Causes and prevention methods of pear scab
Experimental results
The control effect of 20% myclobutanil suspension on pear scab is designed. The design test consists of 20% myclobutanil suspension 3000 times solution, 4500 times solution, 6000 times solution, and 12.5% ​​nitrile emulsifiable concentrate: 3000 times solution. The control agent and the water control were treated in five treatments, and the drug was sprayed with a motorized sprayer, sprayed once every 7 days, and sprayed three times.
Basic situation This trial was conducted on June 13th, when the onset of black spot disease occurred. During the test period (June 13 to July 11), the park was not watered or topdressed, with a total rainfall of 7 times and 21.8 mm.
The effect test on the prevention and control of scab on fruit showed that the 20% myclobutanil suspension had better control effect on pear fruit scab. After 7 days of drug investigation, the control effects of 3000 times solution, 4500 times solution and 6000 times solution were 90.1%, 90.1%, and 70.3%, respectively. After 14 days of spraying 3 times, the control effects of each treatment were 100%, 91.0%, and 54.9%, respectively. It can be seen that the concentration of 20% myclobutanil suspension is 3000 times and c4500 times. Effective. Myclobutanil is effective in controlling pear scab.
Pear scab, also known as scab, fog disease, is the most serious disease of pear, shoots, leaves, fruits can be sick, injured after shoots coke orange, yellow fall after leaves victims, victims of epigenetic fruit spots Later, the tortoise pear, the fruit becomes deformed, and the bitterness loses the edible value. In that year, the yield can be reduced by 20-40%, and the output of the second year is affected. According to many years of practice survey, the causes and prevention measures of black spot disease are as follows:
1. Pear scab symptoms Pear scab is the green tissue of pear trees, including bud scales, leaves, petioles, new shoots, fruits, fruit stalks, buds, inflorescences and other parts. In the early stage of the leaf disease, a round, elliptical or irregular yellowish small spot was formed on both sides of the main vein of the leaf back and between the branches, and the boundary was not obvious. After a few days, black mold was formed on the lesion. When the damage is serious, many lesions merge, and the back of the leaves is covered with black mildew, causing fallen leaves. The petiole is damaged, and black and elliptical concave lesions appear on the petiole, resulting in a black mold layer, which is easy to fall early. The veins are damaged and the symptoms are similar to the petiole.
The pear buds are killed, the scales are more hairy, and the mildew layer is formed on the surface at the later stage. When the buds are severe, the bud scales are cracked, and even the oranges die. In the spring of spring, the new shoots sprouted from the buds, and there were pale yellow irregular shaped lesions at the base. Soon the surface was quickly covered with black mold layer, and the diseased part gradually became depressed, cracked and became ulcerated spots.
During the growth period, new shoots are damaged, and lesions are formed on the young branches or the young shoots. The lesion is oval or nearly round, pale yellow, slightly bulging, and there is a black mold layer on the surface. Later, the diseased part is sunken and cracked, forming a sore-like shape.
The fruit was damaged in the early stage, and the fruit surface produced a light brown round disease, which gradually expanded to 5-10 mm, and the surface grew black mold layer, and the growth of the diseased part stopped. As the fruit enlarges, the diseased part gradually sinks, the wood is plugged and cracked. In severe cases, the fruit is deformed, the surface of the fruit is uneven, the flesh of the diseased part is hard, bitter, and the fruit is easy to fall off early. When the fruit grows to the middle and late stages, the black mold layer on the fruit surface lesions is often washed away by the rain. The diseased part is often spoiled by other bacteria, and the pink or grayish white mold grows. The fruit is damaged in the late stage of growth, and there are round or nearly round black lesions of different sizes on the fruit surface. The surface is dry and rough, the mold layer is few, and the fruit is not deformed. Damaged before harvesting, there are pale yellow spots on the fruit surface, the edges are not neat, most of them are awn-like, no mold layer, but after short-term high temperature and high humidity after harvest, the lesions expand rapidly and grow a lot of black. Mild layer.
Second, the incidence of disease Pseudomonas sclerotiorum with conidia and hyphae over the bud scales, diseased leaves, diseased fruit and diseased branches overwinter, the second year of spring when the temperature and humidity are appropriate, the remaining winter subspores and diseased parts formed Conidia, spread by wind and rain, and dyed. After years of field observations, Yunnan Yuxi mainly overwintered the immature ascidian hulls on the leaves, and began to infect from late March to early April of the next year. It takes 14 to 20 days to invade from the germination to the onset. From June to July, the disease is in full bloom, and the disease gradually declines after mid-August. The occurrence of scab is closely related to rainfall. Generally, the incidence of heavy rain is heavy, and the incidence is mild in dry years.
Third, prevention and treatment methods 1, clearing the source: in the late fall and early winter, completely remove the leaves and weeds, collect the diseased fruit, concentrate on burning, combined with winter shears, cut off the diseased dead branches, reduce the winter base of the bacteria.
2. Strengthen the management of orchard: strengthen the management of soil, fertilizer and water, scientifically fertilize water, increase the application of organic fertilizer, improve the ventilation and light transmission conditions of the orchard, and improve the disease resistance of the plant.
3, pesticide fungicide prevention and control: spray 50% mancoamine 400 times before germination, brake dead source. When the diseased shoots or diseased flower clusters and diseased leaves are found in the field, the first spraying is carried out. After that, according to the climate and the incidence, the susceptible varieties are sprayed once every 15 days or so, and a total of 5 to 6 times are sprayed. In combination with other diseases, the selected agents are 1:2～2.5:200～240 times Bordeaux mixture, 50% carbendazim 600～800 times solution, 70% methyl thiophanate 800～1000 times solution, 80% daisen zinc 600 ~800 times liquid, 50% mancoxamine 400 times solution, 6% chloropyrimidin 1000 times solution, 80% enemy bacteria 800 times solution, 12.5% ​​speed Poly 3000 to 4000 times solution, 12.5% ​​special azole wettability Powder 3000 ~ 5000 times liquid, 40% Fuxing emulsifiable oil 8000 ~ 10000 times liquid, 10% Shi high water dispersible granules 6000 ~ 7000 times liquid, 25% nicotazole emulsifiable concentrate 4000 times liquid. In the case of production control, if the same agent is used continuously for a long time, it will produce resistance and should be used interchangeably. For orchards with a large number of onsets, the whole tree can be sprayed with 10 to 20 times of urea water or 10 to 20 times of sulfur ammonia solution in the whole tree before the green buds are exposed to green to kill the germs on the buds.
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