Compatibility of Entomopathogenic Fungi with Neonicotinoids for the Management of Brown Plant Hopper of Rice, Nilaparvata lugens stal. (Delphacidae: Hemiptera)

Abstract

Background: Rice is the staple food of Indians and it is attacked by more than 100 species of insects. Among all, brown planthopper (BPH), Nilaparvata lugens (Stal) (Hemiptera: Delphacidae) is one of the major sucking insects, which can cause appreciable damage by sucking sap on other hand transmitting viral diseases. Farming community using several insecticides for managing the BPH. However, continuous use of these insecticides causes health hazards and environmental pollution and also leads to development of insecticide resistance. Keeping this view in mind, the present investigation has been planned with combined use of fungal formulations and commonly used neonicotinoid insecticides in rice eco system for managing BPH. Methods: This experiment was carried out in two parts, one is studied the compatibility between neonicotinoids (Thiamethoxam 25 SG and Dinotefuran 20 SG) and entomopathogenic fungi (Beauveria bassiana, Metarhizium anisopliae and Lecanicillium lecanii =Verticillium lecanii) by following the standard poison food technique. Second one is after studied the compatibility between neonicotinoids and entomopathogenic fungal agents, inhibitory studies were conducted under glasshouse conditions. Result: The study revealed that two tested insecticides affected the radial growth of fungi partially at all the three concentrations (0.5RC, RC and 1.5RC). At recommended concentration (RC), dinotefuran 20 SG @0.4 g/l was found to be slightly harmful to all three fungi (20% - 35% reduction of the growth of the fungus) and thiamethoxam 25 SG @ 0.25g/l appeared to be slightly harmful to B. bassiana and M. anisopliae and moderately harmful to L. lecanii (35-50% reduction of the growth of the fungus). Thiamethoxam 25SG alone recorded 65.0% mortality of BPH and when mixed with B. bassiana and M. anisopliae gave 86.25% and 81.25% mortality of BPH respectively under glass house conditions. Similarly, Dinotefuron 20 SG alone could gave 98.75% mortality of BPH.