Cotton Genomics and Genetics 2025, Vol.16, No.1, 29-38 http://cropscipublisher.com/index.php/cgg 30 2 Major Cotton Diseases and Insect Pests 2.1 Overview of significant cotton pathogens Cotton is not always attacked by large-scale diseases, but once it encounters suitable climatic conditions, the situation often becomes difficult quickly. For example, in recent years, with the rise in temperature and changes in humidity, some pathogens that were originally well controlled have begun to break out frequently and spread quickly. Cotton is actually threatened by many things, not just a certain type of pathogen, but also fungi, bacteria, viruses, and nematodes. They often do not appear alone, but "go into battle" together. Verticillium wilt and Fusarium wilt are particularly typical. The former is caused by Verticillium dahliae, and the latter is mainly related to Fusarium oxysporum. Once the yield is affected, the loss is immediately apparent (McGarry et al., 2024). And like bacterial wilt, there are some diseases that occur on the leaves. Although they are not necessarily fatal, they will slow down the growth and reduce the fiber quality (Manavalan, 2022). As for viruses and nematodes, they may not kill cotton directly, but they are very troublesome to control and are prone to recurrence. If climate factors are not taken into account, it may be okay, but the reality is that pathogens are becoming more and more "adapted to the environment" and more and more difficult to deal with. 2.2 Key insect pests of cotton Cotton can be attacked by many pests, some of which are piercing-sucking pests and some are chewing pests, and they can cause great losses. Common piercing-sucking pests include whitefly (Bemisia tabaci), big leaf aphid (Amrasca biguttula biguttula), thrips (Thrips tabaci) and cotton aphid (Aphis gossypii) (Sonalkar, 2020). There are also many chewing pests, especially cotton bollworms, such as pink bollworm (Pectinophora gossypiella), spotted bollworm (Earias insulana and E. vitelli) and American bollworm (Helicoverpa armigera), which are also very harmful to cotton (Razzaq et al., 2023). Although planting Bt cotton can control some bollworms, some pests are not affected by Bt cotton, especially piercing-sucking pests, which have increased in number (Figure 1) (Minorsky, 2018). Figure 1 Changes in pest-community interactions due to Bt cotton and Bt toxins. ★ Plant debrises include defoliation, pollen falling, and sqare and boll shedding (Adopted firom Razzaq et al., 2023)
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