Abstract
Spodoptera litura
(Fabricius) is an agriculturally significant polyphagous insect pest that has evolved a high level of resistance to conventional insecticides. A dietary assay was used in this work to assess the resilience of field populations of
S. litura
to λ-cyhalothrin. Analysis of the function and expression of the cytochrome P450 gene was used to test the sensitivity of
S. litura
larvae to sub-lethal concentrations of the insecticidal plant chemical Precocene 1, both by itself and in combination with λ-cyhalothrin. The activity of esterase enzymes (α and β) was found to decrease 48 h post treatment with Precocene 1. The activity of GST enzyme and cytochrome P450 increased with Precocene 1 treatment post 48 h, however. Expression studies revealed the modulation by Precocene 1 of cytochrome P450 genes,
CYP4M16
,
CYP4M15
,
CYP4S8V4
,
CYP4G31
, and
CYP4L10
. While
CYP4M16
expression was stimulated the most by the synergistic Precocene 1 + λ–cyhalothrin treatment, expression of
CYP4G31
was the most down-regulated by Precocene 1 exposure. Hence, it is evident that λ–cyhalothrin-resistant pest populations are still sensitive to Precocene 1 at a sublethal concentration that is nevertheless capable of hindering their development. Precocene 1 can therefore be considered a potent candidate for the effective management of insecticide-resilient
S. litura
.