The Protein Paradox: Elucidating the Complex Nutritional Ecology of the Invasive Berry Pest, Spotted-Wing Drosophila (Diptera: Drosophila suzukii)

Spotted-wing drosophila (SWD), Drosophila suzukii, has become one of the most widely studied insect species over the last decade, largely due to its recent invasion and rapid expansion across the Americas and Europe. Unlike other drosophilid species, which colonize rotting fruit, SWD females possess a serrated ovipositor that allows them to lay eggs in intact ripening fruit, causing significant economic problems for fruit/berry producers worldwide. Though an impressive amount of research has been conducted on SWD's ecology and physiology, aspects of their nutritional ecology remain ambiguous. This review synthesizes the research to date to provide a more comprehensive view of SWD's nutritional relationship with its fruit hosts and associated microbes. Overall, data suggest that SWD's ability to utilize novel resources is likely due to changes in their ecological, rather than physiological, niche that are largely mediated by microbial associations. Studies show that SWD's nutrient intake is comparable to other drosophilid species, indicating limited adaptation to feeding on lower-protein resources. Instead, data show that fruit protein content is a reliable predictor of host suitability and that fruit-microbe dynamics have a strong impact on protein availability. In particularly, fruit protein increases after infestation with SWD-associated microbes, suggesting that initially-suboptimal intact fruits can become protein-rich on a timeframe that is relevant for larval nutrition. This body of work suggests that microbial associations between flies and their fruit hosts can compensate for the nutritional differences between intact and rotting fruit, and that these relationships are likely responsible for SWD's expanded nutritional niche.

POPULATION DYNAMICS OF DROSOPHYLA SUZUKII (MATSAMURA) IN SWEET AND SOUR CHERRY ORCHARDS IN THE CENTRAL BALKANS MOUNTAIN

The spotted wing drosophila (SWD) Drosophila suzukii, Matsumura is a polyphagous for many stone and soft fruits species. The pest was recorded in 2014 at sweet cherry orchards in our country and has become a real pest, because SWD attack the fruit when they start to ripe. During 2017-2019 the study was carried out in the Institute of Mountain Stockbreeding and Agriculture in Troyan – Central part of the Balkans Mountain. For monitoring were used traps with red wine and apple vinegar. The first flies at the sweet cherry were found during the second decade of May and in the sour cherry - a little later, at the beginning of June, when the fruit start to ripe. The peak of the population dynamics was established in the second half of June, after which the density began to decreasing. It was found that D. suzukii was preferred more the sweet cherry fruits than sour cherry fruits.

Adventive larval parasitoids reconstruct their close association with spotted-wing drosophila in the invaded North American range

Two species of larval parasitoids of the globally invasive fruit pest, Drosophila suzukii (Diptera: Drosophilidae), Leptopilina japonica and Ganaspis brasiliensis (both Hymenoptera: Figitidae), were detected in British Columbia, Canada in 2019. Both are presumed to have been unintentionally introduced from Asia, however; the extent of their establishment across different habitats with diverse host plants used by D. suzukii was unclear. In addition, there was no knowledge of the temporal dynamics of parasitism of D. suzukii by these two parasitoids. We repeatedly sampled the fruits of known host plants of D. suzukii over the entire 2020 growing season in British Columbia. We documented the presence of L. japonica and G. brasiliensis and estimated the apparent percentage of D. suzukii parasitized. Across a large region of southwestern British Columbia, both L. japonica and G. brasiliensis were found to be very common across a variety of mostly unmanaged habitats over the entire course of the season (May-October) in the fruits of most host plants known to host D. suzukii larvae. The two parasitoids were responsible for more than 98% of D. suzukii larval parasitism and usually co-existed even within a host species. Parasitism of D. suzukii was variable among hosts plants and sites (0-66% percent parasitism) and appeared to be time-structured. Our study demonstrates that the close association between the two larval parasitoids and D. suzukii that exists in Asia has evidently been reconstructed in North America, resulting in the highest parasitism levels of D. suzukii yet recorded outside of its area of origin.

Acttra SWD Bait Formulation Against Drosophila Suzukii and its Compatibility with Berry Pollination by the Honey Bee, Apis Mellifera

Crop protection substances are continuously developed to prevent the decimation of non-target insect populations through insecticide use. The bait formulation Acttra SWD was created to attract the adult spotted-wing drosophila, a generalist pest of berries, and when mixed with insecticide would cause a reduction in the volume of insecticide applied, thus avoiding a complete coverage of crops and resulting in economic and ecological benefits to society. However, Acttra SWD has some compounds, including sugars and fruit odors, that might attract non-target fauna, especially insect pollinators. Therefore this study aimed (1) to investigate if Acttra SWD mixed with the recommended pesticide, i.e. spinosad (Entrust), is attractive to the honey bee, which is extensively used for berry pollination and (2) to evaluate the insecticidal activity of Acttra/Entrust in oral and contact tests on the same species. In all replicates, most foragers rejected feeders that offered Acttra/Entrust, and some switched to Acttra/Entrust-free feeders. Accordingly, mortality caused by this mixture in oral tests was low and did not differ from control, since the majority of bees did not consume the Acttra/Entrust treatment. However, mortality caused by this mixture was higher than in control groups in topical tests. Our results indicate that honey bees will not be attracted to and poisoned by crops sprayed with Acttra/Entrust, but contact with the bait would result in lethal or sub-lethal effects.

EFFICIENCY OF ATTRACTORS AND TRAPS FOR CAPTURE OF SPOTTED-WING DROSOPHILA IN VINEYARDS1

ABSTRACT Pest monitoring is a practice that enables the estimation of populational density of insect-pests in crops. However, it requires the use of attractors and traps that present high efficiency. The objective of this work was to evaluate the efficiency of food attractors using different trap models for the capture of spotted-wing drosophila (Drosophila suzukii) insects, and the capture selectivity of these models in vineyards of Cabernet Sauvignon. The experiment was conducted in the 2018-2019 crop season, in São Joaquim, SC, Brazil. A randomized block design was used, in a 2 × 4 factorial arrangement consisted of two types of traps (PET bottle and plastic container), three attractors (SuzukiTrap®, Droskidrink, and Yeast), and distilled water as a control. The traps were distributed in a minimum distance of 15 m and fixed in the middle third of the plants. The collections and replacing of attractors were done with 21-day intervals. The data were analyzed through generalized linear models, using the Poisson distribution or Poisson with a dispersion parameter. All attractors tested captured adult D. suzukii insects. No significant differences were found between the trap types used. The findings of the present work showed that the trap plastic container with the Droskidrink attractor is the most suitable capture method to be used in monitoring programs for D. suzukii insects in commercial vineyards.

Efficacy and Phytotoxicity Assessment of Successive Application of Methyl Bromide and Cold Treatment on Export Strawberry Fruits

Recently, spotted wing Drosophila, Drosophila suzukii, is globally prevalent and causes agricultural losses to many fruits. To export Korean strawberry, methyl bromide fumigation is required to remove D. suzukii infestations, but Korean strawberry farmers are worried about fruit damage because methyl bromide can cause phytotoxicity on fresh commodities. In this report, we assessed the efficacy and phytotoxicity of single and successive application of methyl bromide and cold treatment on an export variety of strawberry to reduce fruit damage. The currently recommended dosage of methyl bromide, 40 g/m3 for 3 h at 18 °C, was enough to control all stages of D. suzukii without phytotoxicity. A dosage of 20 g/m3 of methyl bromide treatment for 3 h, followed by 1 d of cold (0 °C) treatment, showed 100% mortality in all growth stages of D. suzukii without fruit damage. Successive application of methyl bromide and cold treatment shows potential as a method of decreasing phytotoxicity and reducing the use of methyl bromide for environmental considerations.

First record of Spotted-wing drosophila Drosophila suzukii (Diptera: Drosophilidae) in Martín García Island wildlife refuge, Argentina

Here we report on the first peculiar detection of the spotted-winged drosophila, Drosophila suzukii (Matsumura) on Martín García Island, a wildlife refuge located in the Río de la Plata estuary, Argentina. Flies were collected using banana baited traps fermented with live yeast, in sandy areas with abundant presence of cactus in the interior of the island. The absence of cultivated host plants, e.g., fruit crops, and the small population of humans inhabiting the island make the presence of D. suzukii in this wildlife refuge unexpected. Previous detection of this fly in South America happened mostly within commercial fruit orchards and/or neighboring fields.