PREDATION OF LEPTINOTARSA-DECEMLINEATA (COLEOPTERA, CHRYSOMELIDAE) BY COLEOMEGILLA-MACULATA (COLEOPTERA, COCCINELLIDAE) - COMPARATIVE EFFECTIVENESS OF PREDATOR DEVELOPMENTAL STAGES AND EFFECT OF TEMPERATURE

Laboratory experiments were conducted to evaluate the voracity of adult and larval stages of the polyphagous predator Coleomegilla maculata DeGeer on the Colorado potato beetle, Leptinotarsa decemlineata (Say), immature stages. After a period of 24 h at 25 degrees C in 50-mm petri dishes, adult coccinellids attacked 11 eggs and killed 14 first instars and 4 second instars. Fourth-instar coccinellids attacked 9 eggs and killed 11 first instars and 3 second instars. Effect of temperature on predation effectiveness of C. maculata adults, third and fourth instars was studied on potato stems infested with L. decemlineata eggs, first or second instars. No predation activity occurred at 7.5 degrees C. Predator effectiveness increased linearly with temperature in the subsequent 10-30 degrees C temperature range studied. At each temperature, no significant difference in the number of prey killed was observed between C. maculata adults and fourth instars. The use of potato stems in assessing predation by C. maculata significantly reduced the number of prey killed by introducing the need for searching by the predator. Results suggest that inundative releases of third-instar C. maculata against eggs and first instars of Colorado potato beetles could be of interest in the case where releases of adult coccinellids would fail because of their tendency to rapidly fly out of the field.