PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Pest cycle
There is a complete metamorphosis (egg,
larva, pupa and adult), with many overlapping
generations during spring, summer and autumn.
The life cycle takes about 5-6 weeks for
completion and all stages may be found on the
plant at once. Female beetles deposit eggs in spring
in small groups usually on the lower surfaces of
leaves, where most of the larval feeding occurs.
When fully grown, the larvae congregate in
numbers on the foliage of the food plant or nearby
litter and pupate. The pupae are attached to the
plant or litter at their hind end. The last larval skin
remains attached around the end of the pupa.
‘Overwintering’
As inactive adults.
Spread
By adult beetles flying (although they do not fly
readily, this is their main method of spread).
They may be assisted by wind.
Movement of infested seedlings.
Conditions favoring
High humidity as in coastal or irrigated areas.
October to April. Leafeating ladybirds require
higher humidity than pumpkin beetles so are more
of a problem in coastal areas than inland.
However, in certain irrigated inland areas they can
be a problem, eg Murrumbidgee Irrigation Area.
Management (IPM)
Are you a commercial grower or home gardener?
1. Prepare a plan that fits your situation.
2. Crop, region. Recognize variations.
3. Identification can be difficult so consult a
diagnostic service if necessary (page xiv).
4. Monitor larvae, adults, pest damage and beneficial
insects weekly during the time when damage is
expected, eg examine a prescribed number of potato
plants in a row at several widely spaced locations
throughout the crop. Seek advice if necessary on
monitoring and about the need for monitoring in your
crop and region. Remember if monitoring, you need to
know when and where to look, and what and how
to monitor.
5.Thresholds will vary according to the crop. How
much damage can you accept on your crop? An
example of a threshold might be:
If there is more than an average 25% leaf area lost
on 3 out of 30 potato plants examined, then control
measures should be started (Brough et al. 1994).
6. Action. Take appropriate action when your
predetermined threshold is reached.
7.Evaluation. Review IPM program to see how well
it worked. Recommend improvements if required.
Control methods
Sanitation.
On a few plants in a home garden situation,
adults and larvae may be collected or squashed.
Destroy infested crop debris as soon as possible
after harvest to assist control, though adult
beetles spread by flying.
Biological control.
A few parasitoids and predators attack larvae and
adults. The ‘burry’ larvae may deter some known
parasites and predators.
No biological control agents are available for
purchase and none have been released by
government agencies.
Pest-tested planting material.
Check incoming seedlings for adults and larvae.
Insecticides.
Apply foliage sprays or dusts if monitoring
indicates a need.
Table 12. Leafeating ladybirds – Some insecticides.
What to use?
FOLIAGE SPRAYS AND DUSTS
Group 1A, eg various products (carbaryl is not registered for
use on food-producing plants in the home garden)
Group 1B, eg various products (malathion)
Home garden sprays, eg several containing bioallethrin +
bioresmethrin
When and how to use?
Apply after monitoring or at first sign of infestation,
depending on the situation.
Insects and allied pests - Coleoptera (beetles, weevils) 105