Impact of a Turkish isolate and a plaque‐purified variant of SpliNPV‐B on larval stage development of Spodoptera littoralis (Lepidoptera: Noctuidae) Boisd

Abstract

Baculoviruses can alter the development and physiological status of their insect hosts. In the present study, two Spodoptera littoralis nucleopolyhedroviruses (SpliNPV-TR1 and SpliNPV-M2) were examined in terms of their effect on the stage development of S. littoralis at two doses/concentrations by inoculation of neonates or third instars. Both isolates had an acute pathological effect on neonates. However, larval development was prolonged (6-36 h) by either infection when neonates were infected. When third-instar larvae were inoculated, no mortality occurred until insects moulted to later stages. When the isolates were compared, more mortality occurred in the fifth instar with SpliNPV-M2 than with SpliNPV-TR1, whereas less mortality occurred in the sixth instar with SpliNPV-M2 than with SpliNPV-TR1. However, none of the isolates demonstrated a dose effect. Larvae died at 108-198 h post-inoculation at all infections, and none of them pupated. Larval development was retarded (0-126 h) for each stage when third-instar larvae were inoculated. Consequently, SpliNPV-M2 would be a more effective control agent than SpliNPV-TR1 for control of S. littoralis since it kills larvae at earlier developmental stages.

Comparative efficacy of two bio-insecticides in the fight against Helicoverpa armigera (Hubner, 1808) (Lepidoptera: Noctuidae) pest of crops

“…The results on HearNPV formulation toxicity and neem oil in terms of lethal time (TL50) (Table 4) revealed that HearNPV recorded a relatively shorter lethal time of 10 days 17 hours compared to neem oil, which recorded a 12-day 2-hour TL50. and Kalaivani, 2006) but also Insect resistance to synthetic insecticides (Ahmad et al, 2003;2007) and development of awareness of their detrimental effects has prompted the introduction of integrated pest management programs (Nathan and Kalaivani, 2006) for the control of these pests. It is in this context that a laboratory study was carried out with the aim of testing the biological effectiveness of a formulation based on Helicoverpa armigera Nucleopolyhedrovirus (HearNPV).…”

“…Although this assumption should be verified by field studies, it is likely that an average lethal time of more than seven days is too long to be very useful in preventing economic losses on most crops. Inefficiency in achieving rapid reduction in pest populations is one of the main drawbacks of baculoviruses and one of the reasons why farmers are often opposed to the use of these control agents (Toprak et al, 2007).…”

Diversity and biological activity of nucleopolyhedroviruses of the leafworm Spodoptera litura

“…The genotypes within an isolate can be separated by end-point cloning in vivo (Makela et al, 2010) or by plaque purification in cell culture (Stiles and Himmerich, 1998;Toprak et al, 2007). Co-occlusion of genotypically distinct virions in OBs is an adaptive mechanism that favors the maintenance of virus diversity during insect-to-insect transmission (Clavijo et al, 2010).…”