Feeding or Starvation: Which Condition Makes the Red Palm Weevil, Rhynchophorus ferrugineus Olivier, More Susceptible to Insecticides?

Nagdy F Abdel-Baky^1,2*Saleh S. Alhewairini^2*Saleem A. Alsalhee²Turki S. M. Alanazi²Raid R. Alharbi²

• ¹Department of Plant Protection, College of Agriculture and Foods, Qassim University, P.O. Box 6622, Buraidah 51452, Saudi Arabia, Department of Food Science and Human Nutrition, College of Agriculture and Veterinary Medicine, Qassim University, buraydah, Saudi Arabia
• ²Qassim University, Buraydah, Saudi Arabia

Over the last four decades, the red palm weevil (RPW), Rhynchophorus ferrugineus, has evolved from a regional threat into one of the world’s most devastating pests of date and ornamental palms, driving major economic losses as its hidden larvae silently destroy internal trunk tissues. Despite insecticides being the core tool in most control programs, it remains inconsistent and strongly influenced by R. ferrugineus physiological condition. The susceptibility of R. ferrugineus to chemical treatments depends greatly on its nutritional condition, whether feeding or starving, making this factor is a key element in optimizing IPM strategies. This study assessed how nutritional status, feeding versus starvation, shapes the sensitivity of R. ferrugineus larvae and adults to ten commonly used insecticides under three dose levels (½×, 1×, and 2× of the recommended rate). The results were clear, which indicate that starvation case sharply increased mortality, especially in larvae, which were consistently more vulnerable than adults. Voliam Flexi produced complete mortality under both conditions; however, other compounds such as Coragen, Cyprone, and Indocarb only achieved full larval mortality under starvation at the highest dose. In adults, 100% mortality with Medprid, Sivanto, Fiprol, and Deciban was observed only when insects were unfed (starved). Feeding reduced insecticide toxicity, likely by enhancing detoxification or diluting toxins through ingested sap, as seen in the LC₅₀ declines of Sivanto, Coragen, Fedothrin, and Lamdoc. Unfed insects were significantly more susceptible, highlighting feeding status as a key determinant of chemical efficacy. Overall, these findings highlight feeding status as a critical driver of chemical performance. Unfed RPW are significantly more susceptible, while feeding conditions noticeably dampen insecticidal action. Recognizing the connection between nutrition and chemical sensitivity offers a path toward smarter, more sustainable pest control. This study reveals that the feeding state of R. ferrugineus directly shapes its detoxification capacity, starvation weakens energy-driven defense pathways, allowing insecticides to persist longer and act more powerfully. These findings introduce a novel RPW control strategy, showing that insecticide treatment doses with natural food scarcity or brief pre-treatment starvation can boost efficacy, reduce chemical use, and sharpen IPM precision.