Occurrence and spread of grassland moth Field hazards and identification and emergency prevention and control technologies
The grassland night moth is a major agricultural pest of the global early warning of the Food and Agriculture Organization of the United Nations, belonging to the genus of the gray-winged night moth in the family Lepidoptera noctuidae, and the beet noctus moth and the twill nocturnal moth are harmful insects of the same genus, with omnivorous, migratory and explosive characteristics, and its harm far exceeds that of the latter two pests. The grassland moth is harmful to the larvae feeding on plants, with a wide range of hosts, including 186 plants in 42 genera including corn and rice cereal crops, which generally cause crop yields to decrease by 20% to 30%, and cause harvest failures in severe cases. The large-scale invasion and spread of the grassland moth is bound to threaten agricultural production and food security, and it is imperative to do a good job in the prevention and control of the grassland moth.
1 Occurrence and spread of the grassland moth
The grassland moth has a wide host and differentiates into two biological types, namely the maize type that mainly eats corn sorghum and the rice type that staples rice forage grass. At present, the grassland moth that has migrated into China is mainly maize-type, but with the advent of the rice production season, rice-type populations may join. As of May 22, the province has Liangshan, Luzhou, Yibin, Panzhihua, Suining, Neijiang, Nanchong, Chengdu, Ziyang, Deyang, Dazhou and Guang'an and 12 cities and prefectures and 40 districts and counties to find the distribution and harm of grassland moth, preliminary investigation of corn field plant damage rate of more than 30%, a large number of leaf holes, heart leaf rot is serious, directly affecting plant growth and later yield.
The suitable average temperature range of grassland moth is 11 ~ 32 °C, which can adapt to harsh conditions such as high rainfall and drought, and it is predicted that the grassland moth will form an annual breeding area and a summer occurrence area in China, and there are wintering conditions in most areas such as Panxi and southern Sichuan in the province, which may become the annual breeding area of the grassland moth. The province's corn has spring corn, summer corn and autumn corn planting all year round, the province's statistical area of 1.8 million hm 2, southern Sichuan and sorghum 20,000 hm 2, suitable temperature and rich feeding materials for the grassland night moth to provide rich conditions, the future southerly air flow and irregular rainfall, will be very conducive to the grassland night moth continue to move from Myanmar, Yunnan, Guizhou and other places into Sichuan Province or from the low latitude of Sichuan has occurred in the area to the high latitude suitable area. It is predicted that in addition to the ganziaba and some plateau areas of Liangshan Prefecture, the grassland moth can be harmful in the Sichuan Basin and the Panxi region, and the area of insects can account for more than 40% of the total area of the province.
2 Field hazards and identification of the grassland moth
The corn-type grassland moth feeds on all aboveground parts except the roots of the plant. The meadow moth is a typical fully metamorphosed insect, and the feeding harm stage is the larval stage, and the 6-year-old larvae are the most harmful.
The grassland moth is harmful
Young larvae are infested with leaves, leaving translucent film-like "window holes" (window holes are similar to the hazards caused by beet nocturnal moth larvae), and larvae over 3 years old bite into the leaves to form holes of varying sizes (significantly different from the row holes caused by corn borers), and a large amount of granular feces can be seen in the heart leaf or in the male ear buds, and the larvae hide behind them, and the larvae also bite the male ears and fruit ears of corn. Larval identification has two distinctive features, one is a black (or orange) head with a pronounced yellow-white inverted "Y" pattern, and the other is a square arrangement of 4 dark spots on the front of the abdomen. The larvae are variable in color and cannot be used as a basis for identification. The larvae are suspended dead and curl up into a "C" shape after being disturbed. Male adults and twill nocturnal moth male adults are most similar in characteristics, body length of about 15mm, significantly smaller than the latter, the biggest difference is that the twill nocturnal moth forewing in the middle of the ring and kidney spots have 3 obvious white diagonal lines, but the grassland nocturnal moth does not.
3 Emergency prevention and control technology
3． 1 In the province-wide monitoring, early warning and technical publicity of the grassland night moth has invaded Sichuan, the competent agricultural and rural departments at all levels, management personnel and agricultural production entities collected the situation, publicized the spread of the insect through various media, warned of the risk of migration, and guided the installation of trap monitoring devices; Carry out on-site training meetings step by step, so that the production subject or monitoring personnel can have a preliminary identification of the field grassland night moth through the appearance characteristics, and send samples in time if there is any doubt, and carry out DNA identification.
3． 2 Scientific and rational use of pesticides
Grassland night moth in the Americas on organophosphorus, pyrethroids, carbamate pesticides has developed a high resistance, the current recommended control drugs mainly include polybactericide, Bt, methyl vitamin salt, chlorantran benzamide, acetamidine, cypermethrin and so on. The best time to apply the drug is in the early morning and evening, mainly spraying corn heart leaves and ears, if the larvae are in a young age (1 to 2 years old), the drug effect is best. In the corn field, the grassland moth is mostly mixed with corn borer, beet moth, armyworm, etc., and attention is paid to reasonable drug selection and application. If you want to apply the drug multiple times, remember to rotate the drug.
3． 3 Strengthen field management and improve crop stress resistance
Rational fertilizer and water management in the field promotes the healthy growth of crops, improves the insect resistance and insect tolerance of crops themselves, and reduces the loss of damage.
3． 4 Efficient use of chee-trap techniques
Adult grass moths are diurnal and nocturnal, with phototropism, it is recommended to install insecticidal lamps in the field to trap adult insects, and install 1 insecticidal lamp every 2 to 3hm 2. At the same time, the installation of pheromone traps, 1 set/667m2, monitoring and control dual-use, has a significant effect on reducing the number of adult insect populations in the field. Traps have bottle type, triangular sticky plate, boat-type sticky plate, etc., correct installation of the lure core, the sticky board is slightly more viscous to reduce adult escape.
3． 5 Artificial capture of larvae using suspended animation
After being disturbed, the grass moth larvae quickly curl up into a "C" shape, with obvious suspended death. Using this feature of larvae, larvae can be directly captured and killed in combination with field farming operations.
3． 6 Protect and exploit predators
Planting non-grass crops, increasing the diversity of field crops, enriching the shelter of natural enemies, combined with the scientific application of chemical pesticides, timely discovery, protection and cultivation of natural enemies of grassland nocturnal moths, and then optimize agricultural ecology, and have a good control effect on grassland nocturnal moths.