The symptoms are also called melasma. Occurred mainly in 1-2 true leaf stage, injurious to the cotyledons and true leaves. Cotyledons mainly develop dark green mold layer at the unexpanded bond site or at the damage of the crust. The cotyledon was flattened, diseased, and had a small round spot of reddish-brown color, which expanded into an irregular shape to a nearly circular brown spot, and some were not obvious. When the humidity is high, the dark green mold layer grows on the lesions, and the number of lesions on each of the severe leaves is as large as several tens, resulting in the cotyledons off-focus. Symptoms of true leaf disease are similar to those on the cotyledon, but the lesions are large and there are purple-red lesions around. Injury occurred when the disease, the shape of the lesion is irregular, there are no purple edges around the spots. The stems or petioles of the seedlings are infected to produce oblong brown concave spots, causing the leaves to fall and the seedlings to die.
The pathogen Alternaria macrospora Zimm, called Alternaria alternata, A. tenuissima Wiltsh called Alternaria alternata and A. gossypina (Thum.) Hopk called Alternaria solani, are all fungi of the subphylum Aspergillus. Its pathogenicity is different, the large chain package has strong pathogenicity, can directly invade, and produces larger rosy spots on the cotyledon or true leaves. The conidiophores of this bacterium were more than solitary or 4-9 bunches, slightly curved, and the base expanded, light brown to dark brown. Conidiophores clublike, yellow-brown or dark brown, with 6-10 transversities, 3-30 mediastinums. Alternaria spp. has weak pathogenicity and is often invaded by other parasites or invaded when there is a wound. Conidiophores have fewer branches, brownish brown, conidiophores, stringing, 1-9 transects, 0-6 mediastinals. The optimum growth temperature of pathogenic bacteria is 27-30°C. Above 37°C and below 0°C, it cannot grow. In the cotton field temperature of 27-33 °C disease, 25 °C optimum, high humidity, easy to invade, to adapt to pH 2-10, wherein the pH5 optimum.
Transmission Pathways and Pathogenic Conditions The pathogenic bacteria are overwintering on mycelium and conidia on diseased leaves, diseased stems or cottonseed fleece. The rate of cottonseed feeding is as high as 47.5%-84%, especially on the seed husks, and the endosperm is also carried. After the sowing of cottonseed, the conidia on the diseased leaves and cottonseeds are transmitted by gas or rain spattering, and they penetrate directly from the wound. In early spring, the temperature is low and the humidity is high. When the temperature suddenly drops from 20°C to 6-10°C, there is rainfall, and the relative humidity is higher than 75%. In the late growth stage of cotton, the plants are weak, and in case of autumn rain, the onset of peaks may also occur.
Control methods (1) The cotton field must be finely soil-prepared and the seeds must be carefully selected to improve the quality of sowing. (2) Promote the use of mulching, which can increase the incidence of reduced temperature at the seedling stage. (3) Chemical seed dressing. Seed dressing with 65% seed weight of 50% carbendazim WP or 40% seed dressing double wettable powder. It can also be soaked in a 061% carbendazim solution. Carbofuran can also be used with 50% carbendazim in a weight ratio of 1:0.5, a small amount of polyvinyl alcohol adhesive is added, cotton seed coating agent is prepared, and the compost produced is treated with a seed coating agent having a cotton seed weight of 1%. Diligent cultivator, timely pruning and picking up leaves, draining water in time after rain, and preventing moisture from staying, can reduce the incidence. (5) Spray 70% mancozeb WP 500 times or 75% chlorothalonil suspension 500 times, 80% WP wettable powder 600 times, and 50% lime sulfur 400 times .
Baiju Price,Baijiu Chinese Drink,Chinese Baijiu For Sale,Chinese Rice Wine Baijiu
Shan Dong Kao Shang wine industry Co.,Ltd , https://www.ksbaijiu.com