International Journal of Aquaculture, 2025, Vol.15, No.4, 208-220 http://www.aquapublisher.com/index.php/ija 213 the differences in photoperiod responses in different ecological regions and cultivate water chestnut varieties suitable for different latitudes to avoid adverse phenomena such as premature ripening or late ripening without shepherd's formation, and ensure stable and high yield. 5 New Strategies for Green Prevention and Control of Diseases 5.1 Main types of diseases and pests and epidemic rules There are relatively few types of pests and diseases in water chestnuts, but once they occur, they are often serious harm, which is an important factor in limiting continuous cropping and increasing yield. The main diseases include: water chestnut plague (also known as stalk blight), blight, and powdery powder. In addition, underground pests such as grubs can also chew on bulbs to cause wounds (Zhu et al., 2014). Generally speaking, water chestnut pests have the characteristics of "the main transmission of soil is the first, the second transmission of qi is the second, and the underground pests are hidden and the occurrence is concealed." Among them, blight bacteria can survive in the soil for many years, which is the biggest obstacle to continuous cropping; while water chestnut plague is mostly caused by bacteria in long-distance airflow zones, and may have a cross-infection relationship with crop pathogens such as rice. In terms of climate, diseases occur more severely in years with high temperature and high humidity. Traditional prevention and control relies on chemical pesticides, but long-term single use of drugs can easily lead to bacterial resistance and pesticide residue problems. In recent years, with people paying attention to food safety and ecological environment, water chestnut pest control is developing towards green prevention and control (Zhu et al., 2016). 5.2 Application of biopesticides and plant extracts In order to reduce the use of chemical pesticides, various places have gradually introduced efficient and low-toxic biopesticides and plant-source preparations in the prevention and control of water chestnut diseases and pests: mycotoxins and bio-drug agents, plant-source pesticides, natural antioxidants, and natural insect use. It should be pointed out that the effect of biological pesticides is relatively slow and usually needs to be combined with agricultural prevention and control and physical prevention and control to maximize their effectiveness. However, with the development of plant-source preparation purification technology and biofermentation preparations, its prevention and treatment effect and stability are constantly improving. For example, organic planting bases have successfully used mixed spraying of matrine and Bt (Bacillus thuringiensis) to replace chemical pesticides to control borers, with an effective prevention of more than 70%. The application of biopesticides and plant extracts (Li et al., 2022) not only reduces the risk of pesticide residues, but also helps to delay pest resistance and protect the agricultural ecological environment. It is an important direction for green prevention and control of water chestnut pests. 5.3 Rice rotation and ecological regulation technology In response to the problems of continuous cropping of water chestnuts and disease and insect circulation, crop rotation and ecological regulation have proven to be simple and effective strategies: Rice-water chestnut crop rotation: Promote the "early rice+water chestnut" or "one-season rice+water chestnut" crop rotation model in the southern double-season rice areas. Rice and water chestnuts are mutually stubborn, which not only makes full use of the solar and thermal resources of paddy fields, but also breaks the disease and insect cycle. The promotion data of Shaodong County Agriculture Bureau in 2015 showed that in the high-incidence zone of Jiangxi, the prevention effect of water chestnut wilt can reach 34%~41%, while water chestnut plague has interspecies hosts due to bacteria, which can be weakened by crop rotation but is difficult to completely control. Combination of ecological breeding and breeding: In fields with water source conditions, farmers try to apply comprehensive breeding experience of rice fields to water chestnut fields, such as the variant of the rice and shrimp co-cultivation model - "water chestnut-crawfish co-cultivation". Dig up the trenches in the water chestnut planting ditch to raise shrimps, and use crayfish to feed the weeds and some pests in the field. At the same time, the shrimp manure provides water chestnuts with organic fertilizer to achieve ecological circulation. For example, in some water chestnut fields in Guangdong, loaches are raised, so that the loaches loosen the soil, eat grub larvae, and reduce the harm of underground pests.
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