Fall Armyworm (in maize) is a harmful insect of the Lepidoptera order whose scientific name is Spodoptera frugiperda. These insect infestations are most common in the Americas.
Recently, the Indian states of Karnataka and Tamil Nadu have seen infestations of this insect which is spreading to neighboring areas and Bangladesh as well. The insect is already spreading to maize-growing areas across the country, including northern and western parts of Bangladesh, with the potential for massive crop losses.
A major pest of maize worldwide is the fall armyworm or common cutworm. Only one pest becomes a major pest or a major pest when alternative hosts are present and control management is difficult. Each of these three characteristics is present in this insect. Although it is mainly an insect of the American continent, in 2016 Africa and in 2018, the attack of this insect occurred in various countries of South Asia, especially in India, and Sri Lanka. Let’s learn today about the management of a devastating fall armyworm.
Attack Level, Life Cycle, And Symptoms of Damage:
This insect attacks about 80 types of crops including corn, sorghum, almonds, tobacco, various fruits, and vegetables. However, the attack rate is highest in maize. The insect eats the leaves and fruits of the plant in its larval stage. In the early stages of the worm, the food requirement is low, but as the worm grows, the need increases by about 50 times, especially towards the end. That is why in the last stages (4-6 stages) i.e. if the worm is full or extensive, it becomes a monster and causes great damage to the crop. It can even destroy entire crops in one night.
The life cycle of this insect is completed in four stages: egg-worm-pupa-adult. The insect completes its life span of 30-35 days in summer and 70-75 days in winter. The female insect lays 100-200 eggs below the base of the stem and leaf junction. The hatchlings begin to feed on the leaves and make Small rows of holes in the leaves. Young plants like to eat the ear-like parts of leaves and the leaves wrapped around the ears of corn on older plants. After feeding on the leaves surrounding the corn cob, they enter the cob and feed on the soft kernels that form on the cob. In between, the fall armyworms mature and grow, eating the leaves, defoliating them, and reaching the heads of the corn plant, causing extensive damage. Young plants stop growing and no new leaves grow. After about 14 days, the full-grown caterpillar falls to the ground to reach the pupa stage. At this time they stay 1-3 inches deep. Cover themselves with fallen leaves if the soil is too hard. After about 8-9 days the full-grown moth emerges from the soil and starts the life cycle again.
Ways To Identify:
- On the surface of the body, there are longitudinal dark spots on both sides.
- The head has web-like spots in an inverted Y letter.
- There are 4 black spots on the 8th segment of the surface of the insect.
How To Control Fall Armyworm in Maize?
A) Biological Control:
- Fall armyworm insect pheromone traps should be used to detect the insect’s location in the early stages and control them. In this case, 5-6 traps should be set per 14400 sqft in the land of corn or other nutritious crops. As well as regular inspections should be done.
- In order to control this harmful monster insect, the first thing to do is to treat the seeds at the time of corn planting.
- From the two-three leaf stage of the plant, the eggs or newly hatched clusters of worms should be collected and crushed or buried in the ground by digging a one-foot hole.
- Besides, hand picking should be continued till the mocha of corn is reached. Regularly inspecting the crop field and identifying the pest according to the symptoms and taking action.
- The affected tree and its surrounding area (covering 90-100 feet area) should be sprayed with fast organic herbicide Spodoptera nuclear polyhedrosis virus (NPV) at the rate of 0.2 g per liter of water and wet the affected tree well. In this way, 2 to 3 times organic herbicide SNPV should be sprayed after 7 days.
- Beneficial insects Bracon Habitor should be released into affected areas if possible. They lay their eggs on fruit armyworms. As a result, those insects cannot damage the corn.
- If rice is grown instead of maize or other host crops in the next crop, there is a possibility of reducing the attack of this insect.
- In Africa, as a local technique, soil or ash from the roots of infected maize plants and pepper paste or powder are mixed with water to make mud and are opened with a vessel or mug or inserted into the gap between the leaves. The worms die within 3-4 days. However, more research is needed in this regard.
B) Chemical Control of Fall Armyworm:
However, chemical pesticides are not very effective in controlling this insect. However, if necessary, Genezoite 5 WDG or Genethrin 10 EC should be used as usual.