Activation of gonads and disruption of imaginal diapause in the apple blossom weevil, Anthonomus pomorum (Coleoptera : Curculionidae), with juvenoidsin laboratory and field trials

A possibility of using synthetic analogues of juvenile hormone (juvenoids) to disrupt imaginal diapause of the apple blossom weevil, Anthonomus pomoru m females was demonstrated. Out of three preparations tested (methoprene, f enoxycarb and W-328) methoprene and fenoxycarb appeared to be effective. Se nsitivity to juvenile hormone analogues develops early after imaginal emerg ence (even before the female starts to feed) and lasts throughout the whole aestivo-hibernation dormancy. Although the juvenoids could stimulate the o nset of oogenesis at any time during diapause, the propensity of the ovarie s to form normal eggs developed only during hibernation part of the dormanc y; in earlier stages of diapause accumulation of yolk was observed but matu red eggs were not produced. Methoprene treatment caused marked increase of locomotory activity accompanied with decrease of dry weight, increase of wa ter content, depletion of trehalose resources, decrease of cold hardiness a nd, finally, 100% mortality within four weeks in the weevils treated during their feeding or aestivation stages. Although similar changes were observe d in the treated pre-feeding weevils, they later recovered and survived unt il next spring without apparent loss of cold hardiness. A possibility of de signing a control method based on this principle is discussed and the resul ts of small-scale field trials that support its plausibility are reported.