The results of the potato cultivars study for resistance to the Colorado potato beetle using two field methods

The comparative resistance of 23 potato cultivars to the Colorado potato beetle Leptinotarsa decemlineata Say (Coleoptera, Chrysomelidae) was studied in 2019–2024 in the agro-climatic conditions of the centre of Leningrad Region, where this pest has been steadily found since 1998. The research was carried out in field experiments by two methods: 1) using the artificial colonization of the studied potato samples by larvae in the I age; 2) on the natural background of pest colonization of the experimental site. In the first case, the longevity of larval development and the whole preimaginal development of individuals and also the percentage of survived larvae in the IV age and the percentage of winged imagoes in relation to the number of colonized larvae in I age were determined. In the second case, the pest-resistant potato cultivars were screened by criterions of the level of pest abundance in all phases and the degree (point) of damage to the tops. According to the data of 2019–2024, the most pest-resistant potato cultivars were ‘Nayada’, ‘Sirenevy Tuman’ (Russia), ‘Red Fantasy’, ‘Fidelia’ (Germany). In experiments with artificial colonization of plants, the larval survival on these cultivars was usually observed at the level of 39–55 %, and the winged imagoes– at the level of 5–38 %. The same results were received on the cultivars ‘Gulliver’, ‘Pioner’, ‘Konkurent’ (Russia), ‘Grenader’ (Germany) and ‘Berkut’ (Kazakhstan), which were studied in 2024 for the first time. During the development, 19–54 % of larvae survived and 1.3–15.1 % of imagoes were winged, while 65–96 % of larvae and 34–69 % of imagoes survived on the non-resistant (most favorable for the pests) cultivars ‘Nevsky’, ‘Forward’, ‘Sarma’, ‘Alfa’, ‘Sadon’ and ‘Ariel’ (Russia). In 2024 against the natural background of insect colonization of plants on resistant cultivars 10–30 overwintered beetles and 250–440 larvae were found per 100 bushes, while on non-resistant cultivars, 35–87 beetles and 500–1600 larvae were found. These differences between resistant and non-resistant cultivars are significant at p<0.01. The identified resistant cultivars may be used as the basis of integrated potato protection systems that meet environmental safety requirements. The use of two field methods allows for a more objective screening of samples resistant to the Colorado potato beetle and for the characterization of the various effects of the fodder plant on the phytophage.