Stem Borer

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Stem Borer

Coniesta ignefusalis

Insect


In a Nutshell

  • Attacks growing tips and leaves, and carves into stems.
  • Larva of 20 mm with reddish-brown head and white body.
  • Eggs are laid in batches and have a yellow color.

Hosts

Millet

Symptoms

The larvae of the Stem Borer attack the leaves and leaf tips of millet. The larvae bore holes into the stem and carve it out, which leads ultimately to death. The fully grown larva is about 20 mm long and has a reddish-brown head and a white body which can also be black-spotted. The adult moth has a wingspan of about 8 to 15 mm with white wings. The eggs of the stem borer are laid in batches on the leaf and have a yellow color.

Trigger

In wet regions there are three generations of larvae per year, while in dry regions two cycles occur. The Stem Borer carves out the stem, so the flow of water and nutrients from the roots to the rest of the plant is impeded. The larvae of the Stem Borer survive in the the residue of the crop.

Biological Control

You can reduce the population of Stem Borers with the help of pheromone bait traps. The traps should be placed along fences (especially if they are made out of millet stems or other grasses) and granaries. Applied early in the season on infested plants, neem oil can be effective against Stem Borers. The ‘push-pull’ method can be very effective: Crops like Desmodium can be intercropped with millet. Desmodium acts as a repellent, so the moths are ‘pushed’ away from the millet. You can plant field trap crops like Napier or Sudan grass on the border of your plantation. These crops will attract the moths, so they are ‘pulled’ away from the millet.

Chemical Control

Insecticides are often difficult to use as well as expensive. Dimethoate can be used but rarely justifies the costs.

Preventive Measures

Use resistant varieties if locally available.,Plant crops early to avoid infestation.,Plant non-host crops, such as cowpeas, among the host plants.,Stimulate populations of natural enemies (parasitoid wasps) by planting flowering strips around the field.,If the stems are used in building structures, partially burn them.,Clean up and destroy all harvest residues.