Laboratory and field evaluation of selected isolates of Metarhizium anisopliae and Beauveria bassiana against the leaf beetle Epilachna indica Mulsant
2008
Yusof Ibrahim | Tan, Gek Kiang | Cheong, Chee Kong, Putra Malaysia Univ. (UPM), 43400 UPM Serdang, Selangor (Malaysia). Faculty of Agriculture. Dept. of Plant Protection
Six isolates of selected entomopathogenic fungi were tested for their efficacy against the eggs, larvae and adults of the ladybird beetle, Epilachna indica (Mulsant), under an ambient environment of 28 ± 20C, 85 ± 15% RH and 12 h photoperiod. All Metarhizium anisopliae were isolates were infective against the eggs, larvae and adults of E. indica. Exposure to a suspension of 1 x 108 conidia ml-1 resulted in 99.2 - 91.5% infection on the eggs, 71.7 - 65.0% on the 1st instar larvae, and 86.7 - 76.7% on the adults seven days after treatment (7-DAT). Probit analysis showed significantly positive relationship between log dosage and probit mortality , values with isolate MaOr providing the best estimated median effective concentration (EC50) of 9.268 x 103 conidia ml-1 against the eggs, and 2.855 x 106 conidia ml-1 against the 1st instar larvae with estimated median lethal time (LT5o) value of 4.9 days, while isolate MaPs gave the best EC5o value of 1 .486 x 10 5 conidia ml-1 with LT5o pt value of 7.0 days against the adults. Infectivity by Beauveria bassiana was rather weak with the highest infection (54.5%) on the eggs being inflicted by isolate BbPc, while the highest against the 1 st instar larvae (58.3%) by isolate BbGc, and that against the adults (40.0%) by isolate BbPc. In general, isolates of M. anisopliae inflicted the highest mortality against the eggs, larvae and adults of E. indica. Field experiment showed M. anisopliae (MaPs) and Deltamethrin were equally effective and inflicted significantly higher larval mortality (75.0% and 98.0%, respectively) and lesser leaf damage (81.4% and 78.6%, respectively) compared to B. bassiana (BbGc) and the control five days after the last spray.
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