Department of Plant Protection, Urmia Universiy, Urmia, Islamic Republic of Iran.
Abstract: (7527 Views)
The population response of Heliothis armigera larvae to nuclear polyhedrosis virus
(NPV) was investigated. The virus was introduced by permitting the larvae to feed on lettuce
leaves. Median lethal doses (LD50) were determined. The estimated LD50 values for
the first, second, third, early, and late fourth larval instars were 5, 141, 1226, 5168 and
24553 polyhedra per larva respectively. In the fifth larval instar a degree of maturation
resistance against virus infection was observed. An inverse relationship between mortality
and larval weight was detected. Expressing the results in terms of LD50 / mg of the larval
weight eliminated the observed variation in the susceptibility of larvae. The estimated
LD50 values for each of the larval instar groups were used to predict the response of the
larval population to virus infection. This procedure provided a sound determination of
the response pattern, from which 96% of the variation in the larval susceptibility could be
described in terms of the log larval weight.
Received: 2010/05/15 | Accepted: 2010/05/15 | Published: 2010/05/15