author(s)
Rudra N Borkakati, DK Saikia, Gaurav Kashyap and Bijan C Dutta

abstract
An experiment was carried out at Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat during 2014-15 and 2015-16. Potato variety “Kufri Megha” was raised in 18 m² plot containing 9 treatments including control and was replicated 4 times. The treatments were Metarhizium anisopliae (AAU strain, Biometa) 15 kg/ha; Beauveria bassiana (AAU strain, Biosona) 15kg /ha; Imidacloprid 20 g a.i./ha as soil drenching; Malathion 5% dust 40kg/ha as soil application; Metarhizium anisopliae (Ma4-NBAII strain)15 kg /ha; Metarhizium anisopliae (Ma35-NBAII strain) 15kg /ha; Beauveria bassiana (Bb5a-NBAII strain) 15 kg /ha; Beauveria bassiana (Bb23-NBAII strain) 15 kg /ha, along with imidacloprid 17.8 SL @ 20 g. a.i. /ha (0.4 ml/l) and Malathion 5% dust 40kg/ha taken as standard check and Untreated control against subterranean pests of Potato. Among the various treatments evaluated against potato, imidacloprid was the most effective and proved to be the best in reducing the population of red ant (Dorylus orientalis) with 10.25% during both the years 2014-15 and 2015-16. Amongst, biopesticides M.anisopliae(Ma-35), M.anisopliae(Ma-4) and B.bassiana(Bb-23) were very much effective after imidacloprid and Malathion. An average yield of 76.87 & 80.75, 78.02 & 78.75 and 78.75 & 79.00 q/ha were recorded in the M.anisopliae(Ma-35), M.anisopliae(Ma-4) and B.bassiana(Bb-23) treated plot during 2014-15 and 2015-16, respectively. Regarding, yield increase over control 14.145 & 50.93%, 20.60% & 47.19% and 16.19% & 47.67% yield increase over control were recorded in M.anisopliae(Ma-35), M.anisopliae(Ma-4) and B.bassiana(Bb-23) treated plot during 2014-15 and 2015-16, respectively.