What are the methods for controlling cowpea rust in autumn?
How do you control rust when growing cowpeas in autumn? Here is an introduction to the control methods. The growing environment for autumn-planted cowpeas has high temperatures and relatively high rainfall, and in addition the inoculum (urediniospores) left behind in the field from spring-planted cowpeas is abundant. Therefore, autumn-planted cowpeas are prone to rust, and farmers should carry out integrated control early. 1. Main symptoms: the whole...
How do you control rust when growing cowpeas in autumn? Here is an introduction to the control methods
The growing environment for autumn-planted cowpeas has high temperatures and relatively high rainfall, and in addition the inoculum (urediniospores) left behind in the field from spring-planted cowpeas is abundant. Therefore, autumn-planted cowpeas are prone to rust, and farmers should carry out integrated control early.
I. Main symptoms: Cowpeas can be infected by the pathogen throughout the entire growing period, but resistance weakens and susceptibility increases from the beginning of flowering to podding. The disease mainly attacks the leaves; in the early stage of the disease, scattered chlorotic yellow-white spots appear on the underside of the leaves, and the spots gradually increase until they densely cover the entire leaf. On the corresponding upper surface of the lesions, yellowish-brown slightly raised scab-like spots, namely uredinia, form; after the uredinia rupture, large numbers of urediniospores are released, and on old leaves in the late growth stage black telia sometimes form. The leaves wither and yellow and drop off, the plant is stunted, the pods are few and small, the growth period is shortened, and finally the plant withers, becomes thin and dies.
II. Pathogen: it belongs to the Basidiomycota, genus Uromyces. The source of infection is the diseased residues of spring-planted cowpeas or the uredinia left in the field; the urediniospores germinate and produce germ tubes, which invade the host through the stomata. At 18-25°C, when air humidity is high or fog and dew are heavy, and when there is a water droplet film on the host surface, the urediniospores germinate and invade the host most easily; the diseased plants then spread the urediniospores through air currents, insects, and humans and livestock among plants in the field, causing frequent re-infection, and the telia produced in turn become the primary infection source for leguminous crops planted the following spring.
III. Control methods: integrated control measures based on strengthening the management of soil, seed, fertilizer and water, supplemented by timely spraying for control.
1. Remove diseased residues to reduce the source of infection: after harvesting spring-planted cowpeas, collect the residual plants and dead seedlings and burn them to reduce the source of infection.
2. Seed selection and site selection: ① Seed selection and planting: choose disease-resistant varieties, such as Suifeng No. 8 and Zaofeng No. 3, and grow them on raised beds, preferably in double rows or single rows, as this makes it easy to drain away standing water and improves ventilation, which is unfavorable for the landing and invasion of urediniospores. ② Site selection: it is best to choose a field whose previous crop was a grass-family crop, and not to choose a field whose previous crop was a leguminous crop or peanut. This can avoid direct attack by the rust fungus.
3. Rational fertilization: apply sufficient base fertilizer, apply topdressing early, and increase the application of phosphorus and potassium fertilizers, so that root nodule activity is enhanced, the plants grow sturdy, the leaves are dark green and thick, and disease resistance is increased.
4. Timely pesticide application for control: apply pesticide in time at the early stage of disease onset. The agents can be 50% triadimefon at 600-800 times dilution, or 50% sulfur suspension concentrate at 500-600 times dilution, or 70% thiophanate-methyl at 800-1000 times dilution, sprayed on. Spray once every 8-10 days, for 2-3 consecutive sprays.
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