Application Of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) And Bacillus Thuringiensis For Controlling The European Corn Borer Ostrinia Nubilalis Hübner (Lepidoptera: Pyralidae) In Maize Fields

• Mona B. El Mandarawy, Saadia A. Abdel Samae and Moustafa A. El Naggar
• Plant Protection Research Institute, A.R.C., Dokki, Giza, Egypt.

Abstract

Experiments were conducted, at Sakha, Kafr El-Sheihk Governorate for three seasons 2001, 2002 and 2003. Bacillus thuringiensis (B.t.) applications targeted the larvae escaped from the parasitism with Trichogramma evanescens West. during the egg stage. Effect of B.t. on different developmental stages of the egg parasitoid T. evanescens inside the host eggs was tested under laboratory conditions. A slight reduction occurred among the adult parasitoid emergence. Also, the parasitoid females resulted from treatments were not affected, particularly, the ovipositional process. Based on the three season’s data, the mean natural parasitization rates on Ostrinia nubilalis Hübner eggs by Trichogramma in the experimental area were 38.37, 36.00 and 36.82% for 2001, 2002 and 2003, respectively. After two releases with a total of 96000 parasitoids/feddan, the mean rates of parasitization reached 74.72, 76.83 and 77.23% in the plots treated with parasitoid alone and 72.90, 74.21 and 75.56% in the plots treated with Trichogramma plus B.t., respectively. Reduction percentage in the population of O. nubilalis reached 51.79 and 73.21% in 2001 compared with 52.38 and 73.81% in 2002 and 56.00 and 76.00% in 2003, in the parasitoid plots alone and those combined with B.t. Also, the percentage of infested nodes and average numbers of holes, ears and tassels in the plots treated with Trichogramma combined with B.t. decreased significantly as compared to the control.