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Knowledge of the distribution and abundance of resident parasitoid species of Drosophila flies constitutes an important base for developing and implementing a biological control program for Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), an invasive pest that attacks ripening thin-skinned wild and cultivated berries and stone fruits. For this purpose, a field survey was conducted to identify the parasitoid community associated with D. suzukii infested sites in tart cherry orchards and woodlots in west, northwest, and central Michigan. Sentinel traps baited with D. suzukii larvae and pupae in banana slices were deployed in the center of tart cherry orchards, in woodlots adjacent to tart cherry orchards, and in woodlots isolated from any known commercial host of D. suzukii. Traps were placed from the beginning of July to the end of October 2021. Three parasitoid species that are known to use drosophilids as hosts were recovered from these traps. Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Leptopilina boulardi Barbotin, Carton & Keiner-Pillault (Hymenoptera: Figitidae) emerged from the infested bananas. Leptopilina heterotoma (Thomson) was collected as an adult in a sentinel trap. Among these wasps, only P. vindemiae successfully parasitized D. suzukii pupae in the laboratory. This pupal parasitoid was abundant and widely distributed in both cherry orchards and woodlots. The highest number of P. vindemiae was collected from orchards, followed by woodlots adjacent to orchards, with woodlots without nearby cultivated fruit having the lowest detections. These findings suggest that future release of augmentative or classical biological control agents for D. suzukii could be successful in orchards postharvest to control late-season populations of this pest. [ABSTRACT FROM AUTHOR]

Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae) is a vinegar fly native to East Asia that has rapidly expanded its range to become a pest of sweet cherry (Prunus avium, L. 1753 [Rosales: Rosaceae]) and tart cherry (P. cerasus, L. 1753) in North America and Europe. The goal of the research presented herein was to improve the decision-making process for managing D. suzukii in tart cherry. Knowing that D. suzukii females are attracted to ripening fruit, we measured fruit infestation by D. suzukii as it relates to an existing fruit development model that uses full bloom as a biofix, calculating accumulated growing degree days (GDD) with a lower threshold of 4°C. Increasing larval infestation was highly correlated with fruit development expressed as GDD post-bloom with very few larvae developing in fruit subjected to no-choice assays prior to 530 GDD (base 4°C) and no larvae detected in naturally infested fruit prior to 800 GDD. Our findings provide the first quantification of the relationship between fruit development and D. suzukii infestation that allows for pinpointing the timing of fruit susceptibility and that could be used as the basis for a more sustainable management program for this pest in tart cherry orchards. [ABSTRACT FROM AUTHOR]

Frugivorous birds impose significant costs on tree fruit growers through direct consumption of fruit and grower efforts to manage birds. We documented factors that influenced tree fruit bird damage from 2012 through 2014 with a coordinated field study in Michigan, New York, and Washington. For sweet cherries, percent bird damage was higher in 2012 compared to 2013 and 2014, in Michigan and New York compared to Washington, and in blocks with more edges adjacent to non-sweet cherry land-cover types. These patterns appeared to be associated with fruit abundance patterns; 2012 was a particularly low-yield year for tree fruits in Michigan and New York and percent bird damage was high. In addition, percent bird damage to sweet and tart cherries in Michigan was higher in landscapes with low to moderate forest cover compared to higher forest cover landscapes. 'Honeycrisp' apple blocks under utility wires were marginally more likely to have greater bird damage compared to blocks without wires. We recommend growers prepare bird management plans that consider the spatial distribution of fruit and non-fruit areas of the farm. Growers should generally expect to invest more in bird management in low-yield years, in blocks isolated from other blocks of the same crop, and in blocks where trees can provide entry to the crop for frugivorous birds. [ABSTRACT FROM AUTHOR]

Management of cherry leaf spot disease, caused by the fungus Blumeriella jaapii, with succinate dehydrogenase inhibitor (SDHI) fungicides has been ongoing in Michigan tart cherry orchards for the past 17 years. After boscalid-resistant B. jaapii were first isolated from commercial orchards in 2010, premixes of SDHI fungicides fluopyram or fluxapyroxad with a quinone outside inhibitor were registered in 2012. Here, we report widespread resistance to fluopyram (FluoR), fluxapyroxad (FluxR), and boscalid (BoscR) in commercial orchard populations of B. jaapii in Michigan from surveys conducted between 2016 and 2019. A total of 26% of 1610 isolates from the 2016–2017 surveys exhibited the fully-resistant BoscR FluoR FluxR phenotype and only 7% were sensitive to all three SDHIs. Practical resistance to fluopyram and fluxapyroxad was detected in 29 of 35 and 14 of 35 commercial tart cherry orchards, respectively, in surveys conducted in 2018 and 2019. Sequencing of the SdhB, SdhC, and SdhD target genes from 22 isolates with varying resistance phenotypes showed that BoscS FluoR FluxS isolates harbored either an I262V substitution in SdhB or an S84L substitution in SdhC. BoscR FluoR FluxR isolates harbored an N86S substitution in SdhC, or contained the N86S substitution with the additional I262V substitution in SdhB. One BoscR FluoR FluxR isolate contained both the I262V substitution in SdhB and the S84L substitution in SdhC. These mutational analyses suggest that BoscR FluoR FluxR isolates evolved from fully sensitive BoscS, FluoS, FluxS isolates in the population and not from boscalid-resistant isolates that were prevalent in the 2010–2012 time period. [ABSTRACT FROM AUTHOR]