FEATURES OF THE DEVELOPMENT OF THE COTTON BOLLWORM HELICOVERPA ARMIGERA HB. (LEPIDOPTERA: NOCTUIDAE) ON SUNFLOWER IN THE FOREST-STEPPE OF UKRAINE

Abstract

The purpose of the article is to clarify the development features of the cotton bollworm (Helicoverpa armigera Hb.) on sunflower crops in the conditions of the Forest-Steppe of Ukraine. It will allow to plan and apply protective measures against this pest more effectively, that is relevant. Methods. Field research was conducted according to generally accepted methods during 2021–2024 in the conditions of Boryspil district Kyiv region on sunflower crops. During the growing season, phenological observations and scores of pest damage to crop plants were collected. Constant monitoring of the flight of cotton bollworm adults was provided using pheromone traps and troughs with noisy molasses. Measurements of entomological material to determine the instar of larvae were carried out. The results. Analyzing the weather conditions of 2021–2024, a significant increase in the average air temperature in 2024 compared to the long-term norm should be noted. The accumulation of the sum of effective temperatures (SET) more than 12 °C reached 1160 °C already at the end of August 2024. It was almost one month earlier compared to the previous year. SET>12 °C reached 1157 °C at the end of September 2023, exceeding the corresponding indicator of 2021 (1078.6 °C) and 2022 (974.4 °C). Peculiarities of cotton bollworm development on sunflower crops under the conditions of the Forest Steppe of Ukraine were studied. The flight beginning of the first-generation imago and the start of egg laying occurred in the third decade of May. Development of caterpillars took place from the end of May to the third decade of June – the first decade of July. Their pupation occurred at the end of June – the first decade of July, before the beginning or coinciding with the beginning of sunflower flowering. An appearance of the second-generation imago from pupae took place in the third decade of July. The mass laying of eggs and flight of more than 50 % of the butterfly population occurred in the middle of July – the beginning of August, which coincided with the flowering – ripening phase of the sunflower. The terms of the second-generation larvae development occurred in the end of July – the 1st–3rd decades of August. Caterpillars of older and younger instars were found at the same time at observations and scores. Their pupation took place in the 2nd decade of August – the 1st decade of September, coinciding with the seed ripening phase – the full ripening of the sunflower. Due to the hot conditions of 2024, there was a shift in the terms of the appearance of pest development stages to earlier ones. Clarification of the sum of effective temperatures required for different stages of the pest development will allow to predict and plan protective measures against this pest in field conditions. Conclusions. In 2021–2023, the appearance of the first-generation imago Helicoverpa armigera Hb. from overwintered pupae took place in the third decade of May (SET>12 °C=83.5-88.1 °C). Mass laying of eggs and flight of more than 50 % of the butterfly population occurred in the 1st–2nd decades of June (SET>12 °C=174.3-178.7 °C), which coincided with the phase of 6–8 pairs leaves of sunflower. The flight of the first adults of the second generation took place in the third decade of July 2021-2023 (SET>12 °C=587.3-617.8 °C). The mass flight of imago and laying of eggs occurred at the beginning of August (SET>12 °C=680.3–703.6 °C), which coincided with the sunflower ripening phase. Due to the hot conditions of 2024, there was a shift in the terms of phytophagous development stages to earlier ones. This difference in terms ranged from 6 days to 2 weeks compared to 2021–2023. An accumulation of SET>12 °C (1120–1160 °C) in 2023–2024 was sufficient for the appearance of third-generation imago from pupae and their flight.