Kurdyukova E.A., Kurdyukov A.B
Amurian zoological journal 2021; 13(4): 438-459
The settling of 28-spotted Potato Ladybird (28SPL) Henosepilachna vigintioctomaculata in the North, with the transition to nutrition on potato crops, is limited by the complex impact of climatic factors. To identify the correlation between the weather conditions of the Primorsky Territory and the biological and phenological parameters in the development of 28SPL, we conducted the analysis of data collected over a twenty-year span (from 1999 to 2018) in various parts of the region. We carried out the calculation of 136 pairwise correlations, 22 of which turned out to be statistically significant. The analysis showed that the average air temperatures of 28SPL entering overwintering and on dormancy release were found to be 2-4°C lower than those stated in the literature: +11.2°C and +10.7°C, respectively. In the years with cool and rainy autumns, 28SPL enter overwintering later. We found the correlation between the weight of beetles entering overwintering, the index of winter severity and the beetle death during winter. The overwintering survival rate in different years ranged from 55-79 to 82-93%. The dormancy release takes place when the average daily temperatures pass the threshold value. However, it does not correlate with the average monthly temperature background. The mass egg-laying of 28PL accelerates if the beetles reach potato crops later than usual. The development of the new 28SPL generation takes from 39 to 60 days. This period may last shorter at the stage of egg development. Thus, the possibility of producing the second generation per season in the Primorsky Territory is limited. The observed indices of the 28SPL abundance were minimal at the beginning of the growing season; they gradually increased by the end of June due to the concentration from the surrounding biotopes; a sharp increase in the abundance of adults in early July is associated with the emergence of a new generation of beetles. The abundance of 28SPL reaches its maximum by September. The study identified a positive correlation between the number of adult 28SPL and an increase in heat supply in June; on the contrary, heavy rainfall has a pronounced negative effect on the beetle population numbers.
