What Does the Armyworm Look Like and What Pesticide to Use? A Detailed Guide to Control Techniques

The armyworm is an insect, also known as the millet cutworm and the branch-cutting worm. Common names include the five-colored worm and wheat silkworm. Its hosts include wheat, rice, millet, corn and other cereal grain crops, as well as cotton, beans, vegetables and more than 104 species of plants in over 16 families.So what does the armyworm look like? What pesticide works best? What control techniques are there?

What does the armyworm look like?

1. Egg: about 0.5mm long, hemispherical, initially white when laid and gradually turning yellow, glossy. The eggs are arranged in a single layer in rows and clusters.

Larva: the mature larva is 38mm long. The head is reddish-brown, the head capsule has a reticulated pattern, the frons is flattened, and there are thick brown longitudinal stripes on both sides, roughly forming a splayed shape, with brown reticulation on the outer side. Body color ranges from pale green to deep black, varying greatly (often changing with food and environment); during major outbreaks the back is often black, the underside pale and dirty-colored, the dorsal midline white, the area between the subdorsal line and the spiracular upper line slightly blue, and the area between the spiracular line and the spiracular lower line pink to grayish-white. The outer side of the prolegs has a broad dark brown longitudinal band, and the tip of the proleg bears a semicircular row of dark brown crochets.

2. Pupa: about 19mm long, reddish-brown, with a row of dentate punctures on the anterior margin of the dorsum of abdominal segments 5 to 7; the cremaster bears 4 spines, the central 2 thick and large, the lateral ones slender, short and slightly curved.

3. Adult: body length 15 to 17mm, wingspan 36 to 40mm. The head and thorax are grayish-brown, the abdomen dark brown. The forewings are grayish-yellow-brown, yellow or orange, highly variable; the inner transverse line often appears as only a few black dots, the orbicular and reniform stigmas are brownish-yellow with indistinct borders, the posterior end of the reniform stigma has a white dot with a black dot on each side; the outer transverse line is a row of black dots; the subterminal line runs obliquely inward from the apex to Mz; the terminal line is a row of black dots. The hindwings are dark brown, gradually paler toward the base.

What pesticide works best for the armyworm? What control techniques are there?

1. Control the larvae, reduce the damage, and lower the population base. Following the principle of “using contact insecticides as the main attack on young larvae and stomach poisons to supplement control of older larvae”, spray promptly at the early stage of the second-generation larval outbreak, and try to eliminate the larvae before the 3rd instar.

(1) Control when the threshold is reached. When the pest density in rice fields reaches 15 to 20 larvae per sq m, or in corn fields reaches 10 larvae per 100 plants or more, per mu you can use 50% phoxim emulsifiable concentrate, 80% dichlorvos emulsifiable concentrate, or 40% chlorpyrifos (Lorsban) emulsifiable concentrate at 75 to 100 grams mixed with 50 kg of water, or 20% diflubenzuron No. 3 suspension concentrate, or 25% cyanide middot; phoxim emulsifiable concentrate at 20 to 30 ml, or 4.5% beta-cypermethrin at 50 ml mixed with 30 kg of water for uniform spraying, or use 5% fenpropathrin (Meothrin) emulsifiable concentrate, 5% fenvalerate (Sumicidin) emulsifiable concentrate, 2.5% lambda-cyhalothrin (Kung Fu) emulsifiable concentrate, or 2.5% deltamethrin (Decis) emulsifiable concentrate at 1000 to 1500 times dilution, 40% omethoate at 1500 to 2000 times dilution, or 10% imidacloprid at 2000 to 2500 times dilution for spray control.

(2) Early control. At the young larval stage, you can use 5% flufenoxuron emulsifiable concentrate at 4000 times dilution, or diflubenzuron No. 1, diflubenzuron No. 2, or diflubenzuron No. 3 at 500-1000 times dilution for spray control, which is effective against armyworm larvae and does not harm natural enemies.

2. Operate scientifically and use pesticides safely. Spraying should be done before 9 a.m. on sunny days or after 5 p.m.; if rain occurs, respray promptly. Spraying should be uniform and thorough, covering the field edges and roadside weeds. When the larvae are older, appropriately increase the dosage. For fields with extremely high pest numbers, you can first shake the plants to knock the armyworms to the ground, then spray the ground, which can achieve good results. Spraying machinery can include self-propelled sprayers for tall crops, air-assisted sprayers, or smoke sprayers. When spraying, wear protective clothing and a mask.

3. Build blocking belts to prevent migration. When armyworm larvae migrate to cause damage, you can dig deep trenches along their migration paths and centrally dispose of the armyworms that fall into the trenches to stop them from migrating further; or spread a 15 cm wide pesticide belt as a blockade; or in wheat and corn fields, broadcast phoxim toxic soil to establish an isolation belt.

4. Control adults to reduce egg-laying. Taking advantage of the adult armyworm's egg-laying habits, phototaxis and chemotaxis, use grass bundles, sugar-vinegar liquid, sex pheromone traps, insecticidal lamps and other methods to trap and kill adults, so as to reduce the number of eggs laid by the second-generation adults, lower the field pest density, and reduce the outbreak base and control pressure of the third-generation armyworm.

(1) Grass bundle method. Generally, make grass bundles about 5 cm in diameter and insert 60 to 100 per mu, replacing the bundles every 5 days, and centrally burn the replaced withered grass bundles to destroy armyworm eggs.

(2) Sugar-vinegar method. Take 350 grams of brown sugar, 150 grams of liquor, 500 grams of vinegar, 250 grams of water, and add 15 grams of 90% crystalline trichlorfon to make a sugar-vinegar attractant liquid, and place it 1 m high in the field to trap and kill adult armyworms.

(3) Sex pheromone trapping method. Use a dry trap equipped with an armyworm sex pheromone lure, placing 1 per mu on a pole hung in the corn field to trap and kill egg-laying adults.

(4) Insecticidal lamp method. During the adult mating and egg-laying period, set up insecticidal lamps in the field with a spacing of 100 m, turning the lamps on from 8 p.m. to 5 a.m. to trap and kill adults.