Effect of antipyretic phenidone on the nodulation response and mortality of locust infected with fungus

• Nodulation response in locusts decreased following injection with the antipyretic drug. • Phenidone increased mortality rate in infected locusts. • Phenidone reduced the therapeutic effect of thermoregulation on the survival of infected locusts. The use of eicosanoids biosynthesis inhibitors (EBIs) as immune disruptors in host-pathogen interaction is a promising tool in insect pest control. In this study, co-applying the dual cyclooxygenase (COX) and lipoxygenase (LOX) inhibitor phenidone (104 µg/larva) with the entomopathogen Beauveria bassiana (10 8 spores/mL) on Locusta migratoria manilensis , sharply declined the nodulation response. The reduction of nodulation response by phenidone proved that the dual COX/LOX is involved in nodules formation in L. migratoria manilensis . We investigated the effect of the antipyretic drug on the fungus virulence under different thermal conditions (thermoregulation and non-thermoregulation). Interestingly, a significant increase in the mortality rate of fungus-phenidone treated locusts was recorded. The drug suppressed the therapeutic effect of thermoregulation in infected locusts combined with phenidone tailoring a mortality rate of 70% by 14 days post-infection. Whereas 40% of the mortality rate was observed in those infected locusts under the same thermal condition but not treated with phenidone. These findings indicated that phenidone can cripple the immune defense of L. migratoria manilensis and additionally increase the virulence of B. bassiana under certain ecological conditions.