Pheromone traps
The flight activity of male moths should be monitored using sex pheromone traps. The delta trap design is used widely.
- Traps should be set out in orchards shortly after blossom (where the fruitlet mining tortrix is a problem locally, codling moth traps, which also attract males of the fruitlet mining tortrix, should be set out before blossom).
- Ideally, each orchard should be individually monitored with at least one trap.
- The traps should be hung from the branch of the tree at canopy height in the centre of the orchard and oriented to allow air flow through the trap by the prevailing wind.
- The number of moths caught in each trap should be recorded weekly and the dead moths removed.
- Lures should be changed every 4-6 weeks as recommended by the manufacturer. A 4 week interval is better in hot weather. Sticky bases should be changed when their effectiveness declines significantly.
- The usual threshold for chemical treatment is a single catch of 5 or more moths per trap per week from May to July (first generation, fruit less susceptible) and 3 per trap per week from August to September (second generation, fruit more susceptible). Treatment with codling moth granulovirus may be necessary before these thresholds are reached.
Egg counts
AHDB Horticulture funded research (Project TF 189) showed that pheromone trap catches don’t give a good indication of when the pest is actually laying eggs in apple orchards. Instead, regular egg counting on fruitlets is probably the only fully reliable and accurate way of determining whether and when an orchard needs spraying, but it’s time consuming and unlikely to be done by growers or their consultants.
An alternative way of predicting when egg laying has occurred is to use the RIMpro-Cydia forecasting model in conjunction with sex pheromone monitoring traps (see below).
Fruit damage
Inspecting fruits for damage either whilst developing on the tree or at harvest or grading, may indicate if populations are high and damage is likely from the next generation.
- Dropped fruits on the ground under the tree may also be examined in summer.
- Damage exceeding 1% of fruits infested is cause for concern.
Trunk banding
Applying trunk bands may be used for monitoring.
- Set a band of currugated cardboard covered with cling film on a sample of trees and count the number of cocooning larvae and pupae.