Tritrophic interactions among onion plant-Thrips tabaci- predators considering intercropping onion and safflower at different patterns

Intercrops are a potential crop management practice for reducing pest populations and improving the biodiversity of arthropods. The impact of intercropping onion (Allium cepa L.) and safflower (Carthamus tinctorius L.) was investigated on tritrophic interactions of onion- Thrips tabaci Lind.—predators in 2022 and 2023 in Iran. The experiments were accomplished in a randomized complete block design with treatments of intercropping onion (O) and safflower (S) in three patterns of row alternation: 4O:2S, 4O:4S, and 4O:8S along with the sole cropping of onion and safflower. The three intercropping systems reduced the densities of larvae and adults of onion thrips compared with the onion sole cropping over the two growing seasons. Besides, the leaf damage index per plant decreased in the intercropping systems compared to the onion sole cropping, reaching the lowest value in 4O:4S and 4O:8S in two years. The total abundance of onion plant- or ground-dwelling predators was higher in intercrops than in the sole crop. Further, higher Shannon diversity indices for onion plant-dwelling predators (H′ ≥ 1.73) and ground-dwelling predators (H′ ≥ 1.30) were recorded in intercrops, especially 4O:4S and 4O:8S. The land equivalent ratio (LER) ranged from 1.26 for 4O:2S in 2023 to 1.32 for 4O:4S in 2022. Our conclusions showed that intercropping onion-safflower, especially in the patterns of 4O:4S and 4O:8S, promoted the biocontrol service of onion thrips and crop production compared with the sole crops. Therefore, 4O:4S and 4P:8S intercrops are effective practices for controlling onion thrips in fields.