Field Crop 2025, Vol.8, No.6, 274-283 http://cropscipublisher.com/index.php/fc 277 3 Biological Control as a Sustainable Strategy 3.1 Types of biological control agents used in cotton In the cotton fields, there are actually quite a few "biological weapons" that can be put to good use. The earliest and most widely used were fungi, such as Beauveria bassiana and Metarhizium rileyi, which could infect lepidoptera larvae and sucking pests, causing the pests to "fall ill" themselves (Malinga and Laing, 2021). Bacterial preparations are also common. For instance, Bacillus velezensis (Bt) has almost become synonymous with insect control. There are also some rhizogenic bacteria (PGPR), such as Bacillus Velezensis, which have both pest control and nematode inhibition functions. In addition, viruses (such as nuclear polyhedral virus) and microsporidia can also exert pathogenic effects against specific pests, such as cotton bollworms (Malinga and Laing, 2022). Of course, don't forget the natural enemies. Ladybugs, lacewings, predatory stink bugs and various parasitic wasps (such as Trichogramma and wasp) are all quietly "helping" in the cotton fields, playing a natural control role in the pest population. 3.2 Mechanisms of pest suppression These biological control measures do not function through a single mechanism. Fungi and bacteria infect the surface or interior of pests in a relatively direct way, inactivating the pests through toxin or tissue infection (Dannon et al., 2020). The role of predators and parasitic wasps is more like that of "natural police". They prey on or parasitize pests, gradually reducing the population size. Some rhizosphere bacteria take a different path: they do not directly kill insects but induce the cotton's own defense response, making the plant more resistant. There is another indirect way, by adjusting the field habitat, such as associated planting or intercropping, to attract more natural enemies to participate and form an ecological protective barrier (Cui et al., 2023). 3.3 Advantages of biological control The benefits of biological control are often not limited to one aspect. The most obvious is that less chemical pesticides can be used, which not only reduces the environmental burden but also slows down the rate at which pests develop resistance (Bordini et al., 2021). Its "selectivity" is also a major advantage. Unlike broad-spectrum pesticides that are "one-size-fits-all", moderate use can preserve the population of natural enemies and maintain ecological balance (Xue et al., 2022). In terms of safety, biological control agents are milder to humans, animals and non-target organisms. Most importantly, it can be combined with other management methods to become the most stable part of the Integrated Pest Management (IPM) system, providing a more sustainable path for cotton cultivation. 4 Companion Planting for Pest Management 4.1 Functional roles of companion plants In cotton fields, companion plants are often regarded as a kind of "natural assistant". Some plants can "lure away" pests, playing a role in attracting them. When pests are drawn to these attracting crops, farmers can deal with them in more concentrated areas (Annells et al., 2003). There are also some plants that are just the opposite. The odors they release can mask the odor signal of cotton, causing pests such as aphids to get lost and fail to find their targets (Blassioli-Moraes et al., 2022). In addition, companion plants also provide food and hiding places for beneficial insects, such as pollen, nectar or shady leaf clusters, thereby attracting and maintaining the number of natural enemies. There is another situation where cover crops like black velvet beans have little attraction to major pests. Pests tend to avoid these areas, and thus cotton becomes "safe" instead. 4.2 Enhancement of field biodiversity Cotton has been planted for several consecutive years, and the fields are often "unusually quiet". With more pests and fewer natural enemies, the ecosystem becomes monotonous. However, once companion plants are introduced, this situation begins to loosen. When different crops are mixed together, the structure of the field becomes more complex. Natural enemies have places to hide and forage, and the number of predators and parasitic wasps also increases accordingly (De Araujo et al., 2024). The familiar habitats of pests have been disrupted, and their reproductive rhythms have also been disturbed. It is not so easy for them to break out (Yousefi et al., 2024).
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