Varietal and Developmental Susceptibility of Tart Cherry (Rosales: Rosaceae) to Drosophila suzukii (Diptera: Drosophilidae)

Abstract

Drosophila suzukii (Matsumura) is an invasive species of vinegar fly that infests soft-skinned and stone fruits. Since its first detection in the United States, D. suzukii has become a prominent economic threat in fruit crop industries, particularly affecting caneberry and sweet cherry growers. This study examined the susceptibility of tart cherries (Prunus cerasus) to D. suzukii and sampled for larvae and adult D. suzukii during the tart cherry growing season. Four tart cherry cultivars (Montmorency, Balaton, Carmine Jewel, and Kántorjánosi) were tested at three different ripeness stages (unripe, ripening, and ripe), in no-choice laboratory bio-assays. Field monitoring and sampling revealed that first adult D. suzukii detection occurred on 16 June, and first field larval D. suzukii detection occurred on 28 July. Adult D. suzukii populations increased through late August, and high numbers of adults overlapped with the tart cherry harvest. Lab assays indicated that tart cherry cultivars generally became more susceptible to D. suzukii as they ripened. As the fruit developed, °Brix (sugar content) increased and firmness generally decreased. Tart cherry °Brix and firmness were not correlated with the number of D. suzukii eggs per gram of fruit, but showed a significant interaction effect with the number of larvae and adults per gram of fruit. This study shows that tart cherries are largely not susceptible to D. suzukii when unripe and become susceptible as soon as the fruits change color, suggesting that fruits should be protected as soon as they begin to ripen and D. suzukii populations begin to rise.

Degree day models to forecast the seasonal phenology of Drosophila suzukii in tart cherry orchards in the Midwest U.S.

“…The GAMM model generated a smoothed curve plot representing D. suzukii population tendencies throughout the growing season, which is valuable in determining periods of high or low risk for elevated D. suzukii numbers and phases of rapid population increase or decrease. The field population trends described from this work are characteristic of D. suzukii phenology in the Midwest, as studies in Wisconsin and Michigan fruit crops report first adult detection in the early summer, peak activity in the late summer, and decreasing populations in the early fall [13,23,26,31]. It is worth noting that in our study monitoring typically ceased a few weeks after tart cherry harvest, limiting our ability to extrapolate on the population trends beyond early fall and into winter.…”

“…The orchard which grew 'Balaton' was retained in the model because the 'Balaton' site had an average weekly trap catch throughout the four years (29.95 flies) that fell within the 95% confidence interval of the average weekly D. suzukii trap catch for all the sites throughout the four years (22.26-30.04 flies). Also, both 'Balaton' and 'Montmorency' cultivars had similar D. suzukii egg and larval infestation levels in lab assays from a previous study [26]. All orchards were conventionally managed for D. suzukii by rotating pyrethroid and organophosphate insecticides, averaging four to five applications throughout the growing season.…”

“…Insecticide applications are typically initiated with first D. suzukii detection in the early summer when fruit is beginning to ripen, and continue until the completion of harvest [10]. Our study, along with previous work done on D. suzukii phenology in the Midwest [13,23,26,31], acknowledge, but did not incorporate pesticide use as an effect when analyzing D. suzukii population dynamics, meaning the influence insecticide application has on trap catch in this region is largely unknown. Future models directed towards approximating the seasonal phenology of D. suzukii should consider all significant biotic and abiotic effects, including factors that remain unresolved such as D. suzukii overwintering habits, impact of native biological control, and host crop characteristics.…”

“…According to the GAMM, the first detection of D. suzukii is estimated to occur at 1262 DD, meaning control measures should be initiated when that DD accumulation is reached and fruit has reached a susceptible stage in a given year [26]. For reference, 1276 DD fell most closely on June 26 th , 24 th , 23 rd , and 22 nd in 2015, 2016, 2017, and 2018 respectively.…”

Morphometric criteria to differentiate Drosophila suzukii (Diptera: Drosophilidae) seasonal morphs

“…Native to east and southeast Asia, D. suzukii is an important economic pest of soft-skinned fruits (e.g., strawberries, raspberries, blueberries) and stone fruits (e.g. cherries, peach) [2][3][4][5][6]. Drosophila suzukii invaded the continental United States in 2008 and rapidly spread throughout the country [7], and has quickly become a global pest [2,8].…”