Efficacy of Entomopathogenic Fungi against Red Tef Worm, Mentaxya Ignicollis (Walker) (Lepdoptera: Noctuidae)

Abstract

Red tef worm (M. ignicollis) is a serious pest of tef (Eragrostics tef (Zucc.), Trotter: Poaceae) grown on black soils. Hence the present study was conducted to identify the effective isolate and conidial concentration of the entomopathogenic fungi (Beauveria bassiana and Metarhizium anisopliea isolates) and to measure the larval mortality of M. ignicollis caused by the entomopathogenic fungi and, thereby controlling RTW to increase the production of tef on black soils. Laboratory studies were carried out in completely randomized design of with four fungal isolates at four conidial concentrations against 3rd instar larvae of red tef worm. The green house study were carried out in randomized complete block design with the four isolates at the concentration of 1x109 spores/ml. Percent mortality increased from 46.67 to 83.33% and 43.33 to 73.33% when larvae were treated with M. anisopliae isolate, MM and PPRC-2, respectively, whereas, B. bassiana isolates PPRC-56 and PPRC-9609 caused mortality ranging from 43.33 to 66.67% and 43.33 to 50%, respectively when applied at the conidial concentration of 1x106 to 1x109spores/ml under laboratory condition. Percent mortality under greenhouse condition showed that MM (70%) was the most virulent isolate; however, PPRC-2, PPRC-56 and PPRC-9609 caused larval mortality of 60%, 53.33% and 46.67% respectively. It was concluded that all tested isolates can cause infection on 3rd instar larvae of red tef worm and able to cause delayed effect to the next stages after application; however, in both laboratory and greenhouse studies, isolate MM was the most effective at conidial concentration of 1x109 spores/ml. In general, MM (1x109spores/ml) isolate was found to be effective and potency against 3rd instar larvae of red tef worm under laboratory and greenhouse conditions. Therefore, since this agent is safe to the environment and other beneficial organisms and it is recommended to be verified for usage under open and large field conditions for the control of red tef worm.