THE INFLUENCE OF EGG PARASITOIDS BELONGING TO THE TELENOMUS-BUSSEOLAE(HYMENOPTERA, SCELIONIDAE) SPECIES COMPLEX ON SESAMIA-CALAMISTIS (LEPIDOPTERA, NOCTUIDAE) POPULATIONS IN MAIZE FIELDS IN SOUTHERN BENIN

During the second cropping season of 1992, maize fields in southern Be nin were examined twice at the pre-tasselling stage, to assess the abu ndance of eggs of Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and egg parasitism by Telenomus busseolae Gahan (Hymenoptera: Scelioni dae). They were also examined at harvest, to investigate the impact of egg parasitism early in the season on S. calamistis populations, and thus plant growth. S. calamistis eggs were found in 84.0% of the field s and on 16.8% of the plants. The parasitoid was present across the en tire survey area, with the rate of egg parasitism averaging 76.4%. On average, 84.1% of the egg masses/field were parasitized, indicating th at the parasitoid had a good capacity for searching. The relationship between parasitization rates and egg batch size was best described by a quadratic function, with maximum parasitism of about 95% between I a nd 25 eggs/batch. In a multiple regression analysis involving infestat ion levels at harvest, and soil and parasitoid variables, the T. busse olae parasitization rate was one of the major factors influencing S. c alamistis densities. The yield loss due to S. calamistis decreased wit h increasing egg parasitism.