PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Conditions favouring
Warm, dry weather in late spring and early summer
speeds development of eggs and larvae. Warm
autumns increase risk of late infestation.
Optimum temperature 28-30 o C (cycle 4 weeks).
Each stage of the life cycle has specific temperature
requirements for development, eg
– Moths do not mate or lay eggs until the temperature
exceeds 16 o C and air is calm. Moths will not
emerge from pupae, take flight or mate at < 16 o C.
– Eggs hatch, larvae feed and grow and pupate at a
minimum threshold of 10 o C.
– Adult males fly at a minimum threshold of 13 o C.
Good pupating sites on the tree itself.
Management (IPM)
Are you a commercial grower or home gardener?
1.Obtain/prepare a plan based on your legal
obligations in your State/Territory. Growers should
obtain local information on scouting and control
recommendations.
2.Crop, region. Be aware of pest favourable
climates, proximity of other susceptible crops, etc.
3.Identification of codling moth larvae must be
confirmed. Consult a diagnostic service if necessary
(page xiv).
4.Monitor pest and/or damage and record results as
recommended. Monitoring offers direct savings
associated with the cost of sprays, long term benefits
of reducing the numbers of sprays and slows down
development of resistance to chemicals.
Orchards without MD (mating disruption) need
pheronome traps or codling moth warning systems (pages
44, 92). Check infestation at thinning time (if present
review program).
– Monitor male moths. Synthetic female
pheromones are used to attract male moths to
sticky traps where they are counted regularly so
that the number of routine pesticide applications
can be reduced and timing improved.
– Early warning systems have been developed
which issue recommendations on the best time to
spray based on codling moth populations and
daily temperatures recorded by the grower.
The system depends on establishing the first
emergence of moths from ‘overwintering’ sites
and then recording daily temperatures. Records
are sent to the local Departments of Agriculture/
Primary Industries which enters them into a
computer model which gives a prediction of when
egg laying will commence and optimum date(s)
for spraying with an insecticide.
Orchards with MD need to be monitored by
suitably trained staff or a consultant .
– Monitor male moths with sticky male pheromone
traps before moth activity starts so that MD
dispensers can be placed in orchards at the correct
time. However, MD interferes with trap readings.
– Monitor fruit for damage by scouting from
early December to harvest, depending on district.
5.Thresholds. There may be nil quarantine requirement,
eg in WA. How much damage can you accept? Take advice.
6.Action. Decisions about some methods of control,
eg mating disruption (MD), need to be made long
before monitoring has indicated a need for an
insecticide application. Seek expert advice if unsure.
7.Evaluation. Review IPM program to see how well
it worked. Recommend improvements if required.
Record damage at harvest to help with management
decisions for next season.
Control methods
Successful control requires careful hygiene, mating
disruption, insecticide selection and application,
resistance management and monitoring, etc.
www.bioglobal.com.au/
Legislation. Control measures are compulsory
under State/Territory legislation such as Plant
Diseases Acts or their counterparts which require a
grower of apples, pears and quinces in some areas
to carry out certain sanitation treatments and to
apply a minimum number of pesticide applications.
Sanitation. You may be required by law to:
Collect all fallen fruit and remove all infested fruit
from trees at intervals not exceeding 7 days (for
fruit fly the interval is 3 days). Keep ground
beneath trees free from long grass and weeds. Treat
fruit to be destroyed by boiling, burning or placing
in a special insect-proof pit.
Remove and destroy ‘overwintering’ sites, eg
unwanted trees, unwanted litter and plant debris
(boxes, tree props).
Scrape loose bark and cocoons from the trunk and
limbs of the tree during December and again at the
end of February and during winter.
At end of season check bulk bins and other
handling equipment for cocoons in cracks and
crevices, if found destroy larvae.
Home gardeners in isolated areas could remove and
destroy all fruit as it develops for 1 year.
Biological control/Natural controls.
Natural controls do not appear to reduce
codling moth populations significantly.
– Codling moth virus can devastate localized
populations of codling moth larvae. This virus has
been developed into a commercial product overseas
but local trials in Australia have been disappointing.
– A parasitic nematode has shown promise for
control of ‘overwintering’ larvae.
– Earwigs and mirid bugs prey on codling moth
eggs but neither gives significant control.
– Wasps, eg Trichogramma, parasitize codling moth
eggs. In Australia the rate of parasitism is too low
for commercial use.
Commercial use. Male moths are attracted to
females by strong scent (pheromones).
– Female pheromone lures have been used for
decades to attract male moths to sticky traps where
they are counted regularly. This ensures better timing
of insecticide applications, reducing pesticide usage.
Picking up fruit
Monitoring male moths,
some traps attract both
male and female moths
Mating disruption
(tiers are attached
to twigs)
Cocooning sites
Fig. 62. Codling moth (Cydia pomonella). Sanitation, biological methods
(pheromones for monitoring, mating disruption) and physical methods assist control.
Insects and allied pests - Lepidoptera (butterflies, moths) 91