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

Abstract

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is an invasive economic pest of soft-skinned and stone fruit across the globe. Our study establishes both a predictive generalized linear mixed model (GLMM), and a generalized additive mixed model (GAMM) of the dynamic seasonal phenology of D. suzukii based on four years of adult monitoring trap data in Wisconsin tart cherry orchards collected throughout the growing season. The models incorporate year, field site, relative humidity, and degree days (DD); and relate these factors to trap catch. The GLMM estimated a coefficient of 2.21 for DD/1000, meaning for every increment of 1000 DD, trap catch increases by roughly 9 flies. The GAMM generated a curve based on a cubic regression smoothing function of DD which approximates critical DD points of first adult D. suzukii detection at 1276 DD, above average field populations beginning at 2019 DD, and peak activity at 3180 DD. By incorporating four years of comprehensive seasonal phenology data from the same locations, we introduce robust models capable of using DD to forecast changing adult D. suzukii populations in the field leading to the application of more timely and effective management strategies.

Global analysis of the seasonal abundance of the invasive pest Drosophila suzukii reveal temperature extremes determine population activity potential

“…Rather than simply using a single thermal threshold limit, we employed the widespread concept of degree‐days, as it combines severity of thermal exposure with duration. This is a standard method in crop management, such as timing insecticide treatments to coincide with predictions of high pest pressure, 50 and recently, physiologically based predictive DD models have been employed to forecast local D. suzukii phenology with varying success 27,28,44,51 . These models typically ignore temperature accumulation outside extremes and, rather, focus on temperature accumulation within the range that permits development.…”

“…These models typically ignore temperature accumulation outside extremes and, rather, focus on temperature accumulation within the range that permits development. For example, Kamiyama et al ., 28 implemented temperature accumulation between a lower limit of 7.2 °C and an upper limit of 30 °C, because D. suzukii development ceases outside those temperatures 52 . This is akin to using optimum temperatures as described above.…”

“…Environmental covariates for each monitoring point were constructed from the climatic data, including the mean temperature across the preceding 30 days, as well as the accumulated degree‐days (DD) both below 5 °C and above 25 °C 27,28 . These temperature thresholds approximately represent the lower temperature bounds of development and the decreasing phase of population growth rate, respectively 9 .…”

Seasonal monitoring of Drosophila suzukii and its non‐crop hosts in Wuhu, Eastern China

“…This identification will allow practitioners the management of these non‐crop habitats to reduce D. suzukii populations in surrounding crops (Langille et al., 2016). Precise prediction of the population dynamics of D. suzukii is difficult; however, some researchers are using generalized linear mixed models and a generalized additive mixed model to forecast changes in D. suzukii populations, which could assist in producing timely and effective management strategies (Kamiyama et al., 2020).…”

“…however, some researchers are using generalized linear mixed models and a generalized additive mixed model to forecast changes in D. suzukii populations, which could assist in producing timely and effective management strategies (Kamiyama et al, 2020).…”