Recently, many provinces in the country have sustained rainfall weather, long rainy season, heavy rainfall intensity, especially in the south of the flood disaster, such climate conditions for the occurrence of crop diseases created favorable conditions。Experts remind that after floods, it is necessary to focus on the prevention and control of rice blast, corn small spot disease, grape downy mildew and other diseases, actively respond to and actively prevent, and maximize the control of crop diseases prone to rain。

  Rice blast and sheath blight

  Since the beginning of July, many areas in southern China have been hit by floods, which has greatly affected agricultural production。The long-term heavy rainfall makes the situation of rice diseases and pests severe, plant protection departments remind that the high temperature and rainy weather is conducive to the occurrence of bacterial diseases of crops, and the prevention and control of rice blast, leaf blight and other diseases should be focused on after flooding, and the detection and reporting should be strengthened to achieve early detection, early medication and early blockade。

  Rice blast is an important disease in rice production. In recent years, with the expansion of planting area and the accumulation of bacterial sources, the occurrence of leaf blast in the middle and early stage of rice has increased。This year, the rain came early, the rainy season is more frequent, and the temperature is not high, such climatic conditions are easy to cause the occurrence and epidemic of rice blast。In July and August, the eastern southwest, Jianghan, Jianghuai and southern Northeast will have more rainfall, which is conducive to the occurrence and prevalence of rice blast, according to the National Agricultural Technology Center Disease Survey and Pest Report Office。Zhao Zhonghua, a researcher at the prevention and Control office of the National Agricultural Technology Center, said that rainy days and high temperatures and lack of sunshine create favorable conditions for the occurrence of crop diseases, and rice with a short growth period and poor disease resistance is prone to rice blast。

  For example, Jiujiang City, Jiangxi Province, which is more seriously affected by floods, the plant protection department issued a warning for the prevention and control of rice diseases and insect pests after the disaster. The rainy weather will continue in the near stage, which is very favorable for the occurrence of leaf rice blast, dry blight, thin stripe disease, bacterial base rot of flooded rice fields and other diseases, which is easy to break out and cause disaster。It is required to grasp the two key periods from tiller to booting stage of middle rice and before the transplanting of late rice seedlings, and make every efforts to prevent and control major diseases and pests such as "double migration" pests, borers, leaf plague, southern rice black stripe dwarf disease and dry blight, and strengthen the prevention and control guidance of bacterial diseases in flood areas to promote the recovery of stricken rice。It is recommended to choose 75% tricyclazole WG30~ 50g/mu or 40% EC100~ 150g/mu for leaf blast control，To prevent sheath wilt, 1% Shenazinomycin SC50~75 ml/mu or 20% jinggangmycin 50~75 g/mu were selected，For the prevention of fine stripe disease and bacterial base rot, 20% thiothiazide copper SC or 20% bacteriotoxin AS100~150 grams per mu。In order to overcome the contradiction that it is easy to be washed by rain after taking medicine in rainy weather, organic silicon or "stimulating" synergist is added to the spray medicine solution to ensure the prevention and control effect。

Hunan is also one of the areas affected by heavy rainfall. Tang Huilian, deputy head of Hunan Plant Protection Station, suggested that rice and other crops affected by mechanical damage should be prevented from bacterial diseases such as white leaf blight after the disaster。It is recommended to use brassinolide, soil conditioner, propithiazole and other agents to improve crop stress resistance and root development and reduce the risk of large-scale rice blast。

  Maize small spot disease, rust

  Among the three factors of disease occurrence, climatic conditions play an important role。In particular, some diseases spread by wind and rain, when encountering suitable climatic conditions, the spores of bacteria will invade and cause the disease。This is the case with corn patch。The rainy weather conditions this year will aggravate the occurrence of maize small spot disease。This kind of disease has a short course and fast spread. Once it occurs, corn leaves will spread rapidly from bottom to top, resulting in premature leaf death, affecting the formation of strong stalks and large ears of corn, and greatly affecting the yield of corn。In the prevention and control strategy and technology, it is necessary to replace the drug varieties, and change to 30% methyl-C (methyclozole, propiconazole compound), to achieve the purpose of one-time medication, treating the small spot disease, and treating the blight disease and rust disease。For the diseased fields, 30~40 ml of 30% methamphetamine was applied to corn leaf surface spray per mu。

Maize stem bacterial base rot is also one of the diseases affected by wind and rain, which generally occurs in the middle and late period of maize, and its degree of occurrence varies greatly between years and varieties under climatic conditions。The symptoms in the field are mainly harmful to corn stems, causing rot and odor。Control can be 50% chlorobromoisocyanuric acid 600x spray。                     

  Citrus canker

  Citrus fruit trees are most susceptible to canker disease in summer, especially after typhoon rains, canker spots will appear on the leaves, branches and fruits, resulting in yellow leaves, fallen leaves, branches dry and fruit drop。

  At present, attention should be paid to the prevention and control of citrus canker, which must be sprayed every 15 to 20 days with 600 times 20% thiazide copper solution, or 1500 times 33.5% quinoline copper solution, or 600 times 30% thixene copper solution for prevention。When the autumn shoots have just sprouted, spread the leaves and turned green, each leaf surface must be sprayed 800 times 1.8% octamine acetic acid brine solution, or 5000 times 72% agricultural streptomycin sulfate solution, or 1500 times 46.1% copper hydroxide solution for prevention。Before and after each typhoon, each leaf surface must be sprayed once 1500 times 35% copper oxychloride solution, or 800 times 50% chlorobromoisocyanuric acid solution for prevention。In this way, citrus branches, leaves and fruits are protected from anthrax。

另外，Pay attention to check，Canker spots were found on branches, leaves and fruits，It is necessary to continuously spray 2 to 3 times 1000 times 47% spring Lei Wang copper solution，Or 1000 times 25% leaf cumazole aqueous solution for prevention and treatment，Spray every 7 to 10 days，Evenly wet all branches, leaves, and fruits inside and outside the crown。If you can add 0 to the liquid medicine.2%~0.3% potassium dihydrogen phosphate aqueous solution with spray, the effect is better, not only can strengthen the efficacy of sterilization, improve the control effect, but also can enhance the resistance to disease, accelerate the normal growth of the diseased tissue, but also can supplement nutrition from the leaf surface, improve the quality of the fruit and fruit yield, improve the quality。

  Vegetable disease

  Cataplexy in vegetable seedling stage

  After the rain, it is the season for planting and breeding vegetables such as Chinese cabbage, cabbage and green pepper after autumn。The condition of high temperature and high humidity will aggravate the occurrence of many vegetable seedling cataplasis, which can destroy the seedlings and delay the best planting time of vegetables if the control is not good。The control method should be 69% enyl · manganese zinc 800 times liquid spray at the seedling stage of vegetables。At the same time, it is necessary to control the watering of the seedling bed after emergence to prevent the occurrence of diseases caused by artificial increase in humidity。

  Blight of green pepper in autumn

  The blight of autumn pepper occurred seriously in the seedling stage。Light is missing trees and ridges, heavy is destroyed seedlings destroyed shed。The disease has a short course, rapid onset and more dead seedlings under high temperature and humidity conditions。The bacteria invaded from the stem of the young base of the green pepper。The best control method is planting and watering。After the planting of autumn pepper, the roots were poured with 69% enoyl · manganese zinc 800 times the liquid, 300~350 kg of liquid per mu。For large planting area and inconvenient water source, 35% enyl and frosturea cyanide can be sprayed 800 times on the roots。Of course, the prevention and control of green pepper disease should pay more attention to the coordination of agricultural measures, mainly to improve the field water system, keep the field without water, do not flood irrigation, thus worsening the conditions of disease occurrence。

  Chinese cabbage downy mildew, soft rot

Downy mildew and soft rot of Chinese cabbage are two kinds of diseases with different pathogens and serious harm。Downy mildew is a low-grade fungus. In the field, the symptoms are that the growth starts from the lower leaves in the middle and late stages, the front of the leaves produces a small yellow spot, and the back of the yellow spot has a mildew layer, and it expands rapidly from the bottom to the top under rainy conditions。Soft rot is a kind of bacterial disease, which occurs seriously under high temperature and rainy conditions in the middle and late period of Chinese cabbage。The typical symptoms in the field are putrefaction and odors。After years of production practice, although the pathogens of these two diseases are different, the prevention and control can choose an agent at the same time and simultaneously use 50% chlorobromoisocyanuric acid 500 times spray。In the early stage of disease prevention, it is best to use a motorized mist machine to hit the back and root of Chinese cabbage leaves。The key point of prevention and control is to achieve early prevention and early treatment on the basis of the selection of appropriate drugs。

  Grape downy mildew, white rot

  Since the middle of June this year, heavy rains have fallen in various areas, and some orchards have been flooded。The humidity of the vineyards after waterlogging is too large, and the diseases such as downy mildew, grape white rot and grape anthracnose are easy to occur in large numbers。In particular, the occurrence of grape downy mildew is closely related to rain. Continuous and uninterrupted rain brings great difficulty to the prevention and control of grape downy mildew。The grape downy mildew occurred suddenly, spread rapidly, leaves after just two days will spread to the whole garden disease, some people reflected that after two times of medicine, grape downy mildew has been obviously controlled, but a rain will be repeated infection, increasing the difficulty of prevention and control。

  According to the actual situation of the damage, combined with the key points of vineyard management, we should dredge the ditch in the garden in time, discharge the water in the garden, and do a good job of ploughing and loosening the soil, reasonable topdressing, which can be 0.1%~0.Foliar topdressing was performed on 2% potassium dihydrogen phosphate。After the tree recovery, then apply the decomposed organic fertilizer or urea to promote the development of new roots。Take the sundries out of the garden in time and deal with them centrally。Pruning and removal of fallen leaves, diseased branches, diseased fruit, in addition, timely spraying control is also necessary。

  40% enyl morpholine suspension 1500 times + pyrimethil and phenacetoconazole can be used for the whole garden spraying, spraying should be early, comprehensive and meticulous。Spray a protective fungicide such as 250g/L pyrimidin and 50% methylthiobacillam SC within a week for prevention。And according to the actual situation of the occurrence of insect pests in their gardens, appropriate insecticides are selected to prevent and control the breeding and spreading of insect pests。