INFLUENCE OF GRASS SPECIES ON THE FORAGING BEHAVIOUR OF PLATYGASTER HIEMALIS, A PARASITOID OF THE HESSIAN FLY, MAYETIOLA DESTRUCTOR

摘要

Platygaster hiemalis is an egg parasitoid of the Hessian fly, Mayetiola destructor, a pest of both New Zealand wheat, Triticum aestivum (Tribe Triticeae), and prairie grass, Bromus willdenowii (Tribe Bromeae). The searching and ovipostion behaviour ofP. hiemalis females in relation to Hessian fly eggs oviposited on these two grass hosts was investigated. Individual females (n=15) were observed foraging for 60 min in an array of six wheat seedlings and six prairie grass seedlings, with all plants bearing Hessian fly eggs (mean of 5-6 eggs), and plant type alternated within the array. Before being released into the array the female had oviposited but had not experienced either plant type as an adult. On average P. hiemalis females made 7.7 visits toplants during the 60 min observation period, with some of these being repeat visits to the same plant. Wheat plants were visited twice as frequently as prairie grass plants. Once on the plant, females on prairie grass plants were just as likely to find eggs as females on wheat plants. These results indicate that P. hiemalis is potentially as effective at parasitising Hessian fly in prairie grass pastures as in wheat fields.