Analysis on the Occurrence Trend of Main Diseases and Pests of Crops in Changsha City in 2007

Analysis on the Occurrence Trend of Main Diseases and Pests of Crops in Changsha City in 2007

Changsha Plant Protection Station

On March 28th, I stationed the county plant protection station chiefs and forecast experts of crop pests and diseases to conduct topical discussion and analysis on the occurrence trends of major diseases and pests of crops in 2007 in the city. It is expected that the main crop diseases and insect pests in our city will be moderately heavy (level 4). The development of ecological potential. Rice rice planthoppers and sheath blight (Grade 5) occurred, rice leaf roller planted moderately (Grade 4), Brassica napus, and cabbage, Spodoptera litura, Plutella xylostella, Brassica juncea, and soybean meal on vegetables. Diseases of rice bran, melon, downy mildew, soft rot, and bacterial wilt with moderate to medium weight (grades 3-4), rice blast, thin strip disease, and rice smut mild to moderately mild (level 1-2) ) The quarantine pests rice water weevil and the newly emerging rice downy mildew occurred in some local areas, and the extent, area, and degree of occurrence were all more severe than in the previous year.

I. Rice pests and diseases

Trend analysis:

1. Rice planthoppers: Occurrence (level 5). The degree and area of ​​occurrence are similar to last year. It is estimated that an area of ​​5.5 million mu will occur. The first and second generations were less severe (level 1-2), the third generation occurred moderately (level 4), and the fourth and fifth generations occurred (level 5).

2. Insect leaffolders in rice: Occurrence of moderate stress (Grade 4), of which Liuyang city occurred in large numbers, and the other three counties were moderately overweight. It is estimated that an area of ​​4.75 million mu will occur. The first and second generations were less severe (levels 1-2), and the third and fourth generations were moderately heavy to occur (level 4-5).

3. Erhuacuan: Moderately heavy (Grade 4), with moderate occurrences in Changsha and Wangcheng County, moderate occurrence in Liuyang City and Ningxiang County. An area of ​​2.5 million mu is expected to occur. The generation is the main damage generation of the whole year, with the most serious occurrences, with moderate occurrences (Grade 4), and second, third, and fourth generations of moderate to moderate occurrences (Level 2-3).

4. Rhizoctonia: Occurrence occurs throughout the year (Level 5). It is estimated that an area of ​​4.5 million mu will occur.

5. Rice Weevil Weevil: The quarantine insect pest rice water weevil has rapidly expanded in our city in 2006. It occurred in 119 villages in 25 townships in Changsha, Ningxiang, Wangcheng and Tianxin districts of our city. 25.5 million mu. The public area has an area of ​​106,000 mu. This year, rice water weevil continues to show a rising hazard in our city, and it is serious in some places. An area of ​​500,000 mu is expected to occur, and the area will further expand.

6. Rice downy mildew: In recent years, rice secondary downy mildew disease in our city has occurred in Liuyang and Changsha counties in our city in 2006. Ningxiang County also occurs. In 2006, the city had an area of ​​294,500 mu. The aggravating situation occurred in 2007, and the local area where the disease has already occurred will be severe. It is estimated that the area will reach 400,000 mu, and the area will further expand.

7, other pests: rice blast, thin strip disease, false smut rice and rice weevil, armyworm, rice thrips and other large areas will occur from light to moderately light (level 1-2). However, in rice blast disease and rice smut disease in some areas, areas with large areas of cultivated cultivars of susceptible cultivars may have outbreaks if disaster-prone climate is suitable for disease occurrence.

Forecast basis:

1. Impact of cultivation cultivation system on the occurrence of diseases and insect pests: The city plans to plant 5.21 million mu of rice this year, including 2,189,100 mu of early rice, 612,000 mu of rice in one season, and 2,309,900 mu in double nights. One-season rice is mainly planted with flowers, which provides bridges that are damaged in the fields for the main pests and is very beneficial to the occurrence of diseases and pests. The cultivation of rice in Liuyang City is dominated by one-season rice. The planned area of ​​rice is 1.01 million mu, including 250,000 mu of early rice, 480,000 mu of one-season rice and 28.2 million mu of double-season rice. The area of ​​rice in one season is large, especially for the third generation rice leaf roller. This is favorable, which is also the reason for the occurrence of rice leaf curling in Liuyang County. This year, the city has the following characteristics in the farming system: First, the proportion of high-quality rice is large. High-quality rice is generally more resistant to disease, and it is very beneficial to diseases such as rice blast. This year, the high quality rice area in the city is expected to reach 3.8 million mu, accounting for 73% of the rice planting area; the second is the large-scale promotion of light cultivation techniques. This year, the city's area of ​​dry seedlings accounted for 90% of the early rice. Due to the early emergence of rice dumplings, rapid rice delivery, and a few seedlings, it provided a rich source of food for pests and caused shading in fields and high humidity, especially for rice pests and diseases. A generation of S. japonicum has an advantage; the third is a large area harvested by machinery. In 2006, the city's mechanical cutting area accounted for 59% of the rice area. According to the survey on the bases of occurrence of diseases and insect pests at various stations in the city after the winter, mechanically harvested 8525 pieces of insects per acre, which is 1.35 times more than the artificial reaping of 3,623 pieces of acre per acre. Mechanical harvesting fields are very beneficial to the occurrence of stem borer; the fourth is The area of ​​the insect source field is still relatively large. According to the incomplete statistics of the city, the effective insect field area is 820000 mu, which is basically similar to the 816,000 mu of the previous year.

2. The base number of pests in winter is relatively large, which is beneficial to pests and diseases: According to the post-winter survey in mid-March of each county station in the city, the city's weighted average of 4,766 larvae of larval warts per acre has decreased by 38% compared to the previous year. In those years where the base number is small, but compared with historical data, it is still a relatively high residue base and still has severe conditions. After the winter, the mortality rate of S. indica was 1.3%, which was 2.33% lower than the 3.63% in the same period of last year. The mortality rate of T. japonicum was not high, but the residue base was less than that of the previous year. The analysis was mainly due to the effective prevention and control of the fourth generation of T. sinensis in the past year, and the large base area before the winter was low. The city's average residual sclerotinia per acre was 124.6 thousand in the winter, a decrease of 23% compared with 162,300 sclerotia per acre in the same period of last year. Although the nucleus biomass of the sheath blight has been decreasing in recent years, There is still a major base of occurrence. In 2006, the area of ​​rice blast, sheath blight and thin strip disease in the whole city was relatively large, providing sufficient bacterial sources for disease occurrence. The early occurrence of rice water weevil is a long-term hazard, and the base number is large. It is an important signal that rice water weevil will be aggravated. The symptoms of damage caused by weeds have been found on March 20 in Changsha County station. Last year, it was 12 months. It was discovered on a daily survey that weeds were damaged. Ningxiang County surveyed three sites on March 20th and investigated a total of 1.08 square meters of weeds and topsoil. On average, there were 3.7 head rice weevil adults per square meter, including 5.6 heads of field ridges and 1.8 heads of slopes.

3, climatic conditions suitable for the occurrence of pests and diseases: to winter and this spring is still a cold winter weather, a variety of diseases and insect pests overwintering is beneficial, the mortality rate after the cold of the second season after the winter, the city's average after-stem mortality rate of 1.3%, The same period last year decreased by 2.33 percentage points. According to the weather forecast of the city’s meteorological observatory in 2007, the city’s total precipitation from April to September is more than 10%, including slightly more in April and May, slightly less in June, normal in 6-8, and mostly 1-3 in July and September. to make. Precipitation is relatively concentrated in the middle of April and the first half of May. The rainy season ends normally (at the end of July) or is not obvious. Due to the relatively high precipitation, the precipitation is relatively concentrated in May and June, which is beneficial to the migration and landing of migratory pests, which is beneficial to the occurrence of rice planthoppers and rice leaf roller, and to rice blast and rice smut disease. In case of a rainy weather during the growing period, there may be an outbreak.

4. Changes in the supply of agricultural resources, coupled with low levels of farmers' prevention and control, will also lead to aggravation of pests and diseases. In 2007, the production and use of five kinds of highly toxic pesticides were completely banned. The replacement of pesticides requires that the time taken to control rice leaf roller and rice stem borer should be properly advanced. If farmers do not master well, the control effect will be poor. There are still many markets for the imidacloprid compound with very poor control of cornfieldworms. According to the Liuyang City Station survey, it accounts for 40%. In addition, the phenomenon of running, running, dripping, and leaking of most sprayers is serious, and the level of prevention and control by farmers is not conducive to pests and diseases.

Second, vegetable pests:

In 2007, the overall incidence of vegetable pests in our city was moderately serious (Grade 4). The occurrence of both diseases and insect pests was heavy. The disease in the early stages was more important than insect pests, and the pests in the later stages were more important than the diseases. Among them, Pieris rapae, Spodoptera litura, Plutella xylostella, Brassica oleracea, cardamom, melon bran, cucumber downy mildew, bacterial leaf spot, Chinese cabbage soft rot, Solanaceae bacterial wilt, lettuce downy mildew, Sphaerotheca and other medium-heavy hair loss and (grade 4), beet armyworm, Liriomyza sativae, earth tiger, yellow striped hop, virus disease, blight, anthrax, early and late blight, powdery mildew and other pests Moderately mild to moderate occurrence (level 2-3). The main basis for forecasting is as follows:

1, the current occurrence of a large number of pests.

On March 11th, Changsha County Station investigated that cabbage caterpillars were harmful to Chinese cabbage. The average number of insects was 100%, which was the same as last year. The average damaged leaf rate was 24.3%, which was 2.6 percentage points higher than that of the same period of last year. There was an average of 0.1 per leaf. The average disease rate of Chinese cabbage soft rot was 70%, and the diseased plant rate was 2.3% lower than the same period of last year. The downy mildew strain rate of lettuce was 100%, and the average diseased leaf rate was 11.6%, 2.4 more than the same period of last year. percentage point. On March 23, the Liuyang City Station investigated the rate of 2.0% for the sclerotinia sclerotiorum disease strain, 52.8% for the downy mildew disease strain of lettuce, and the diseased leaf rate was 7.4%. The cabbage worm was harmed on leafy vegetables, and the strain rate was 18.1%. There were 1.6 strains of insects and one hundred strains of eggs were 6.7 grains. On March 26th, investigations of yellow leaf strips caused serious damage to leafy vegetables, the strain rate was 13.5%, and one hundred strains had 15.9 insects. The Ningxiang County station system is estimated to be late this year. It started on March 12th, 10 days later than the previous year, and peaked on March 22, 12 days later. The peak number of moths was 10, the previous year. In 17 animals, total moths were also less than in the previous year. There were 30 moths hunted on March 1-27, compared with 113 moths retrieved during the same period last year. This year, the occurrence of the midgets was estimated to be moderate.

2. There are many varieties of vegetables, high multiple cropping index, strong resistance to pests and diseases, and low levels of control are very beneficial to vegetable diseases and pests.

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