Laboratory and Field Evaluations of Beauveria bassiana (Bals.-Criv.) Vuill. and Metarhizium robertsii (J. F. Bisch, Rehner & Humber) Against the Brown Plant Hopper, Nilaparvata lugens Stal and Its Natural Enemies in Paddy Fields in Thailand

Fourteen entomopathogenic fungi were tested for controlling females of the brown plant hoppers; Nilaparvata lugens Stal, Sogatella furcifera Horvath, Nephotettix virescense Distant, and Recilia dorsalis Motschulsky under laboratory conditions. The two most virulent fungi, Beauveria bassiana CKB- 048, and Metarhizium robertsii CKM-048 showed good capabilities in controlling N. lugens and S. furcifera. None of them could control N. virescense and R. dorsalis effectively. B. bassiana CKB-048 and M. robertsii CKM-048 were formulated into wettable powder form using dextrose anhydrous as filler and then tested at 2 paddy fields in Thailand for controlling N. lugens. The chemical (isoprocarb) was used for comparison. Efficacy of both biocontrol agents against N. lugens was good but a bit inferior to the chemical control treatment. However, the effect of both biocontrol agents and the chemical against 3 natural enemies, Lycosa pseudoannulata Bosenberg et Stand, Tetragnatha maxillosa Thorell and Cyrtorhinus lividipennis Reuter were monitored. Statistically, there was no difference in population density among treatments for every natural enemy. Neither the biocontrol agents nor the isoprocarb had direct detrimental effect on the three natural enemies in paddy fields.