INDUCTION OF DORMANCY IN APHID PARASITOIDS - IMPLICATIONS FOR ENHANCING THEIR FIELD EFFECTIVENESS

The aphid parasitoid Pauesia unilachni Gahan entered diapause even und er short night conditions at 20 degrees C in oviparae of Schizolachnus pineti F. on Pinus sylvestris L., but Praon volucre Hal. did not unde r the same conditions in oviparae of Acyrthosiphon pisum Harris. Praon volucre or Aphidius matricariae Hal. reared in anholocyclic strains o f Aulacorthum solani Kalt., Aphis gossypii Glover and Myzus ascalonius Doncaster did not enter diapause under long night conditions at 15 de grees C. A cold shock could induce hibernal quiescence and diapause of Praon volucre in Acyrthosiphon pisum, but only hibernal quiescence oc curred in this parasitoid developing in anholocyclic hosts. These obse rvations show that environmental cues (temperature and photoperiod) as well as internal factors via host aphid such as host aphid life cycle , aphid morph and host plant quality are involved in the induction of dormant stages in aphid parasitoids. The importance of these findings is discussed in terms of enhancing parasitoid activity in the field.