Essential Oils as a Source of Ecofriendly Insecticides for Drosophila suzukii (Diptera: Drosophilidae) and Their Potential Non-Target Effects.

The spotted wing drosophila (Drosophila suzukii) is one of the main invasive pests of small fruits in the world. Thus, 19 essential oils (EOs) were selected to analyze the effects through toxicity and repellency on oviposition and D. suzukii adults. In addition, their lethal and sublethal effects on the pupal endoparasitoid Trichopria anastrephae were evaluated. The EOs of C. flexuosus and Mentha spp. had the highest toxicity observed in the topical application bioassay for D. suzukii. In contrast, the EOs of C. verum, C. citratus QT citratus, and C. winterianus showed the highest toxicity in the ingestion bioassay for D. suzukii. The dry residues of C. verum and C. citratus QT citratus reduced the oviposition of D. suzukii. In the repellency bioassays, the 19 EOs analyzed repelled ≅ 90% of the D. suzukii females. All EOs evaluated using the LC90 values of the products provided mortality of less than 20% of T. anastrephae adults and did not cause a reduction in the parasitism of surviving T. anastrephae females. We conclude that the EOs evaluated have the potential to be used in the management of D. suzukii. They can also serve as selective active ingredients for the formulation and synthesis of new biopesticides.

Essential Oil of Rosmarinus officinalis Ecotypes and Their Major Compounds: Insecticidal and Histological Assessment Against Drosophila suzukii and Their Impact on a Nontarget Parasitoid.

Essential oils (EOs) produced by plants in the Lamiaceae family may provide new insecticidal molecules. Novel control compounds are needed to control Drosophila suzukii (Matsumura), a severe economic invasive pest of thin-skinned fruit crops. Thus, we characterized the main compounds of EOs from three rosemary Rosmarinus officinalis ecotypes (ECOs) and evaluated their toxicity to D. suzukii adults, deterrence of oviposition behavior, and histological alterations in larvae. Additionally, we analyzed the lethal and sublethal effect on the pupal parasitoid Trichopria anastrephae. The main compounds identified in the R. officinalis ECOs were α-pinene, camphor and 1,8-cineole. In bioassays via topical application or ingestion, ECOs and their major compounds showed high toxicity on D. suzukii adults and a lower concentration could kill 50% and 90% of flies compared to spinetoram. The dry residues of a-pinene, 1,8-cineole, and camphor provided a repellent effect by reducing D. suzukii oviposition by ~47% compared to untreated fruit. Histological sections of 3rd instar larval D. suzukii posttreatment revealed damage to the fat body, Malpighian tubules, brain, salivary gland, and midgut, which contributed to high larval and pupal mortality. Survival and parasitism by adult T. anastrephae were not affected. Thus, R. officinalis EO and their compounds have potential for developing novel insecticides to manage D. suzukii.

Toxicity of Bacterial Isolates on Adults of Zaprionus indianus (Diptera: Drosophilidae) and Parasitoids Trichopria anastrephae (Hymenoptera: Diapriidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae).

Bacillus thuringiensis (Berliner) has demonstrated potential use in insect pest management. We evaluated the toxicity and sublethal effects of formulations of toxic baits composed of bacterial isolates (Bt) B. thuringiensis var. oswaldo cruzi (Bto), B. thuringiensis var. israelensis (Bti), B. thuringiensis var. kurstaki (Btk), and B. circulars (Bc) in combination with three food attractants 50% grape juice, 7% sugar cane molasses, and 7% hydrolyzed protein on adults of Zaprionus indianus (Gupta, 1970), the main pest of fig fruit (Ficus carica) in Brazil. Likewise, we evaluated the toxicity on the parasitoids Trichopria anastrephae Lima, 1940 and Pachycrepoideus vindemmiae (Rondani, 1875) in ingestion bioassays. Adults of Z. indianus showed high susceptibility to Bacterial isolates. However, the Bto isolate (1013 CFU. ml-1) caused adult mortality of 100%, in 72 h after exposure, with LT50 values of ≈20 h. By using the lethal concentrations (LC90) of the Bto isolate, estimated via the concentration-response curves with the food attractants, a significant reduction (40 to 50%) in the total fecundity and in the embryonic viability of eggs from females fed with the toxic baits was observed. The food attractants + Bto (80 × 108 CFU. ml-1) did not cause significant mortality of T. anastrephae and P. vindemmiae adults (mortality < 20%). The bacterial isolates Bti, Btk, Bc, and Bto are considered promising for the formulation of toxic baits, because, besides providing toxic effect on adults of Z. indianus, they showed no toxicity on T. anastrephae and P. vindemmiae adults.