Figure 4.

Effect of PLA₂ inhibition induced by S. feltiae K1 infection on insecticidal activity against P. xylostella larvae. (A) Inhibition of PLA₂ activity in the plasma of P. xylostella larvae by the nematode infection (‘Challenged’) of S. feltiae K1. Hemolymph was collected every 4 h after the nematode infection to prepare plasma samples. Each treatment was replicated three times. (B) Influence of arachidonic acid (‘AA’, 10 μg/larva) or dexamethasone (‘DEX’, 10 μg/larva) addition on mortality of P. xylostella larvae infected with S. feltiae K1. Indicated concentrations of test chemicals were injected into hemocoel of test insects followed by nematode treatment (80 IJs/larva). Subsequent mortality was measured at 72 h after nematode treatment. Each treatment was replicated three times. For each replication, 10 larvae were used. Different letters above standard error bars indicate significant difference among means at Type I error = 0.05 (LSD test).