Physicochemical Characteristics and Superficial Damage Modulate Persimmon Infestation by Drosophila suzukii (Diptera: Drosophilidae) and Zaprionus indianus

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.

Susceptibility of Brazilian Populations of Anastrepha fraterculus, Ceratitis capitata (Diptera: Tephritidae), and Drosophila suzukii (Diptera: Drosophilidae) to Selected Insecticides

Anastrepha fraterculus (Wiedemann), Ceratitis capitata (Wiedemann), and Drosophila suzukii (Matsumura) are the main fruit pests in Brazil. Here, we evaluated the susceptibility of Brazilian populations of A. fraterculus, C. capitata, and D. suzukii to selected insecticides. In ingestion bioassays, adults from a laboratory susceptible population of each species were exposed to five different modes of action of insecticide. Then, field populations of each species were exposed to the diagnostic concentrations to evaluate possible changes in susceptibility. Our findings indicate that lambda-cyhalothrin, malathion, and spinosad had similar levels of toxicity against a susceptible laboratory population of A. fraterculus, with LC50 values of 6.34, 6.54, and 8.76 µg a.i./ml, respectively. Ceratitis capitata had similar susceptibilities to spinosad (1.30 µg a.i./ml), spinetoram (2.76 µg a.i./ml), and malathion (7.10 µg a.i./ml), but a lower susceptibility to lambda-cyhalothrin (76.55 µg a.i./ml). For D. suzukii, the LC50 values of deltamethrin (0.67 µg a.i./ml), malathion (3.30 µg a.i./mL), spinosad (4.16 µg a.i./ml), and spinetoram (4.75 µg a.i./ml) were lower than for abamectin (15.02 µg a.i./ml), acetamiprid (39.38 a.i./ml), and thiamethoxam (70.15 µg a.i./ml). The diagnostic concentrations, based on LC99 values of the insecticides, caused more than 99% mortality for most field populations of each species. For lambda-cyhalothrin the populations RS-1 (A. fraterculus) and SC (C. capitata) showed approximately 10% of live insects. These differences represent the natural variation in population susceptibility and not due to insecticide selection pressure. The diagnostic concentrations defined here should be used in future resistance monitoring programs in Brazil.

Insecticidal and oviposition deterrent effects of essential oils of Baccharis spp. and histological assessment against Drosophila suzukii (Diptera: Drosophilidae)

The diverse flora of the Atlantic Forest is fertile ground for discovering new chemical structures with insecticidal activity. The presence of species belonging to the genus Baccharis is of particular interest, as these species have shown promise in pest management applications. The objective of this study is to chemically identify the constituents expressed in the leaves of seven species of Baccharis (B. anomala DC., B. calvescens DC., B. mesoneura DC., B. milleflora DC., B. oblongifolia Pers., B. trimera (Less) DC. and B. uncinella DC.) and to evaluate the toxicological and morphological effects caused by essential oils (EOs) on the larvae and adults of Drosophila suzukii (Diptera: Drosophilidae). Chemical analysis using gas chromatography-mass spectrometry (GC-MS) indicated that limonene was the main common constituent in all Baccharis species. This constituent in isolation, as well as the EOs of B. calvescens, B. mesoneura, and B. oblongifolia, caused mortality in over 80% of adults of D. suzukii at a discriminatory concentration of 80 mg L^-1 in bioassays of ingestion and topical application. These results are similar to the effect of spinosyn-based synthetic insecticides (spinetoram 75 mg L^-1) 120 h after exposure. Limonene and EOs from all species had the lowest LC₅₀ and LC₉₀ values relative to spinosyn and azadirachtin (12 g L^-1) in both bioassays. However, they showed the same time toxicity over time as spinetoram when applied to adults of D. suzukii (LT₅₀ ranging from 4.6 to 8.7 h) in a topical application bioassay. In olfactometry tests, 92% of D. suzukii females showed repellent behavior when exposed to the EOs and limonene. Likewise, the EOs of B. calvescens, B. mesoneura, and B. oblongifolia significantly reduced the number of eggs in artificial fruits (≅ 7.6 eggs fruit^-1), differing from the control treatment with water (17.2 eggs fruit^-1) and acetone (17.6 eggs fruit^-1). According to histological analyses, the L3 larvae of D. suzukii had morphological and physiological alterations and deformations after exposure to treatments containing EOs and limonene, which resulted in high larval, pupal, and adult mortality. In view of the results, Baccharis EOs and their isolated constituent, limonene, proved to be promising alternatives for developing bioinsecticides to manage of D. suzukii.