How to control pests and diseases during the cotton sowing and seedling-raising period?
The cotton sowing and seedling-raising period is an important part of cotton production. According to the municipal meteorological observatory forecast, in the spring of 2008 (March to April) precipitation will be normal to slightly low, with 200-250 mm in the Dabie Mountains and 240-290 mm in other areas. The average spring temperature will be close to normal, with large temperature fluctuations and frequent cold air activity; late spring cold spells may occur. This is relatively favorable for the occurrence of cotton spider mites and cotton thrips. Because of the large temperature fluctuations, cotton seedling growth is unfavorable, seedling resistance is reduced, and this is also favorable for the occurrence of cotton seedling diseases. To ensure full emergence after sowing and early growth of strong seedlings, the following control measures are proposed:
I. Control of cotton seedling diseases
1. Choose a good seedbed. For the seedbed soil of the seedling-raising bed, it is best to use imported soil and apply thoroughly decomposed farmyard manure, so as to ensure the nutrient soil for the pots does not contain pathogens such as Fusarium and Verticillium wilt, and use large pots for seedling raising to ensure strong growth of cotton seedlings in the seedbed. If soil from cotton planted the previous year is used to make pots, choose a place without diseased spots to arrange the pots.
2. Sun the seed before sowing. Sun the seeds for 2-3 days before sowing to kill some of the pathogens carried on the seeds, enhance seed vigor, promote after-ripening of the seeds, and increase the germination rate and germination vigor.
3. Reasonable crop rotation. Where conditions permit, it is best to rotate cotton with gramineous crops to reduce the number of pathogens in the soil, lower the incidence of cotton seedling diseases, and benefit cotton seedling growth.
4. Sow at the right time. According to the climate characteristics of our city, for nutrient-pot seedling raising, choose sunny and warm weather in early to mid-April for sowing.
5. Chemical control. When raising seedlings, mix hymexazol or carbendazim or dexon into the seedbed soil to disinfect the seedbed. After cotton seedlings emerge completely, especially at the 1-leaf stage, if low-temperature and rainy weather occurs, cotton seedling diseases may become epidemic. In such cases, drain water promptly to prevent waterlogging, apply a light seedling-promoting fertilizer early, and apply pesticide for control. The control agents are yizailing emulsifiable concentrate, or baoxianke emulsifiable concentrate, or fulvic acid salt wettable powder, or cotton Fusarium wilt powder wettable powder, or Lvbang 98 wettable powder.
6. Fine land preparation. Before transplanting, loosen the soil 1-2 times in the field after the previous crop is removed or between the rows of the previous crop, so that the rows are level, the soil is fine, and the weeds are clean. For lower-lying cotton fields, deep furrows and high beds should be used. When the soil is not very compacted, no-till transplanting with deep plowing can be used.
II. Control of insect pests in the seedbed. The main insect pests in the seedbed are cotton spider mites, plant bugs and cotton thrips. For plant bugs, use fipronil, acephate, chlorpyrifos and other pesticides for control. For cotton spider mites, when the rate of mite-infested plants is below 15%, treat only the affected plants; when it exceeds 15%, treat the whole field. The control agents are pyridaben, abamectin, propargite-type acaricides and their mixtures. For cotton thrips, when the damaged plant rate before transplanting reaches 5%, use acetamiprid, carbosulfan, high-content imidacloprid and other pesticides for control. Before transplanting, remove headless seedlings and choose healthy seedlings for transplanting.
III. Control of snails in cotton fields. Under climatic conditions with abundant rain and continuous overcast and rainy weather, snail damage is likely to occur at the cotton seedling stage and even the bud stage, especially with a large occurrence in May. When snails occur, apply wokexing or wote by broadcasting.
IV. Weed control in cotton fields. Adopt a combination of intertillage weeding and chemical weeding. It is recommended to reduce the number of applications of non-selective herbicides as much as possible, giving priority to intertillage weeding to protect the physical and chemical properties of the cotton field soil. Chemical weeding: after cotton emerges, at the 2-3 leaf stage of weeds, spray with gaicaoling, quizalofop-p-ethyl, haloxyfop-R-methyl and the like. For cotton fields where the previous crop was rapeseed, if a non-selective herbicide is used for weed control, after the rapeseed harvest, choose 10% glyphosate aqueous solution or 41% Roundup aqueous solution, dilute with 50 kg of water and spray, then transplant cotton seedlings one week later; or choose 20% gramoxone aqueous solution, dilute with 50 kg of water and spray, then transplant cotton seedlings 2 days later.