Stem borers are pests that cause significant damage to maize crops, also known as corn, a staple food and important cash crop for millions of people worldwide. One of the most severe maize insect pests. Damage results in a dead heart, which renders the plant earless in extreme cases and may cause loss ranges from 20-80% in maize. Also, the uninfested fields yield 28% more harvest than infested fields. Let’s check out more information on Stem Borer management in Maize farming below.
Stem borers are the larvae of moths that lay their eggs on the stems of maize plants. When the hatching of eggs occurs, the larvae burrow into the stem and feed on the plant’s tissues, causing significant damage. This damage can lead to reduced yields and even complete crop failure. To control stem borer infestations, farmers use a combination of cultural, chemical, and biological control methods, including planting resistant varieties, crop rotation, and the use of natural predators such as birds and parasitic wasps.
Stem Borer management in Maize
The life cycle of Maize Stem Borer
- Eggs laid in batches on both host and non-host plants (10-80 per batch) Freshly hatched larva search for host plants Leaves enclosed in whorl – preferred by the larva
- The larva undergoes six instars of moulting five times. Pupation- Inside larval tunnel or outside plant (exit holes are visible)
- Most favorable temperature for development: are 30 C 5 generations per year in Chitwan conditions
Identification of Stem Borer in Maize field
- The egg is small, spherical, and has radial ridges. The larvae start dark brown and become paler as they mature, reaching a length of 35-40 mm.
- The pupa is dark brown and found in maize stalks.
- The adult is an owlet moth with a light brown to copper brown forewing and a greyish-white hind wing, with a wingspan of 25-35 mm.
Factors favoring population increase of Stem Borer in the Maize field
- Favorable environmental conditions: Stem borers thrive in warm and humid environments, so areas with high temperatures and rainfall are particularly susceptible.
- Lack of crop diversity: Monoculture crops, such as maize, provide an ideal habitat for stem borers as they can feed on the same plant continuously without interruption.
- Late planting: Late planting can allow increased stem borer populations to establish and damage the crop before it is harvested.
- Crop residue management: Improper disposal of crop residue can provide a habitat for stem borer eggs and larvae, leading to an increase in populations.
Damage symptoms of Stem Borer in Maize field
- Central shoot withers and leads to a “dead heart.”
- Larvae enter the stem through the midrib and feed on the internal tissues.
- Boreholes can be seen near the nodes on the stem.
- Young larva crawls and feeds on tender folded leaves, resulting in the characteristic “shot hole” symptom.
- Internally tunneling caterpillars may be seen in affected stem parts.