Boron compounds are effective on Sitophilus granarius (Coleoptera: Curculionidae) and Rhyzopertha dominica (Coleoptera: Bostrichidae)

Abstract

In the current study, the insecticidal efficacy of disodium octaborate tetrahydrate (Etidot-67), ammonium tetrafluoroborate (ATFB), sodium metaborate tetrahydrate (SMT), and calcium metaborate (CMB) was evaluated at doses of 500, 750, 1000, and 1250 ppm via diet delivery on Sitophilus granarius (Linnaeus, 1875) (Coleoptera: Curculionidae) and Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae) under laboratory conditions at 25 ± 1 °C, 60 ± 5% relative humidity, and continuous dark. Dead insects were recorded 5–21 days after application with three replications each repeated three different times. Etidot-67 showed complete mortality against S. granarius at 1000 ppm on the 17^th day, while CMB showed 99.9% mortality at 1250 ppm on the 21^st day. Rhyzopertha dominica was completely controlled with Etidot-67 treatment at 1250 ppm on the 21^st day, whereas CMB led to 93.7% mortality at a dose of 1000 ppm 21 days after treatment. ATFB and SMT showed no significant activity at any dose or time interval. The progeny production (F₁) was assessed following a 45-day exposure period. The highest F₁ suppression rate (92.8%) for S. granarius was detected from Etidot-67, while a complete suppression rate for R. dominica was detected from Etidot-67. The two most effective boron compounds, Etidot-67 and CMB led to reduced triglyceride levels and body weight loss in R. dominica. However, the reduction in the triglyceride levels and body weight loss in S. granarius by both compounds was obtained only via diet delivery; therefore, an anti-feeding effect is also possible. Finally, scanning electron microscopy showed smaller, indented, and relatively uniform particles for CMB, unlike the Etidot-67. Overall, Etidot-67 and CMB have promising potential in stored product pest management.