Effect of Insecticides on Phytophagous Insects, Predatory Coccinellids and Field Yield of Corn (Zea mays)

Abstract

Corn (Zea mays Linnaeus) is a relevant cereal in the human diet. Because insect pests justify the frequent use of synthetic insecticides, it is necessary to evaluate more sustainable alternatives. Therefore, this study aimed to estimate the effect of various insecticides on pest control, predatory coccinellids, and crop yield. From November 2021 to September 2022, two 1,000 m² plots were planted (rainy and dry seasons) and the following treatments were evaluated: 1. Acephate alternated with chlorpyrifos (AC); 2. Azadirachtin; 3. Bacillus subtilis + Bacillus pumilus; and 4. Untreated control. Individuals of Rhopalosiphum maidis, Frankliniella occidentalis, and predatory coccinellids were counted. In addition, damage to plants and cobs caused by Spodoptera frugiperda and Helicoverpa zea, respectively, was evaluated. Rhopalosiphum maidis populations were lower in the AC and azadirachtin treatments. Frankliniella occidentalis populations did not differ between treatments. Plant damage was lower with all insecticides evaluated, while AC and azadirachtin controlled cobs damage. Yields were higher with AC and azadirachtin. The diversity and abundance of predatory coccinellids were drastically affected by synthetic insecticides, necessitating a thorough economic, environmental, and social analysis to address pest management challenges within a sustainable framework. Environmental conditions must also be considered, given that the pest that most limited maize yield (Helicoverpa zea) was more prevalent during the rainy season.