Key Points
• This FAR Arable Extra has been written based primarily on our knowledge of clover root weevil in pastoral scenarios.
• Clover root weevil (CRW) is a severe pest of mature white clover; the adults attack the foliage but larval feeding on the root system does the most significant damage.
• Adult feeding can kill a large proportion of emerging white clover seedlings in newly-sown crops.
• The larvae are creamy white, legless and can be found around the root system. Larval populations peak in late spring and again in autumn.
• CRW adults are very mobile, being strong fliers with flights occurring December-March. They are also very good hitchhikers.
• CRW adults are found almost all year round. Egg laying takes place December to November including over the winter.
• A parasitic wasp has been released that attacks the adult CRW.
• Application of a foliar insecticide during white clover establishment can be used to provide temporary control of adult CRW.
• Seed coatings do not provide adequate protection against this pest and should not be relied on.
• The use of insecticides can disrupt the biological control agent of CRW but it will eventually re-establish to attack adult CRW.
• FAR has initiated a small programme of research to examine how this pest would affect white clover seed crops and if it does what control measures can be put in place.