To Every Thing There Is a Season: Phenology and Photoperiodic Control of Seasonal Development in the Invasive Caucasian Population of the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae)

Simple Summary The brown marmorated stink bug originates in East Asia and recently invaded Europe and North America. It is considered a serious pest because it damages 300+ species of wild and cultivated crops. Studies on the seasonal development of local populations of invasive insects are important for monitoring damage and predicting their dispersion. We investigated the seasonal development of this pest in Sochi (Krasnodar Territory, Russia) from 2018 to 2021 by regular field sampling. The results suggest that the brown marmorated stink bug normally produces two generations per year in the studied region: the main period when overwintered females lay eggs occurs from June to July; the second period of egg-laying (by females of the new generation) occurs in August. Reproductively active adult bugs were recorded from the end of May to the beginning of September. Such seasonal activity correlates with day length: when days became shorter than the experimentally determined critical value (15.0-15.5 h), the proportion of females with fully developed reproductive organs sharply dropped to zero. The timing of the beginning of the winter dormancy observed under the natural conditions agrees with the predictions based on the results of the earlier conducted laboratory experiments. Studies on the phenology of local populations of invasive insects are necessary for monitoring and predicting their dispersion. We investigated the phenology of the brown marmorated stink bug, Halyomorpha halys, in the Sochi region (Krasnodar Territory, Russia) from 2018 to 2021 by regular field sampling and dissecting. The results of the sampling suggest that H. halys is at least partially bivoltine in the studied region: the main period of mass oviposition (by the overwintered females) occurs from June to July; the second, much shorter period of egg-laying (by females of the new, i.e., the first generation) occurs in August. Reproductively active individuals (i.e., females with developed ovaries and filled spermatheca and males with filled ectodermal sac) were recorded from the end of May to the beginning of September. Such a seasonal pattern correlated with day length: when the natural photoperiod decreased below the experimentally determined critical day length (15.0-15.5 h), the proportions of females with fully developed ovaries sharply dropped to zero. Both the rate of H. halys pre-adult development and the timing of the induction of winter adult diapause observed under natural conditions fully agreed with the earlier predictions that had been based on the results of laboratory experiments.