The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar’s Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion.

Synergy between the entomopathogenic fungus Metarhizium robertsii J.F. Bisch., S.A. Rehner et Humber and a complex of natural avermectins was observed after combined treatment of the Leptinotarsa decemlineata (Say) larvae. This effect was also recorded at the larval stage most resistant to fungi (5 days after molting to the IV instar). Intoxication with avermectins led to a 2.7-fold decrease in food consumption and arrest of larval development. Synergy between the fungus and avermectins was revealed in field experiments conducted in the steppe zone of Western Siberia under strong fluctuations of temperature and humidity. In particular, the median lethal time (LT₅₀) decreased 2.8-fold after combined treatment as compared to treatment with M. robertsii alone. The mechanisms of synergy and the prospects of using the combined treatment for Colorado potato beetle control are discussed.

Baculoviruses can persist in insect host organisms after infection and may be vertically transmitted to the next generation, in which they may be reactivated. The goal of the present study was to compare the efficiency of the vertical transmission of high- and low-virulence strains and the subsequent reactivation of Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) in the offspring of Lymantria dispar L. adults who survived after viral infection. As a result of parental infection, the fecundity of survived females, pupae weight, and fertility were significantly different compared to the untreated insects. However, differences in these parameters between high- and low-virulence strains were not observed. The prevalence of virus strains in the offspring measured by quantitative polymerase chain reaction also did not differ. When the larvae reached the fourth instar, they were starved to activate the vertically transmitted virus. The frequency of virus activation in the experiment was not dependent on the virulence of the virus strains. These results are helpful for understanding the strategy of virus survival in nature and for the selection of the most effective strains with transgenerational effects in the years following pest treatment.

The goal of this study is to detect indicators of damage to birch stands in western Siberia by spongy moth (Lymantria dispar L.) using remote sensing methods. The need for such indicators is due to the fact that the size of the study area is about 1 million square kilometers, and ground methods are too laborintensive. It is crucial for these indicators to differentiate the effects of insects from other destructive factors like fires and droughts. During the 2021–2022 fieldwork, we identified 18 areas for trial (intensive damage due to caterpillars) and control. For each area, we obtained seasonal time-series data of vegetation index NDVI mean values within its boundaries. We acquired the data from a Sentinel-2 satellite with a spatial resolution of 10 m. Relative reduction indices of NDVI during the season were introduced for pairs of damaged–control plots. We also considered the effect of foliage regeneration on damaged trees. The obtained indicators demonstrate increased analytical significance in identifying areas affected by pests compared to the simple reduction in vegetative indices.