Natural Mycosis of Rice Brown Plant Hopper (Nilaparvata lugens Stål) in Eastern India

Abstract

The studies on natural mycosis of brown planthopper(BPH) in rice ecosystem of Eastern India found that Aspergillus flavus Linkk. caused maximum mortality (20 to 30%) followed by  Aspergillus niger (Teig.) (15 to 20%), Rhizopus sp. (10-20%)and Fusarium sp. (5-20%)  .  In some cases more than one fungus was found to colonise the dead insect viz. (Rhizopus + Trichoderma) - 5 to 15%, [Aspegillus flavus Linkk. + Trichoderma sp.] – 10%, [Fusarium sp. + Trichoderma sp. + Aspergillus flavus Linkk.]-5 to 10%.  Most of the fungi infected the insect solely but only  the Trichoderma sp was not found as sole coloniser of the BPH. The data  also showed that natural mycosis were most effective in I and II instars (0-25% BPH colonised) followed by III instar (0 to 20% BPH colonised), Vth instar (10 to 15% BPH colonised), IV instar (0 to 15% BPH colonised) and winged adult (5 to 10% BPH colonised).  Association of multiple fungus species with the dead insect was low in early stages (I, II and III instar) rather than IV, V and adult.  Generally incidence of Aspergillus flavus Linkk  on BPH appeared during the second week of September to third week of November with two distinct peaks on 3^rd week of September and 4^th week of October respectively. The correlation studies in 2 different agro- climatic zones showed that the BPH population had a significantly negative correlation with the percent infection by fungi. .  The effect  of different formulations of this natural Mycosis in laboratory showed that % mortality was highest (16%) in Talk based followed by wettable  powder of China clay (10.60%) and were significantly higher than water suspension (8.05%).  The interaction between two factors i.e. spore (A) x base (B) was also statistically significant.