Risk and Toxicity Assessment of a Potential Natural Insecticide, Methyl Benzoate, in Honey Bees (Apis mellifera L.)

Evaluation of a Push-Pull Strategy for Spotted-Wing Drosophila Management in Highbush Blueberry

We evaluated a novel push-pull control strategy for protecting highbush blueberry, Vaccinium corymbosum, against spotted-wing drosophila (SWD), Drosophila suzukii. Methyl benzoate (MB) was used as the pushing agent and a previously tested SWD attractive blend of lure-scents was used as the pulling agent. MB dispensers (push) were hung in the canopy and lure-scent dispensers (pull) were hung in yellow jacket traps filled with soapy water around the blueberry bushes. Blueberries were sampled weekly, and any infestation was inspected by examining the breathing tubes of SWD eggs which protrude through the skin of infested fruit. The frequency of infestation, i.e., the proportion of berries infested with at least one egg, and the extent of infestation, i.e., the mean number of eggs in infested berries, were significantly reduced in treatments receiving MB dispensers as a pushing agent when infestation rates were very high. However, the mass trapping devices as a pulling agent did not provide comparable protection on their own and did not produce additive protection when used in combination with the MB dispensers in push-pull trials. We conclude that MB has the potential to be implemented as a spatial repellent/oviposition deterrent to reduce SWD damage in blueberry under field conditions and does not require the SWD attractant as a pulling agent to achieve crop protection.

Evaluation of Lethal and Sublethal Effects of Methyl Benzoate on the Generalist Predator Orius laevigatus (Fieber)

Methyl benzoate (MBe), a volatile organic molecule, has been shown to have insecticidal effects on a variety of agricultural, stored products, and urban arthropod pests in recent investigations. However, the toxicity of MBe against nontarget organisms has rarely been investigated. This study investigated the lethal and sublethal effects of MBe on the generalist predator Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) via different exposure routes. This species is an important natural enemy of thrips, aphids, and mites in biological control programs globally. Acute toxicity bioassays conducted on O. laevigatus showed that the lethal median concentration (LC50) values of MBe for topical and residual toxicity were 0.73 and 0.94%, respectively, after 24 hr of exposure. Importantly, a sublethal concentration of MBe (LC30 = 0.51%) did not affect the survival and reproduction of O. laevigatus. In addition, prey consumption by O. laevigatus under different exposure conditions with varying densities of Aphis gossypii (Glover) (Hemiptera: Aphididae) adults demonstrated a good fit for a Type II functional response. The sublethal concentration of MBe did not affect the attack rate and handling time of O. laevigatus compared to untreated insects, nor did it affect the longevity and fecundity of O. laevigatus females. Thus, according to the International Organization for Biological Control, the sublethal MBe concentration for O. laevigatus is categorized as harmless and may be used in conjunction with this predator species for integrated control of many agricultural insect pests.

Plant volatile compound methyl benzoate is highly effective against Spodoptera frugiperda and safe to non-target organisms as an eco-friendly botanical-insecticide

Recent studies have indicated that the plant volatile methyl benzoate (MB) exhibits significant insecticidal bioactivity against several common insects. However, the potential environmental hazards of MB and its safety to non-target organisms is poorly understood. In the present study, these characteristics were investigated through laboratory experiments and field investigations. The results revealed that MB was highly toxic to the agricultural pest, fall armyworm Spodoptera frugiperda. Compared with the commercial pesticide lambda-cyhalothrin, the toxicities of MB against S. frugiperda larvae and adults were comparable and 3.41 times higher, respectively. Behavioral bioassays showed that the percentage repellency of MB to S. frugiperda larvae was 56.72 %, and MB induced 69.40 % oviposition deterrence rate in S. frugiperda female adults. Furthermore, in terms of median lethal concentration (LC₅₀) and median lethal doses (LD₅₀), MB exhibited non-toxic effects on non-target animals with 3-d LC₅₀ of > 1 % to natural predators (Coccinella septempunctata and Harmonia axyridis), 3-d LD₅₀ of 467.86 µg/bee to the bumblebee Bombus terrestris, 14-d LC₅₀ of 971.09 mg/kg to the earthworm Eisenia fetida, and 4-d LC₅₀ of 47.30 mg/L to the zebrafish Brachydanio rerio. The accumulation of MB in the soil and earthworms was found to be extremely limited. Our comparative study clearly demonstrated that MB is effective as a selective botanical pesticide against S. frugiperda and it is safe to use in the tested environment, with no toxic effects on non-target animals and natural predators.

Larvicidal Activity of Methyl Benzoate, a Volatile Organic Compound, Against the Mosquitoes Aedes albopictus and Culex pipiens (Diptera: Culicidae)

Methyl benzoate (MBe) is a volatile organic molecule found in various plants; it is used as an insect semiochemical. MBe also has a biorational insecticidal effect against various agricultural and urban arthropod pests. The present study was the first to assess the larvicidal potential of MBe against fourth-instar larvae of the mosquitoes Aedes albopictus (Skuse) and Culex pipiens (L.). A positive association was observed between MBe concentrations and larval mortality in both the species. The highest mortality recorded was 100% for Ae. albopictus and 56% for Cx. pipiens after 24 h of exposure to 200 ppm MBe. The lethal median concentration (LC50) values of MBe against fourth-instar larvae of Ae. albopictus and Cx. pipiens were 61 ppm and 185 ppm, respectively. These results suggest that MBe has great potential for use as an environmentally friendly larvicidal agent for mosquito control.

Possible interference of Bacillus thuringiensis in the survival and behavior of Africanized honey bees (Apis mellifera)

Bacillus thuringiensis (Bt), an entomopathogenic bacterium, has been used as bioinsecticides for insect pest control worldwide. Consequently, the objective of this work was to evaluate the possible effects of commercial formulations of Bt products, Dipel and Xentari, on the survival and behavior of Africanized honey bees (Apis mellifera). Bioassays were performed on foragers and newly emerged (24-h-old) bees that received the products mixed in the food. Their survival and behavior were evaluated through the vertical displacement tests and the walk test, analyzed using software Bee-Move. Then, histological analysis of the mesenterium was performed. As control treatment was used sterile water. The honey bees' survival was evaluated for between 1 and 144 h. No interference of B. thuringiensis, Dipel and Xentari, in the survival of Africanized honey bees were found. Only Xentari interfered with vertical displacement behavior of newly emerged (24-h-old) bees. Both the products tested were selective and safe for A. mellifera.