Grapholitha molesta is an important fruit pest in apple orchards in southern Xinjiang, which seriously affects the yield and quality of apple. The influence of agricultural landscape configuration and composition on the population number of G. molesta in apple orchards was clarified to provide a theoretical basis for the rational design of agricultural landscape that reduces the harm of G. molesta under the adjustment of cropping structure in southern Xinjiang.

A total of 50 apple orchards were selected as experimental sites in Aksu area from 2017 to 2020. The landscape composition within a radius of 2.0 km of each site was investigated. The insect sex pheromone traps were used to investigate the population dynamics of G. molesta adult. Regression models of Shannon diversity index (SHDI), perimeter area ratio (PARA), edge density (ED), and the area proportion of non-crop habitats, host crops and other (non-host) crops in landscapes at four scales (0.5, 1.0, 1.5 and 2.0 km) were fitted with the number of adults of the first, second and third generations in apple orchards.

In the study area, the proportion of host crops was highest (45.7%-55.0%), followed by other crops (18.2%-21.0%) and non-crop habitats (13.5%-19.7%). There was a negative correlation between the abundance of the first generation adult and the proportion of other crops at 2.0 km scale (P=0.062). The abundance of the second generation was negatively correlated with other crops at four scales (0.5 km, P<0.001; 1.0 km, P<0.001; 1.5 km, P=0.028; 2.0 km, P=0.043), negatively correlated with the proportion of host crops at 1.0 and 1.5 km scales (1.0 km, P=0.026; 1.5 km, P=0.048), negatively correlated with the proportion of non-crop habitats at 0.5 and 1.0 km scales (0.5 km, P=0.023; 1.0 km, P=0.019), but positively correlated with Shannon diversity index (SHDI) (0.5 km, P<0.001; 1.0 km, P=0.005). The abundance of the third generation was negatively correlated with the proportion of non-crop habitats at 0.5 km scale (P<0.001).

Increasing the proportion of host crops, other crops, and non-crop habitats within agricultural landscape decreased the occurrence of G. molesta in apple orchards. However, landscape diversity (Shannon diversity index) promoted the population number of G. molesta. Therefore, increasing the area of the other crops and non-crop habitats coupled with no mixed planting of host crops in landscapes could be beneficial to the management of G. molesta.

Thrips is a major pest in cotton fields in Xinjiang. The objective of this study is to select their dominated predatory natural enemies and assess the predation efficiency on thrips, and to provide scientific insights for the development of biocontrol on thrips in cotton fields.

The population dynamics of thrips and their predators in Korla cotton field in southern Xinjiang were systematically investigated by visual inspection within five-point sampling in different blocks from 2021 to 2022. Predators’ samples were collected at different growth stages of cotton fields and detected by molecular detection, DNA of the whole natural enemy was extracted first, and PCR amplification was performed using the specific primers of Thrips tabaci and Frankliniella intonsa to obtain the species information of thrips in various natural enemies, then the quantitative food web of predator-thrips was constructed, and the differences of related food web structure at different growth stages of cotton were compared. In addition, basing on the predator-prey functional response model, the predation function of different predators (including adults and juveniles) on thrips was evaluated in laboratory by setting the prey density of 50, 100, 200, 300 and 400 individuals per Petri dish.

The population density of thrips was low at the seedling and budding stages but was high at the flowering-bolling stage. Annual population peaks occurred from late-July to early-August. Basing on the population dynamic, Hippodamia variegata is the dominated predator for thrips that occurred across the seeding, budding, flowering and bolling stages, while Campylomma diversicornis is the dominated predator in the late of flowering-bolling stage. The results of molecular detection showed the detection rate of thrips was high in the gut of H. variegata in the whole growth period of cotton, the detection rate of thrips in the gut of Coccinella undecimpunctata at seeding-budding stage was high, and the detection rate in the gut of C. diversicornis was also high at flowering-bolling stage. The predatory function response in laboratory indicated the predation ability of different predators on F. intonsa increased with the increase of prey density, the predation function of the larvae of H. variegata, the nymph of C. diversicornis and the larvae of Chrysoperla carnea was consisted with the Holling-Ⅱ model, whereas the predation function of the adult, such as H. variegata and C. diversicornis was suited with the Holling-Ⅲ model; when high prey density of 400 individuals thrips per Petri dish was provided, the consumed number of thrips for the adult of H. variegata was significantly higher than the larvae, the adult and nymph of C. diversicornis and the larvae of C. carnea.

H. variegata is the dominant predator for thrips across the whole cotton growth period, and C. diversicornis is the dominant predator in the late of flowering-bolling stage. This study provides a scientific insight for the utilization of predators to suppress thrips in cotton fields in Xinjiang.