The harm of Oncomelania hupensis and its control measures

The snail can bite off the main tillers and effective tillers of rice, resulting in a reduction of effective panicles and a yield reduction of more than 20%. In addition to eating rice and other aquatic plants, it also spreads diseases such as Angiostrongylus cantonensis. People can be infected after eating raw or incompletely heated snails, which can cause eosinophilic meningitis and meningoencephalitis, causing headache, dizziness, fever, neck stiffness, facial nerve paralysis and other symptoms. in severe cases, there will be paralysis, lethargy, coma and even death.

The snail was introduced into Taiwan in the 1970s and introduced to Guangdong by Brazilian Chinese in 1981. Since 1984, Oncomelania hupensis has been widely cultivated in Guangdong. Due to overfarming and bad taste, it was released into the wild. Oncomelania hupensis has a strong ability to adapt to the environment and propagates quickly, so it spreads rapidly in rivers, lakes and fields. Its large food intake and a wide variety of food can destroy the growth of food crops, vegetables and aquatic crops. It has become a pest in Guangdong, Guangxi, Fujian, Yunnan, Zhejiang, Shanghai, Jiangsu and other places. In the vast area south of the Yangtze River, the snail can survive the winter naturally, occurring for two generations a year. In Luzhai County, Guangxi and other places, the occurrence density of Oncomelania hupensis in rice fields is as high as 16.95 per square meter; the rate of damaged rice plants is generally 7% to 15%, with a maximum of 64%. Fushou snail has miscellaneous feeding habits and harms the lotus root. Young snails can gnaw the lotus leaves floating on the water surface from the bottom of the leaves, causing the lotus leaves to be perforated or engraved. In serious cases, the leaves are riddled with holes and difficult to pull out of the water. The snail also harms all kinds of aquatic plants such as daffodils and orchids and has become a major disaster in the waters of southern China. In addition, Oncomelania hupensis is also an intermediate host of zoonotic parasitic diseases, which can easily bring health problems to the surrounding residents. It is estimated that the affected waters (ponds, lakes, paddy fields, etc.) of provinces and cities in southern China are not less than 100000 hectares. The control of Oncomelania hupensis is mainly chemical control, supplemented by artificial control. Duck snail feeding is one of the biological control methods. The ecological habits of Oncomelania hupensis are not well understood and the prevention and control is not effective. In particular, the selected chemical molluscicide has great toxicity to the water body, seriously pollutes the water quality, and has the advantages of large dosage, high cost and poor effect.

Agricultural control measures of Oncomelania hupensis

1. Eliminate the source of overwintering snails: Fushu snails are mainly concentrated in streams and rivers and low-lying water in ditches, so it is necessary to clean up the ditches at the edge of rice fields before spring ploughing, remove silt and weeds, and destroy the overwintering places of Fushun snails. reduce the survival rate of overwintering snails and the amount of residual snails after winter. At the same time, drugs are used to prevent and cure ditches and low-lying stagnant water.

2. Blocking transmission: in the downstream area of the re-occurrence area, a barrier net is installed at the entrance of the irrigation canal or at the inlet of the rice field to prevent the snail from entering the field with the water.

3. Artificial hunting: during the peak spawning period in spring, combined with field management, the egg blocks in the fields and ditches are removed, taken away from the rice fields to feed ducks or crushed. When drying the field, the adult snails are mainly concentrated in the inlet and drainage and the seedling ditches, and the snails are picked up manually in the morning and afternoon. Artificial removal of egg blocks and picking up snails when combined with farming. When drying the field, the adult snail is mainly concentrated in the inlet and drainage and the seedling field ditch to collect the snail manually, which can also control the damage.

4. Artificial trapping: after the paddy field was flooded, 30cm high bamboo slices (wood strips and rape straw) were inserted into the paddy fields to induce the snail to lay eggs on the bamboo slices (wood strips and straw), and the egg blocks were removed and destroyed every 2 to 3 days. The quantity of 3080 bamboo slices (wood strips and straw) per mu should be planted near the edge of the field to facilitate the removal of egg blocks.

Biological control measures of Oncomelania hupensis

Biological control is mainly adopted to raise ducks and feed on snails. The duck release time is from 7 to 10 days after rice transplanting to the late booting stage of rice, and the flocks of ducks (15 to 30 ducks per mu) are released every morning and at 5: 00 or 6: 00 in the afternoon to peck at young snails in rice fields and canals to reduce the number of snails and reduce damage.

Chemical control measures of Oncomelania hupensis

The main results are as follows: 1. Control index: 2 heads per square meter at seedling stage, 1 egg block per square meter at field edge, 3 heads per square meter at tillering stage and 1 egg block per square meter.

2. Control agents: 10% snail snail granule, 6% Mida molluscicidal granule, 50% molluscicidal ethanolamine salt wettable powder, 70% molluscicidal wettable powder, 45% tin triphenylacetate wettable powder and so on.

3. Application period: two times of application: 2 leaves and 1 heart stage of rice in ① seedling field. ② was applied when transplanting. If the snail damage is serious, the pesticide should be applied once every 10 days.

4. Application method: the dosage of ① 10% snail cochlea granule is about 400-500g per mu, evenly spread in the field or mixed with fine soil 5~10kg. The dosage of ② 6% Mida molluscicidal granule is about 400g / mu, which is evenly applied in the field or mixed with fine soil 5~10kg. ③ 70% spirosemide ethanolamine salt wettable powder is sprayed with 60 grams of water and 20 kilograms of water per mu.

5. Precautions: when ① was applied, the water layer in the field was 1cm to 3cm, and the water was preserved for 7 days. If it rains heavily within 24 hours after ② application, it needs to be replenished once. ③ molluscicide is toxic to fish. 7 days after application, the field water should not be discharged into the fish pond, and the stocking of ducks is prohibited.