Variasi Virulensi Strain-strain Beauveria bassiana (Bals.) Vuill. Terhadap Larva Plutella xylostella (L.) (Lepidoptera: Plutellidae)

摘要

The objective of this laboratory study was to screen for the three most virulent among 16 B. bassiana isolates against P. xylostella larvae. The tested isolates were originally obtained from several insects, i.e. Nilaparvata lugens, Plutella xylostella, Chrysodeixis chalcites, Hypothenemus hampei, Conopomorpha cramerella, Thrips tabaci, Leptocorixa acuta. The third instar of P. xylostella were inoculated by topical application of B. bassiana isolates. Conidia from slant culture of GYA added chitin from small mole criket diluted to get 103, 104, 105, and 106 conidia per ml. This bioassay was carried out to determine the median lethal concentration (LC50) and median lethal time (LT50) of the isolates. Isolates from N. lugens (WC), P. xylostella (PD1), and H. hampei (BBL) were the three most virulent with LC50 (15 hours after application) of 1.3 x 103, 8.3 x 103, and 6.8 x 103 conidia per ml, respectively. LT50 at 1 x 106 conidia per ml of WC, PD1, and BBL isolates were 6.0, 7.6, and 6.4 hours, respectively. At 1 x 106 conidia per ml, all isolates were able to kill larval and pupal stages.