Planting functional plants in cotton fields enhances natural enemy populations, improving biocontrol of cotton pests and increasing cotton yield

Intensive agriculture has reduced farmland biodiversity and impaired sustainable pest control. Although planting functional plants is a key strategy for restoring farmland ecosystem balance, its specific ecological effects have yet to be clarified. From 2024–2025, monoculture and mixed plantings of Cnidium monnieri , Lobularia maritima , and Ammi visnaga were established at cotton fields to determine their regulatory effects on major pests, natural enemies, and yield of cotton. All three-species plants and their combination supported seven common predatory natural enemies. At distances of 0.5–22.5 m from functional plant strips, Aphis gossypii and Frankliniella intonsa populations were significantly lower than those in the control plot located 50 m away from the sampling area, while Hippodamia variegata populations were significantly higher. DNA detection showed that the detection rates of A . gossypii and F . intonsa predated by H. variegata were significantly lower in plots planted with three functional plants and their combination than in control plots in July. In contrast, no significant differences were observed in the detection rates for H . variegata and Orius sauteri across all treatments in June and August. Compared with the control, C. monnieri , A. visnaga and the combination increased cotton bolls per plant and seed cotton yield, with 11% higher number of bolls in A . visnaga and 7% higher seed cotton yield in combination plots. This study confirmed that planting functional plants achieves conservation biological control and increases cotton yield, providing a scientific basis for sustainable cotton production.