Control of cotton seedling diseases in spring

In recent years, due to the low temperature in spring, the seedling disease in direct seeding cotton field is serious, resulting in a large number of dead seedlings in cotton field. In order to improve the economic benefits of cotton farmers and reduce the losses caused by diseases, the symptoms and control methods of several diseases in cotton seedling stage are introduced as follows:

I. symptoms of damage to cotton seedlings

1. Anthrax: both leaves and stems can occur. After the seedlings were damaged, reddish-brown fusiform spots appeared at the base of the stem, which were longitudinally cracked. In severe cases, the disease spots were enlarged brown, blackened and rotted, resulting in the death of the seedlings. When the weather is wet, the disease spot produces orange sticky substance. When the leaf is sick, a semicircular brown disease spot occurs at the edge of the leaf. When the weather is dry, the edge of the disease spot is crimson, and when the leaf is serious, the leaf wilts and falls off.

two。 Blight: generally speaking, it is most likely to occur half a month after cotton seedlings are unearthed. The damaged part was at the base of the stem of the cotton seedling near the ground, the disease spot changed from yellow-brown to dark brown, and gradually sunken and rotted downwards, and the cotton seedling fell down and died due to the shrinkage of the stem.

3. Brown spot: the injured leaves at first appear needle-sized purplish red spots, and then the disease spots expand into yellowish brown, the edge of the purplish red, slightly raised, the following scattered small black spots. The diseased tissue is easy to fall off and appear to be perforated. Serious damage can cause leaves to fall early.

4. Ring disease: mainly harms leaves, sometimes stems, petioles and cotton bolls. The red or light brown dots that began to appear when the leaves were damaged gradually expanded into a nearly round shape, with concentric patterns on the brown, and a black mildew layer on the spots when the weather was wet. In serious cases, the leaves can wither and fall off, and even the whole plant will die.

II. Prevention and control of diseases at seedling stage

The pathogens of various diseases in the seedling stage mainly spend the winter on the cotton seed, soil and the remains of diseased plants, and infect the seedlings when the cotton is sown to the appearance of true leaves in the next year. In order to ensure that Miaoquan and Miao are strong, the main measures are as follows:

1. Agricultural prevention and control

(1) select seeds. On the basis of getting rid of tender seeds, diseased seeds, insect seeds and light seeds, full seeds were selected and planted in the sun for 3-5 days, which could obviously increase the emergence rate and enhance the disease resistance of cotton seedlings.

(2) fine soil preparation. Leveling the land ahead of time, generally turning 25 cm to 30 cm deep, applying sufficient organic fertilizer and base fertilizer (diammonium 15 kg, potassium sulfate 15 kg), timely late sowing (5 cm ground temperature is stable above 10 ℃). Prevent sowing too early, due to low ground temperature, leading to rotten seeds and diseased seedlings.

(3) strengthen field management. After the cotton seedlings are unearthed, loosen the soil in time, increase the soil temperature, reduce the soil moisture and reduce the chance of pathogen infection. Early seedlings, fixed seedlings, cultivate strong seedlings.

(4) the plots with serious occurrence of blight and brown spot should be rotated reasonably with corn, corn and so on.

two。 Chemical control: 25% carbendazim can be used during sowing time, 1 kg for every 50 kg of cottonseed, and evenly mixed 5-7 days before sowing. At the seedling stage, the affected plots were sprayed with 70% methyl topiramate 800 × 1000 times or 50% carbendazim wettable powder 500 times 800 times, once in 5 days and 3 times in succession, and the effect was significant.