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. Obtain/prepare a plan that fits your situation.
2. Crop, region. Recognize variations.
3. Identification of pest must be confirmed. Consult a
diagnostic service if necessary (page xiv).
4. Monitor pest and/or damage and record results as
recommended (page 39). Check the foliage regularly
for signs of early infestation, especially around May-
June and Sept-Oct. Look for egg galls and small
blisters which indicate that leaf mining is in the early
stages. These may be difficult to detect at first but will
become more obvious with experience. Techniques for
assessing impacts in forest areas are available.
5. Threshold. Do you need a threshold? Have any
thresholds been established? If so, what are they, eg
economic, aesthetic?
6. Action. Take the recommended action when any
threshold is reached at the appropriate time before
significant damage occurs. Chemical control is most
useful when larvae are actively feeding but before
they have caused significant damage. Often by the
time damage is noticed it is too late to spray.
7. Evaluation. Review IPM program to see how well it
worked. Recommend improvements if required.
Continue regular surveillance and assessment of insect
activity is essential for effective pest control. Assess
as objectively as possible whether insecticide
application will produce a benefit and is warranted.
Control methods
Cultural methods. Healthy vigorously
growing eucalypts can usually outgrow damage
caused by insects, so severe insect attack can be a
sign that trees are under stress. Proposed sites for
trees must be suitable for the species to be planted,
eg water availability, seasonal rainfall, soil texture
and structure and depth, site topography and prior
land use. Avoid waterlogged hollows, drought
conditions or excessively exposed sites. Drought is
the major cause of seedling stress so seedlings must
be planted when adequate moisture is available.
Optimum tree spacing with consideration of growth
rates, tree form and proposed silvicultural regime.
Sanitation. Light infestations can be controlled
by cutting off infested portions from small trees
and destroying them. Remove dead or dying trees.
Biological control.
Natural controls. Little birds such as
pardalotes remove larvae from blisters for food.
Parasitic wasps attack and kill larvae and pupae
in infested leaves.
Commercial applications. Some of the
parasitic wasps now being used to control
P. froggatti in NZ, where it was accidentally
introduced are being investigated.
Resistant varieties. Young trees of some
eucalypt species are attacked in some seasons and
in some regions of Australia.
Very susceptible species. Flooded gum
(E. grandis), Sydney blue gum (E. saligna),
southern mahogany (E. botryiodes), swamp
mahogany (E. robusta).
Moderately susceptible. Blakely’s
(E. blakelyi), river red gum (E. camaldulensis),
blue gum (E. globules), sugar gum
(E. cladocalyx), snow gum (E. pauciflora),
manna gum (E. viminalis), swamp gum
(E. ovata), red box (E. polyanthermos), others.
Poor hosts. Grey box (E. microcarpa),
Silverton gum (E. camaldulensis var. subcinerea),
spotted gum (E. maculata).
Provenances. Because of differences in their
chemical and physical make-up, not all
provenances of river red gum are equally
susceptible to attack. In other species, such as
flooded gum, there is as yet little evidence that
provenances or individual trees of the same
species vary in their susceptibility to attack.
In areas susceptible to leaf blister sawfly attack
consider selecting appropriate species or
provenances with some resistance to the pest,
eg Silverton race of river red gum rather than
the susceptible Lake Albacutya and allied
provenances.
Insecticides.
Blisters protect larvae from contact insecticides.
Correct timing of insecticide application is
essential.
Systemic insecticides can give some control
but only consider spraying if blisters are small
and larvae are actively feeding. If pupae (raised
oval lumps) can be seen in most blisters, then
spraying will be ineffective as larvae are no
longer feeding.
Chemicals have a limited role in forest tree
management due to the localized and sporadic
nature of most insect damage. However, they
may be needed in plantations of susceptible trees
such as flooded gum in the 1 st two years after
establishment when trees are 1-3 meters high.
Table 21. Some insecticides for leafminers generally.
What to use?
FOLIAGE SPRAYS
Many products are registered for leaf miners generally, eg
Group 1B, eg Rogor (dimethoate)
Group 5, eg Entrust Naturalyte, Success Naturalyte
(spinosad), see also page 74
Spray oils, eg Pest oil , Summer oil, White oil, DC-Tron Plus,
various (petroleum oil);
BioPest , SK_ENSPRAY (paraffinic oil);
Eco-oil (botanical oil)
Remember, check the plant and the leafminer the
product is registered for use on
When and how to apply?
As larvae are feeding within the leaf, systemic
sprays are more effective than contact non-systemic
ones.
Apply at the first indication of damage during spring.
The use of a wetting agent is considered essential for
effective results when spraying eucalypts.
If there are many blister and exit holes it is too late
to control for this season.
Initiator Systemic Plant Insecticide and
Fertiliser (imidacloprid) improves the establishment of
young eucalypts trees providing, enhancing growth and
protection against damage caused by various insect
pests, including some defoliating insects (note
leafblister sawfly is not listed on the label).
128 Insects and allied pests - Hymenoptera (ants, bees, sawflies, wasps)