Infectivity Of Oryctes Nudivirus Produced On Cell Culture DSIR HA-1179 Against Larvae And Its Effects On Feeding Of Neonates Of Rhinoceros Beetle, Oryctes Rhinoceros

Abstract

The Oryctes nudivirus (OrNV) is a classical biocontrol agent for a major oil palm insect pest the rhinoceros beetle, Oryctes rhinoceros. The infectivity of three Malaysian indigenous types of OrNV types A, B and C were tested on larvae and neonates. On larvae, the peroral inoculation test technique indicated that the highest mortality of 100% was achieved using type A produced from cell culture DSIR-HA-1179, while the highest infectivity of 41.7% was recorded for type A prepared from infected guts. No differences in infectivity were observed on other treatments, which ranged from 13.1% to 41.7%. In the substrate contamination inoculation test technique, results showed that the level of infectivity was even lower in all OrNV treatments, ranging as low as 6.7% to only 15.0%. Low infectivity was mainly due to inactivation of virus inocula in the larval food substrates. Based on the results for both inoculation methods, the OrNV type C prepared from cell culture DSIR-HA-1179 was found more effective in controlling the L3 larvae than the other types of OrNV. The impact of OrNV infection on food consumption by the neonates was studied. The feeding of inoculated neonates with OrNV reduced rapidly, especially at the early stage of the experiment between eight days after treatment (DAT) to 16 DAT. At this period, the food consumption by all tested OrNV was rapidly reduced and maintained low until the experiment ended at 60 DAT. The highest feeding reduction rate was on neonates treated by type A (-0.074x) followed by neonates treated by type C (-0.053x) and type B (-0.035x). Therefore, it was suggested that besides on highly virulent, the selection of OrNV for field release should also based on high reduction rate on food consumption by the infected insects on plant hosts.