Effect of biopesticides on the spotted alfalfa aphid, Therioaphis trifolii Monell, and its predator, Coccinella septempunctata L.

Abstract

The spotted alfalfa aphid Therioaphis trifolii Monell (Hemiptera: Aphididae) is one of the most commonly found insect pests, affecting alfalfa crops and causing severe damage in Bulgaria. Natural products, such as botanical insecticides, serve as an excellent alternative to synthetic counterparts for pest management. The combined application of the biological insecticide pyrethrins (40 g L−1) and organic fertilizer phosphorus pentoxide + potassium oxide (30 and 20%, cumulative insect days of T. trifolii and an overall efficacy of 68.3%. The toxic effect was close to that of the synthetic insecticide thiacloprid (240 g L−1), although there was a significant difference. Plants treated with pyrethrins and organic fertilizer, followed by biofertilizer alone, exhibited the best physiological condition and a high content of plastid pigments, as the interaction between these two products was additive. The use of botanical products had a positive impact on the plant’s vegetative development. Among the bioproducts, the combined application of organic fertilizer and pyrethrins resulted in the highest productivity, with a 22.6% increase. Botanical products were harmless by toxicity not exceeding 25% against Coccinella septempunctata larvae. Their essential role is highlighted due to the numerous benefits. The combined use of pyrethrins and organic fertilizer is an approach to organic farming crucial for sustainable and environmentally friendly agricultural development. Botanical products are considered safe, eco-friendly alternatives that contribute to insect pest control and promote increased agricultural production.