Adults
The normal method of determining the risk of damaging infestation by apple blossom weevil is to assess populations of adults shortly after emergence at bud-burst in March using the beating method.
- For each beat sample, a branch is tapped sharply with a beater (a 0.25 m length of stiff hose to prevent damage to the branch) over a 0.25 m2 collection tray.
- At least 25 (preferably 50) beat samples should be taken per orchard and the total number of weevils collected should be recorded.
- The economic threshold is taken to be 5 weevils in a 50 beat sample, but this may be too high when the quantity of blossom present is light.
Capped blossoms
Once capped blossoms are visible, the damage is done and it is too late to control the pest with insecticides to prevent damage in the current year.
- However, a watchful eye for capped blossoms should be maintained, especially at the edges of orchards next to woodland or near unsprayed apple trees.
- The pest is absent from most commercial orchards sprayed with conventional insecticides and the appearance of capped blossoms will be the first indications that the pest is starting to establish.
- The presence of damage one season should prompt detailed assessment of the pest in subsequent seasons.
Damage to fruits during the growing season, at harvest or during grading
- If significant malformation damage to fruits is seen one season, treatment is likely to be justified the next season to avoid damage intensifying.