INFLUENCE OF IRRIGATION ON APHID INFESTATION IN MAIZE

Abstract

Maize (Zea mays L.) is a crucial crop for both Ukraine and the global agricultural sector, serving as a key staple and export commodity. Ukraine ranks among the top ten maize producers worldwide, with annual production reaching 27-35 million tons and exports of 20-25 million tons. Irrigation significantly enhances maize yield, potentially increasing productivity from 6,8-7,0 tons per hectare to 12-15 tons per hectare. Given the importance of maize for food security, economic stability, and international trade, understanding factors that influence its productivity is essential. One of the major challenges in the Steppe, Forest-Steppe, and Polissia regions of Ukraine is the irregular water regime, which limits the full utilization of soil potential. Effective irrigation management not only improves water use efficiency and soil health but also promotes the proliferation of beneficial organisms, contributing to increased crop resilience. This study, conducted from 2020 to 2023 in the Kyiv region, investigated the development and population dynamics of aphids (Aphididae spp.) on irrigated and non-irrigated maize, alongside the role of natural predators in regulating aphid abundance. Experimental plots of 50 m² were established using a randomized design with four replications. The maize hybrid P9074 (FAO 330) was grown under controlled irrigation with water-jet sprinklers, while control plots relied on natural precipitation. Meteorological data, including air temperature, precipitation, and the Selyaninov hydrothermal coefficient (SHC), were recorded to assess their impact on aphid population density. Results indicated that aphid infestation was higher on irrigated plots, particularly during the tassel emergence and flowering stages. Average infestation in irrigated areas reached 47,8 % during maize ripening, compared to 42,8 % in non-irrigated fields. A moderate negative correlation was found between precipitation and aphid infestation (r = -0,34), while a weak positive correlation existed with air temperature (r = 0,19). Irrigation was found to modify the microclimate significantly, reducing air temperature by 2,4-6,1 °C and increasing humidity to 78-100 %, depending on timing and water volume, with nocturnal irrigation producing the most gradual changes. In addition, irrigation enhanced the abundance of natural aphid predators. Populations of Coccinellidae and Chrysopidae were 2,2 and 1,7 times higher, respectively, in irrigated fields compared to non-irrigated plots. Key predator species, including Chrysopa carnea Steph., played a critical role in controlling aphid populations, demonstrating that irrigation can indirectly support biocontrol mechanisms. Overall, the study highlights that irrigation not only increases maize productivity but also influences aphid population dynamics and predator activity. These findings emphasise the importance of integrated water and pest management strategies to optimise crop yields and strengthen the ecological resilience of maize agroecosystems in Ukraine.