Stem borer is one of the most common and damaging insect pests in maize in India. Many farmers first notice the problem when they see “dead heart” in young maize plants or when the crop looks uneven with weak, stunted plants. Stem borer larvae enter the plant and feed inside the whorl and stem, so the damage is hidden at the beginning. If the attack is not managed early, it can reduce plant population, lower cob size, and finally reduce grain yield. Understanding the symptoms and taking timely action is the best way to protect the maize crop.
Stem borer attack usually starts in the early stage, around 15 to 35 days after sowing, but it can continue later as well. The adult is a moth that lays eggs on the underside of leaves. After hatching, small larvae feed on leaf surface for a short time and then move into the whorl. You may see small holes in the leaves arranged in a line. This is called “shot hole” symptom. As larvae grow bigger, they bore into the stem. When the central shoot is damaged, the inside leaves dry up and the plant shows dead heart. In severe cases, the plant may stop growing, produce no cob, or produce a very small cob.
Farmers should monitor the crop regularly, especially during the early growth stage. Look for egg masses, shot holes, frass (insect waste) in the whorl, and dead heart symptoms. If you split the stem of an affected plant, you may find the caterpillar inside. Early detection is important because once larvae go deep inside the stem, spraying becomes less effective.
Field conditions and management can increase stem borer problem. Late sowing often faces higher pest pressure because the pest population builds up in the season. Fields near sugarcane, sorghum, or maize stubbles may have more infestation because the pest survives in residues. Heavy nitrogen application can make plants soft and more attractive to pests. Also, weeds on bunds and around the field can act as shelter for adult moths.
The first step in managing stem borer is prevention. After harvest, remove and destroy maize stubbles and crop residues, because larvae and pupae survive inside them. Deep ploughing exposes the pest stages to sunlight and birds. Crop rotation also helps—avoid growing maize continuously in the same field if possible. Timely sowing is another important practice. When maize is sown at the recommended time, the crop grows vigorously and escapes heavy early attack.
Balanced fertilization strengthens the plant and reduces damage. Avoid excess nitrogen in the early stage and apply fertilizer in split doses. Keep the field clean and remove grassy weeds that can host the pest. In small fields, removing and destroying dead heart plants can reduce pest spread, especially when infestation is in patches.
Biological and eco-friendly methods are also useful. Installing pheromone traps helps in monitoring adult moths and reducing mating. Bird perches can encourage insect-eating birds to visit the field. Some farmers apply bio-based products that target young larvae in the whorl. These work best when applied early and repeated if needed.
When infestation crosses a safe level, chemical control may be necessary. The best time for control is when the larvae are small and still present in the whorl. Applying recommended granular insecticides into the whorl or root zone is often effective because it reaches the area where larvae feed. Sprays can also work if directed properly into the whorl, but they should be done early. Always use only recommended insecticides, follow the correct dose, and ensure safety while handling. Rotate products to avoid resistance.
In short, stem borer in maize becomes serious when it is ignored in the early stage. Regular monitoring, timely sowing, residue management, balanced fertilizer, and early control in the whorl stage are the keys. With these steps, farmers can reduce dead heart damage, protect cob development, and get better maize yield and profit.
