Control of Cacopsylla (Psylla) pyri (L.) (Stenorhyncha, Psyllidae) by juvenile hormone analogues

Juvenoids could be a useful tool for the control of psyllids. The 12 new juvenoids synthetized at the Institute of Organic Chemistry and Biochemistry in Prague were tested by dipping the feeding plants in the juvenoid solution and by indirect contact application on Cacopsylla (Psylla) pyri (L.). The tested compounds were mostly less active than the commercial juvenoid, methoprene. However, even the low doses of active juvenoids which evoked only small malformations on wings and external genitalia of the treated psyllids disabled them from flying and also from copulation. The most sensitive period for juvenoids in psyllids comprises the first 4 days of the last larval instar. Aside from this period, juvenoids failed to evoke any malformation. The investigated juvenoids were also tested on the main predator of psyllids, the pirate bug, Anthocoris nemoralis (Fabr.), using the indirect topical application. It was found that the sensitive period of these bugs to the tested juvenoids is restricted to the first 24 h of the last larval instar. Hence, the pirate bug revealed very low sensitivity to the tested juvenoids.