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 2 generations each
season and often a partial 3 rd generation (Fig. 61
below). Multiple generations in warmer districts.
The 1 st (spring) generation moths start to emerge
early in October, reaching a peak about mid-
November. Eggs are laid on leaves and fruit at
dusk when the temperature is 16 o C or higher and
the air is calm. They hatch in 5-10 days, young
caterpillars soon entering into fruit to feed around
the core. They become fully fed in about 4 weeks
when they crawl down at night from the fruit to
shelter under loose bark, in crevices around the
trunk and main limbs to spin cocoons in which
they later pupate. They may fall to the ground in
infested fruit and then look for stable litter, eg
packing cases, on which to pupate. The 1 st
pupation occurs during the 1 st week in December
and continues throughout December and January.
Moths emerge in about 15 days and reach peak
numbers in late January. Larvae from this
generation ‘overwinter’ in a fully fed state in
cocoons and pupate in mid-September. A partial
3 rd generation sometimes occurs, infesting late
varieties in April.
‘Overwintering’
Because adult moths are not very mobile, the main
source of infestation in spring (the 1 st brood
moths) in an orchard or on a tree is the overwintering
cocoons in cracks and under loose bark
on trunks, broken limbs, on stable litter on the
ground, paling fences, packing cases, etc. A few
‘strays’ will wander in from surrounding orchards,
just as a few of the native population will depart,
but their numbers are negligible.
Spread
By adults flying at dusk. In most orchards female
moths will not spread over more than 5-10 trees,
but males will fly as far as 180 meters.
Transfer of fruit infested with caterpillars.
Transfer of cocoons on packing containers or
any other suitable carrier. Because the spread of
codling moth to new areas is by the movement of
infested fruit (larvae) or fruit boxes (cocoons) or
any other suitable carrier, preventing this is an
essential part of quarantine.
Fig. 61. Pest cycle of codling moth (Cydia pomonella).
90 Insects and allied pests - Lepidoptera (butterflies, moths)