Natural Parasitism and Release Efficiency of Trichogramma evanescens Westwood in Ostrinia nubilalis Hübner Attacking Maize in Turkey

Abstract

The natural parasitism rate and the release efficiency of the egg parasitoid, Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae), in the biological control of the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae), was determined in field plots of maize in the Eastern Mediterranean, Turkey. Parasitoids were released in maize plots as parasitized eggs of laboratory-reared Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The parasitized eggs (n = 150,000) were released twice in a 10-d interval at the beginning of the oviposition period of the third generation of O. nubilalis in the second crop of maize in released treatment (without insecticides). Other treatments were an untreated control (without wasps and without insecticides) and an insecticide treatment (Lambda-Cyhalothrin, 50 g I−1 300 ml ha−1; without wasps). Ostrinia nubilalis egg masses, larvae and plant damage were regularly assessed until crop harvest. Parasitization of egg masses by T. evanescens was determined in each sample. The mean (± SD) percentage of parasitized O. nubilalis eggs was 86.2 ±l11.6 (± SD)%. Compared with the control treatment, the number of plants damaged by European corn borer larvae in the release treatment was reduced by 96%, whereas the number of larvae was reduced by 95.2%. Average grain yield was 8,800 ± 15.2 kg ha−1 (380.0 ± 1.6 g per 1000 grain weight) in the Trichogramma release treatment without insecticide, 7,000 ± 28.8 kg ha−1 (314.8 ± 2.9 g per 1000 grain weight) in the control treatment, and 8,533 ± 8.8 kg ha−1 (360.4 ± 8.5 g per 1000 grain weight) in the insecticide treatment. The grain yield and 1000 grain weight differences differed significantly (P ≤ 0.01) between the untreated control and the other two treatments (released treatment and insecticide treatment). Natural parasitization of O. nubilalis eggs by T. evanescens as observed in control and insecticide-treated plots was 30.2%. These results indicate that biological control of O. nubilalis with T. evanescens should be developed as an integral control method in integrated management programs for maize grown in Turkey.