Assessing augmentative releases of parasitoids using the «Recruitment method», with reference toEdovum puttleri, a parasitoid of the colorado potato beetle [Coleoptera: chrysomelidae]

Abstract

Release of approximately 17,700 experienced adult female Edovum puttleriGrissell against I st generation Colorado potato beetle eggs in 1987 in a 0.4 ha potato field in S. Deerfield, Massachusetts resulted in only 3.6 % parasitism as assessed by direct measurement of host and parasitoid recruitment. Levels of .non-viability indicated an additional 2.8 % of hosts killed by parasitoid hostfeeding, for an overall impact of 6.4 %. Release in 1988 of 126,300 parasitoid against 1 st generation hosts in a 0.4 ha potato (Solanum tuberosum L.) field at the same site produced only slightly higher levels of parasitism (10.6 %) and host feeding (2.0 %).Release in 1987 of 32,800 wasps against 2 na generation eggs resulted in only 0.7 % l~arasitism and 0.3 % host feeding due to the toxicity of fenvalerate (Pydrin ~) residues from a single application applied for control of the potato leafhopper, Empoascafabae (Harris). Release in 1988 of 47,400 wasps against the 2 "d host generation in the absence of any pesticide applications resulted in 34.4 % parasitism and 16.1% host feeding, for a total impact of 50.5 %. Difference in parasitization levels between host generations supports the idea that E. puttleri adults require an in-field carbohydrate source such as aphid honeydew to reproduce. In Massachusetts, aphid populations in potato typically do not develop until the end of the 1 St larval generation.The recruitment method of Van Driesche & Bellows (1988) proved to be a satisfactory approach for determining results of augmentative parasitoid releases.