 4A, eg Confidor , Kohinor , Surefire , (imidacloprid);
Samurai (clothianidin) - systemic
When & how to apply?
Use for nursery trees with gross infection prior to
planting. Severely infested roots or whole plants of
nursery stock may be dipped in insecticide and drained
prior to planting.
Indicates their lack of effectiveness, but does not kill
Aphelinus.
Apply when infestations are first noticed and any
threshold is reached, usually in spring and autumn.
Systemic pesticides give best control and should be
applied when trees are growing vigorously. If trees are
not growing vigorously use contact insecticides.
SOIL TREATMENTS
Group 4A, eg Confidor , Confidor Soil Guard Insecticide
(imidacloprid) - systemic - to conserve Aphelinus
mali use at the reduced rate as recommended on the
label. Commercial growers only.
For trees up to 7 years of age.
During late summer/autumn, mark affected trees for
treatment the following season, ie green tip to petal fall.
If aerial colonies are present, maximum effectiveness
may not be achieved until the following season. Do not
treat any more than once in any 2 year period.
Insects and allied pests - Hemiptera (bugs, aphids, etc) 157