Infl uence of ecological factors on the start date of the colorado potato beetle lLeptinotarsa decemlineata (Say) (Coleoptera, Chrysomelidae) emergence from overwintering sites in the Central forest-steppe priobskii agro-landscape region

Abstract

As a result of long-term studies, the complex e ect of the depth of soil freezing, depth of snow cover, the amount of precipitation, the temperature of air and of soil at a depth of 0-20 and 20-40 cm, the sum of e ective temperatures on the start date of the adult Leptinotarsa decemlineata (Say) emergence from the soil in potato plantings was established in the Central Forest-Steppe Priobskii Agro-Landscape Region. The average values of these environmental factors for the period from September of the previous year to June of the current year by 27.2% determined the emergence date of the overwintered imago. The share of the conditions of the previous year in uence was 50.5, and the conditions of the current year, 31.1%. The appearance of the overwintered adults was delayed when they had gone for overwintering in moist and cool soil. In November, the emergence date begins to be a ected by the depth of snow cover and the depth of soil freezing (the in uence shares 86.8 and 79.5%, respectively), and their e ect together with the factors listed accounted for 35.3%. In December, the same trend was observed, but the air temperature was not considered. In January, the importance of the parameter of the soil temperature increased to 84.3%, and that of the complex of factors in 26.7% of cases. In February, the same trend was observed, and the share of the in uence all previously listed factors increased to 43.0%. From March, the impact of the depth of soil freezing and the depth of snow has decreased to 42.3%, and from April, the sum of rain precipitation and air temperature began to in uence in 81.8 and 65.8% of cases, respectively. In May, the start date of the pest appearance is a ected only by the soil temperature at a depth of 0-20 and 20-40 cm - 80.7 and 94.0%, respectively, and by photoperiod - 91.1%. In June, the main factors were the amount of rain precipitation and the soil temperature - 100%, while the impact of accumulated SET was 50.0%. Thus, in this region, on average, the beginning of the adults’ Exit from the soil starts on June 17 ± 12 days, when the average daily air temperature reaches +19.1 ± 5.8 °C, the sum of rain precipitation (at air temperature > 10 °C) - 70.7 ± 39.1 mm, and the soil at a depth of 0-20 and 20-40 cm warms up to +17.6 ± 3.8 °C and +14.8 ± 2.5 °C, respectively. The SET in this period is 149.0 ± 64.1 degree days.