Nghe An: 1,400 hectares of winter corn have leaves damaged by fall armyworms

Tan Ky district is one of the localities with the largest winter corn acreage currently being damaged by fall armyworms in the province.

Fall armyworms are damaging hundreds of hectares of winter corn in Tan Ky district. Photo: Xuan Hoang

Mrs. Nguyen Thi Binh’s family in Xuan Lam hamlet, Nghia Hoan commune has more than 1 sao of corn at the 10-leaf stage. However, the entire corn crop has been damaged by fall armyworms to the point of losing all its leaves. Although Mrs. Binh’s family has sprayed pesticides twice, it has not been effective; the corn shoots still have many live worms. The surrounding corn crops also have similar symptoms.

By early October, Tan Ky had nearly 589 hectares of winter corn attacked by fall armyworms in the communes of Phu Son, Huong Son, Nghia Thai, Nghia Hoan, Tan An, Ky Tan, Tan Huong...

Mr. Nguyen Van Trinh - Head of the Plant Cultivation and Plant Protection Station of Tan Ky district

In Nam Dan district, fall armyworm is causing damage to a large area of ​​winter corn.

Mr. Nguyen Dinh The - Deputy Head of the District's Department of Agriculture and Rural Development said: By early October, Nam Dan had planted more than 1,500 hectares of winter corn at the 6-7 leaf stage. However, fall armyworms have damaged over 500 hectares, of which about 100 hectares are severely infected.

Localities with large corn areas damaged by fall armyworms include Nam Thuong, Nam Tan, Hung Tien... Currently, Nam Dan farmers are preventing this type of worm by spraying pesticides mainly according to the recommendations of professional agencies.

According to the Department of Crop Production and Plant Protection, by October 6, Nghe An farmers had planted nearly 10,800 hectares of winter corn. However, up to this point, fall armyworms have attacked and damaged an area of ​​over 1,400 hectares, of which about 200 hectares are heavily infected, with a density of 7-10 insects per year.², locally 20 - 25 individuals/m². Localities with high incidence of fall armyworms include Nam Dan, Tan Ky, and Dien Chau. It is expected that fall armyworms will cause damage to more areas in the coming time.

Corn plants damaged by fall armyworms. Photo: Xuan Hoang

It is forecasted that in the coming time, fall armyworm will continue to cause damage on a large scale, in areas with high worm density, greatly affecting the growth, development and yield of corn.

Mr. Nguyen Tien Duc - Head of the Provincial Department of Crop Production and Plant Protection said that the reason why fall armyworms spread so quickly over a large area is due to the biological characteristics of this worm: it eats well, lays many eggs, and moves far. In particular, it is competitive, so on a corn plant there is only one worm, forcing them to move to another corn plant to live, while this worm only causes damage to corn plants, not other plants. At the same time, this is a new pest, so the specialized agency does not have in-depth experience in prevention. Besides, farmers are not familiar with the spraying method recommended by the specialized agency, so the effectiveness is not high.

Corn areas with high density of larvae (2 - 3 larvae/m²and above), farmers spray pesticides with active ingredients: Indoxacarb, Lufenuron, Spinetoram, BT,... spray according to the recommended dose, spray on corn shoots, the most effective spraying time is when most worms are at the age of 1-3.

At the same time, people should plant genetically modified corn to limit damage from fall armyworms. Recently, according to Decision No. 3666/QD-UBND of the Provincial People's Committee dated September 18, 2019, Nghe An supports 800,000 VND/ha for purchasing genetically modified corn seeds to plant in concentrated corn areas of 5 hectares or more.

Characteristics of fall armyworm:Larvae have 6 instars, instar 1 - 2 the body is light green - light yellow is common. When larvae develop instar 3 - 6 they are grayish brown - dark brown with vertical stripes on the body. Instar 1 larvae are about 0.5 mm long, instar 3 larvae are 6 - 9 mm long; instar 6 larvae are 30 - 40 mm long.

On the forehead of the adult larvae, an inverted yellow Y shape is clearly visible, the dorsal surface is black with long, stiff hairs. On the dorsal surface, the last abdominal segment has 4 black spots arranged in a square.

Symptoms of corn plants damaged by fall armyworm:1st and 2nd instar larvae feed on the epidermis on the underside of young leaves, causing characteristic white square or rectangular marks. Older larvae feed on the leaves and leaf sheaths, creating large holes.

Prevention:Regularly check the fields, especially at the 3-6 leaf stage to detect egg nests and remove and destroy them. Use wood ash or diluted soapy water poured on the corn cobs to kill larvae.

Use active ingredients of pesticides allowed for use according to the instructions of the agricultural extension service to spray when the majority of worms are 1-3 instars (corn stage 3-6 leaves). Use pesticides according to the "4 rights" principle.

Can use light traps and bait to kill adult worms.