The cotton ape is also known as a thrips, belonging to the order Thysanoptera and Thripidae. In recent years, the occurrence of hazards in Xinjiang has increased. Organic Rice
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First, the harmful symptoms of è“ŸMa Cheng, nymphs sucking mouthparts feeding. With the different parts of the cotton seedlings damaged by the thrips, the symptoms of the damage are not the same.
1. Silvery white spots appear on the backs of cotyledon victims, yellow-brown spots appear on the front, spots are contiguous when severe, and the leaves become thicker and the cotyledons dry off.
2. After the leaves of the true leaves were damaged, there were holes of different sizes and irregular edges. The older true leaf victims suffered silvery white spots, plaques, and black dots along the leaf veins and yellow-brown spots on the front. The leaves became thicker, brittle, and rougher. In severe cases, the leaves turned to the front and the cotyledons became dry and fall off.
3. At the time of growth, the victim's cotyledon growth point suffers damage, forming a "headless cotton" and eventually dies, resulting in a lack of seedlings and ridges. If the victim cotton seedling is large, a "long plant" with no main stem is formed.
Second, the law of the occurrence of cotton fleas horse nymphs and larvae mainly winter, overwintering place for the topsoil, earth seams, clods and litter. The southern border began in late October and was completely dormant in late November. The northern border was earlier. In the following year, southern Xinjiang began its activities in the middle of April in the end of March and early April. When the average daily temperature reaches 10°C, overwintering occurs successively, and adults can feed. In mid-to-late April, when the average temperature is above 12°C, adults lay eggs and breed, completing a period of 20-30 days in the spring and fall of the generation and 15-18 days in the summer. The 2nd instar larvae are more active, often accumulating damage on both sides of the veins and near the petiole. After the cotton seedlings are unearthed, the thrips begin to harm the cotton fields. When the cotton seedlings are in the cotyledon stage to 1 to 2 true leaves, the main damage to the growing point is the main period of “headless cottonâ€, which is harmful to the cotton fields. The first period. Although the density of thrips in the cotton field was not large at the time, it was often hidden in hidden areas, and sometimes fell into the soil with a drop in temperature, so it was not easy to find. Since then, with the rapid rise in temperature and the maturity of other hosts, there will be a sharp rise in the number of horses in the cotton field, reaching a peak period, which is mainly to harm the cotton leaves, and is the second flood period in the cotton field. Then the number of horses in the cotton field drastically decreased.
Third, development trends and causes
1. Development Trends As a whole, there is a clear tendency to increase, especially in southern Xinjiang. According to this year's survey, the damage level of the thrips in the cotton fields of the Tarim Reclamation Area (such as 32 groups) of the Agricultural Division 2 has increased. The group 3 farms generally believe that the occurrence or harm of thrips is more serious than that of previous calendar years, and the number of "headless cotton" and "long cotton" strains in some untreated fields is as high as 10% or more. Severe bar-field "headless cotton" and "long cotton" have reached more than 20% in Shache County. In addition to the changes in the number and degree of harm, the occurrence period of the hummer has also been prolonged. It not only enters the ground early but also lasts a long time. On the other hand, there are large differences between regions. South Xinjiang is more important than northern Xinjiang, and the Xiaohaizi area is slightly heavier than the Meghati area, while the 46th group is more important than other units.
2. The first occurrence is geographical and climatic factors. The warm weather, low rainfall, and arid climate of Hummerxi are suitable for temperatures ranging from 23 to 26°C and humidity of 40% to 70%. High temperature and high humidity adversely affect the breeding of thrips. Therefore, Xinjiang is the heaviest region in the nation's Hummer, and southern Xinjiang is more important than northern Xinjiang. This also applies when analyzing the microclimate area. The second is the influence of cultivation factors, such as the previous crop (continuous cropping), neighboring cropping, intercropping, and sowing date. It should be noted that long-term continuous cropping of mulch cotton and wintering with a large number of cotton fields will aggravate the occurrence of thrips in cotton fields. The third is the treatment of seed and pesticide in different regions. In general, the occurrence and harm of thrips will be significantly reduced in the case of pesticide seed dressing and seedling application. The fourth factor is the natural enemies. Cross beetles, horses, flowers, hawksbills, grasshoppers, ladybugs, spiders, etc., can all eat predators. Enormous natural enemies, or attention to the protection of natural enemies, are conducive to reducing the occurrence and harm of thrips. .
Fourth, prevention
1. Seed Treatment The pesticides commonly used in our area such as formazan and acephate are all effective for the thrips. Need to pay attention to two issues, first, pay attention to the appropriate dosage, such as 40% acephate in general should not be less than 1% of the seed amount, and in the severe areas of thrips may consider increasing the dose to 1.5%; Correctly solving the problem of seed coating agent use and pest prevention, the current technology should be based on Jinhua seed coating agents and insecticides.
2. Seedlings can be sprayed to control cotton fields that have not been treated with seed or severely affected by thrips. The commonly used agents are dimethoate and acephate. The spraying time must be performed immediately after the seedlings. The latest should not be later than the arrival of a large number of natural enemies before entering the land. In southern Xinjiang around May 1st.
3. Others adopt autumn plowing and winter irrigation, and do not co-operate with crops such as scallions, melons and other crops, or continue cropping.
Author: Xinjiang Kangzheng Agricultural Science and Technology Development Co., Ltd. Kashgar forty-eighth regiment