OLFACTORY RESPONSE OF ANAGRUS-NIGRIVENTRIS (HYM, MYMARIDAE) - EFFECTSOF HOST-PLANT CHEMICAL CUES MEDIATED BY REARING AND OVIPOSITION EXPERIENCE

The egg parasitoid Anagrus nigriventris Girault is an important natura l enemy of the beet leafhopper, Circulifer tenellus (Baker) which has a broad host range that includes cultivated sugar beets and the weed, Russian thistle. When parasitoids were reared on leafhopper eggs depos ited in sugar beets, females were attracted to sugar beet volatiles an d preferred them over a blank control and over Russian thistle volatil es in Y-tube olfactometer tests. No preference was detected for either plant by female wasps that were reared on Russian thistle. Wasps rear ed on Russian thistle and allowed an oviposition experience on sugar b eet showed a strong attraction to sugar beet volatiles; however, wasps reared on sugar beets and allowed oviposition experience on Russian t histle demonstrated no preference between the two plants. The implicat ions of parasitoid response towards plant volatiles and their importan ce in biological control are discussed.