|
Abstract
|
Larvae of Potato tuber moth (PTM), Phthorimaea operculella (Zeller), attack foliage and tubers of potato (Solanum tuberosum L.) causing significant economic damage. Chemical-based control of PTM have shown limited efficacy. The PTM polyvolatility and adaptability towards the seasonal changes of the weather conditions and high ability of the species to develop resistance towards the traditional chemical insecticides belonged to organophosphorous, carbamate and pyrethroid make its control very difficult. The main objective of this study was to evaluate the virulence of an entomopathogenic nematode, Steinernema carpocapsae to developmental stages of PTM. Bioassay was conducted using different concentrations of infective juveniles of studied EPN including 1, 5, 10, 50 and 100 IJ(s)/Pre-pupa or pupa. The entire experiments replicated twice with three replications of each treatment. Mortality data was recorded from 2nd day after exposure to IJs up to 7th day. The effects of S. carpocapsae concentrations on PTM pre-pupa was significantly different (p≤0.05). Highest (94.44%) and lowest (0.00%) rates of pre-pupa mortality were recorded at 100 and 1 IJs/Pre-pupa, respectively. These values for pupa state were 44.28% and 2.37% which were recorded at same concentrations as pre-pupa. The results showed that both developmental stages of PTM are susceptible to S. carpocapsae but virulence on pupa was considerably lower than pupa. These results are in congruence with IJs host finding strategy. Infective juveniles of S. carpocapsae by having ambusher host finding strategy are not capable to seek sessile life stage of the host or conceal ones. Only active and mobile stages of the pest with are in danger of seeking by this species of EPN.
|