Bio-efficacy of egg parasitoid, Trichogramma chilonis (Ishii) against spotted stemborer, Chilo partellus (Swinhoe) in Kharif maize

Abstract

Maize stem borer, Chilo partellus, is the most serious and ubiquitous pest of maize not only in India but also throughout the Asian countries where it is a constant threat. The larvae, after hatching, enter the plant whorl and feed inside the plant for rest of the life. Owing to its cryptic behavior, insecticides are not the right choice. Moreover, unwarranted use of pesticides has directly increased the cost of cultivation and accounted for many health as well as environmental hazards. Use of biological control agents is far better than harmful agro-chemicals in terms of health benefits and ecosystem stability, provided they are effective enough to suppress the pest population. Egg parasitoid, Trichogramma chilonis, has proven its worth against many lepidopteran borers and provided satisfactory control in many crops. With this view, an experiment was conducted to evaluate the potency of T. chilonis against spotted stem borer, Chilo partellus at laboratory and research area of CCS Haryana Agricultural University, Regional Research Station, Karnal during Kharif, 2017. In our study, maximum egg parasitization (62.40%) was recorded in treatment with two releases of T. chilonis parasitized eggs @ 1,25,000/ha at 7 and 14 days after germination (DAG) which was at par with two releases of T. chilonis parasitized eggs @ 1,00,000/ha at 7 and 14 DAG (60%) whereas treatment with one spray of Dimethoate 30 EC @ 660 ml/ha had minimal T. chilonis activity (3.5% parasitization). Lower leaf injury rating (LIR), plant infestation and dead hearts were recorded in treatments with two release of T. chilonis parasitized @ 1,25,000 and 1,00,000 eggs/ha at 7 and 14 DAG which were statistically comparable with Dimethoate 30 EC treated plots. Whereas treatments with single release of T. chilonis parasitized eggs did not provide satisfactory control. Treatment with two releases of T. chilonis parasitized eggs @ 1,00,000/ha at 7 and 14 DAG was the most economically remunerative with the highest incremental cost: benefit ratio (1:32.48) and benefit: cost ratio (1.41).  Although, pesticide treated plots (Dimethoate 30 EC @ 660 ml/ha at 7 DAG) provided satisfactory monetary return but it is not environmentally compatible and ecologically viable for long run.