Differences in the searching behaviour of two strains of the egg parasitoid Telenomus busseolae (Hymenoptera: Scelionidae)

Stefano Colazza,M Cristiana Rosi

doi:10.14411/eje.2001.009

Abstract

Telenomus busseolae Gahan (Hymenoptera: Scelionidae) is an egg parasitoid, which is under evaluation for possible introduction into Italy as a biological control agent of the Corn Stalk Borer, Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae). Two strains are being considered, one from Africa and the other from Turkey. In a series of laboratory experiments we compared their reproductive capacities, walking behaviour, and host selection behaviour mediated by the sex pheromone and body scales of the host. As reciprocal crosses between the two strains yielded female offspring, they are not reproductively isolated. The two strains were similar in both their reproductive capacity and female longevity. Females of both produced 75-90 eggs and lived on average for 6-7 days. There were differences between the two strains in walking behaviour, searching pattern and in the host location behaviour. The African strain walked faster then the Turkish strain, and showed a slower angular speed and lower turning rate. The African strain showed a significant increase in its speed of movement in response to the host's sex pheromone and a more intense local search after encountering host body scales. These results on intraspecific variability could help choosing an appropriate strain of T. busseolae for corn borer management in Italy.

Highlights

The scelionid Telenomus busseolae Gahan is a solitary egg parasitoid of several species of noctuid stemborers (Alexandri & Tsitsipis, 1990; Setamou & Schulthess, 1995; Fantinou et al, 1998), and has been recorded from several African and Middle East countries and in India (Polaszek et al, 1993)
The Turkish strain was established from parasitised egg masses of S. nonagrioides collected from maize in the region of Adana, Turkey, and the African strain from about 18 parasitised egg masses of Sesamia calamistis Hampson collected from maize fields in southern Benin
T. busseolae adults of both strains were supplied with honey-water solution and S. nonagrioides egg-masses in glass tubes (16 ml)

Summary

Introduction

The scelionid Telenomus busseolae Gahan is a solitary egg parasitoid of several species of noctuid stemborers (Alexandri & Tsitsipis, 1990; Setamou & Schulthess, 1995; Fantinou et al, 1998), and has been recorded from several African and Middle East countries and in India (Polaszek et al, 1993). In Italy, S. nonagrioides is a pest of cultivated Graminaceae (Prota, 1965; Nucifora, 1966), and newly emerged larvae are controlled mainly with chemicals. These chemicals are used in conjunction with female sex phero mone traps (Rotundo et al, 1985). In 1995 and 1996, respectively, specimens from Adana (Turkey) and Cotonou (Republic of Benin), were reared in isolation and identified as a separate strain sensu Diehl & Bush (1984)

Methods

Results

Conclusion