The cotton aphid, Aphis gossypii, is an important insect pest of many crops around the world, and it has developed resistance to a large number of frequently used insecticides. The sublethal effects of insecticides not only have an environmental risk to arthropods but also have the potential to promote resistance evolution. The sublethal effects (inhibitory or stimulatory) are influenced by many factors, such as the type of insecticide, sublethal concentrations, pest species, and others. In this study, the sublethal effects of sulfoxaflor and acetamiprid on A. gossypii were compared using two field-collected populations. The results show that sulfoxaflor was more toxic than acetamiprid against A. gossypii in both populations, the LC₅₀ concentrations of acetamiprid and sulfoxaflor were 6.35 and 3.26 times higher, respectively, for the Jinghe population than for Yarkant. The LC₂₅ concentration of acetamiprid significantly reduced adult longevity and fecundity in exposed adults (F₀) of the Jinghe population, but it had no significant effects on these factors in Yarkant. Similar inhibitory effects were found in the F₁ and F₂ generations, but the biological traits in the Yarkant population were significantly reduced when the parents (F₀) were exposed to LC₂₅ of acetamiprid, whereas the changes in the Jinghe population were not significant. However, sublethal sulfoxaflor showed a stimulatory effect on A. gossypii in the F₀ and F₁ generation; the adult fecundity and longevity of the F₀ generation were significantly higher in Jinghe, while the biological traits of the F₁ generation were obviously higher in Yarkant. In the F₂ generation, the r and λ were significantly higher in Jinghe; meanwhile, these biological traits were reduced in Yarkant. These results indicate that sulfoxaflor and acetamiprid had different sublethal effects on A. gossypii that varied by generation. In addition, we speculate that the genetic background and the resistance levels of A. gossypii may also influence the sublethal effects. Our findings are useful for assessing the overall effects of sulfoxaflor and acetamiprid on A. gossypii.

Cotton aphids are the primary pests that adversely affect cotton growth, and they also transmit a variety of viral diseases, seriously threatening cotton yield and quality. Although the traditional remote sensing method with a single data source improves the monitoring efficiency to a certain extent, it has limitations with regard to reflecting the complex distribution characteristics of aphid pests and accurate identification. Accordingly, there is a pressing need for efficient and high-precision UAV remote sensing technology for effective identification and localization. To address the above problems, this study began by presenting a fusion of two kinds of images, namely panchromatic and multispectral images, using Gram–Schmidt image fusion technique to extract multiple vegetation indices and analyze their correlation with aphid damage indices. After fusing the panchromatic and multispectral images, the correlation between vegetation indices and aphid infestation degree was significantly improved, which could more accurately reflect the spatial distribution characteristics of aphid infestation. Subsequently, these machine learning techniques were applied for modeling and evaluation of the performance of multispectral and fused image data. The results of the validation revealed that the GBDT (Gradient-Boosting Decision Tree) model for GLI, RVI, DVI, and SAVI vegetation indices based on the fused data performed the best, with an estimation accuracy of R² of 0.88 and an RMSE of 0.0918, which was obviously better than that of the other five models, and that the monitoring method of combining fusion of panchromatic and multispectral imagery with the accuracy and efficiency of the GBDT model were noticeably higher than those of single multispectral imaging. The fused panchromatic and multispectral images combined with the GBDT model significantly outperformed the single multispectral image in terms of precision and efficiency. In conclusion, this study demonstrated the effectiveness of image fusion combined with GBDT modeling in cotton aphid pest monitoring.

Thrips pests have become an increasing concern in cotton fields in Xinjiang. Frankliniella intonsa is the primary thrips species during the flowering and boll stages, causing boll stiffening or cracking. However, limited studies have been conducted on controlling F. intonsa. In this study, using a leaf-tube residue method, we evaluated the susceptibility of F. intonsa field populations to three insecticides (spinetoram, imidacloprid, and acetamiprid) collected from different geographical sites across major cotton planting areas in Xinjiang. The results showed that F. intonsa populations exhibited very high susceptibility to spinetoram, ranging from 0.003 mg L⁻¹ in the Shihezi population to 0.036 mg L⁻¹ in the Korla population. The susceptibility of F. intonsa to imidacloprid and acetamiprid varied considerably among different field populations, with the relative resistance of 33.00 and 25.71, respectively. Reduced susceptibility to all three insecticides was detected in the Korla and Manasi populations, highlighting the importance of implementing effective resistance management and alternative control strategies. These findings provide valuable information for the appropriate control of F. intonsa in Xinjiang.

Chrysopa pallens Stephens (Neuroptera: Chrysopidae) is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram at low concentrations (LC₂₀), on C. pallens when exposed via consumption of contaminated prey, assessing impacts on its development and predatory function. C. pallens is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram (LC₂₀) on the developmental performance and predatory capacity of C. pallens. Leaf-dipping bioassays were used to assess the toxicity of imidacloprid and nitenpyram to Aphis gossypii Glover (Hemiptera: Aphididae). Age-stage, two-sex life table analysis was conducted to evaluate their subsequent effects on the life history traits and predation performance of C. pallens. Imidacloprid was more toxic to A. gossypii than nitenpyram. Sublethal exposure marginally prolonged larval development, but the effect was not statistically significant. Both insecticides significantly extended the pupal stage, with nitenpyram inducing a greater delay. Imidacloprid markedly increased adult longevity, and both compounds significantly reduced female fecundity. Imidacloprid also suppress predatory behavior more potently, decreasing daily adult consumption and reducing first-instar attack rates by approximately 30%. Although all treatments followed a Holling type II functional response, both insecticides increased handling time and reduced searching efficiency. Overall, imidacloprid primarily inhibited predatory performance, whereas nitenpyram more strongly prolonged development and reduced critical population growth parameters. These findings provide essential evidence for ecological risk assessment and for refining the incorporation of natural enemies into cotton integrated pest management (IPM) strategies.

The increasing resistance in Aphis gossypii field populations to sulfoxaflor and many different types of insecticides represents a significant challenge in protecting cotton production in China. Although resistant pests were able to regain their susceptibility to insecticides after the reduction in insecticide applications, some of their biological parameters remained different from susceptible strains. The resistance to sulfoxaflor was unstable in A. gossypii after the loss of selective pressure. The strain with declined resistance (Sul-D) (RR = 1.11-fold) restored its susceptibility to sulfoxaflor, acetamiprid, and imidacloprid after the sulfoxaflor-resistant (Sul-R) (RR = 51.57-fold) was maintained without insecticide pressure for 22 generations. Sul-R had a relative fitness of 0.87, and the Sul-D strain still had a relative fitness of 0.84, even if its susceptibility to sulfoxaflor was restored. Compared with the susceptible strain (Sus), the Sul-R and Sul-D strains became more active in searching for appropriate feeding positions because they generated more intercellular apoplastic stylar pathway events (C). However, the phloem-feeding ability was reduced in the Sul-R and Sul-D strains, as shown by the decrease in phloem behavioral parameters, such as phloem salivations (E1), phloem ingestion (E2), and the percentages of E1 and E2. The negative hormesis effect of sulfoxaflor on phloem feeding was observed in susceptible strain but not in Sul-R and Sul-D, as evidenced by the significant decreases in the number of E1, the duration of E1 and E2, and the percentage of E1 and E2 in the Sus strain. Sulfoxaflor resistance was unstable in A. gossypii, and there was still a fitness cost to A. gossypii after recovering susceptibility to sulfoxaflor. The phloem-feeding ability was reduced in the Sul-R and Sul-D strains compared with the Sus strain, but the negative hormesis effect of sulfoxaflor on phloem feeding was only found in the Sus strain. The outcomes of this study could contribute to a comprehensive risk assessment and provide a basis for developing a better strategy to control A. gossypii.