Apple blossom weevil: Offering alternative shelters (BIOFRUITNET Practice Abstract)

Summary in the original language of the document

Trapping and removing the weevils reduces the need to intervene with control agents and decreases damages.
Practical recommendations
Trapping is especially efficient in orchards with as few natural hiding places as possible, e.g., in young orchards. This practice is less effective in older orchards with many hiding places (rough trunk) and with hollow PVC tying tubes - when possible, remove the tubes.
Making the bundles
• Use PVC tying tube with an outer diameter of 4-5 mm.
• The standard shelter consists of a bundle of 10-20 pieces of tying tubes of 14-20 cm long, folded in half (20 cm) or straight (14 cm), tied together with a nylon cable tie. Including a Treefix elastic band allows for securing the bundles to the trunk. Preliminary results show that straight, non-folded bundles are effective as well. A larger number of tubes per bundle allows for a higher number of weevils hiding per bundle.
• Bundles can be made by hand. They are not yet commercially available.
• Make straight bundles: Put 20 rolls of tying tube on a horizontal pole. Sample all threads together. Cut at 14 cm. Fasten the tie-wrap (~12 cm all nylon) tightly around bundle, including a Treefix elastic band (11 cm).
• Install the bundles by end of May, when the young weevils have left the flowers.
• Attach the bundles tightly to the trunk at about 1 m height. Contact of the bundle shelters with the trunk is essential.
• Hang one bundle per tree. Research is ongoing to better understand the optimum bundle density.
Collecting the bundles
• Collect the bundles between December-January when it is cold, and the weevils are inactive.
• Put the bundles in a closed plastic bag, a closed box or other place from where they cannot escape. Packed bundles may be put in a cold storage.
• Inside the bags or boxes, the weevils will leave the bundles and die. In May, the bundles can be used again.
Monitoring apple blossom weevil: On a warm day in early spring, check for weevils by tapping branches above a collection sheet. Sample in the afternoon when the weevils are active. The threshold for apple blossom weevil is 5-10 weevils per 100 tapped branches. In a year with many flowers more weevils are tolerated than when flowering is poor.
Direct control measurements
• When necessary, use Pyrethrum early in the season on the adult weevils. Pyrethrum is a contact-insecticide and should be applied with a lot of water. Check the registration status for Pyrethrum in your country.