Pod-borers (African bollworm, Legume pod-borer, lima pod borer)
Pod borers such as the African bollworm (Helicoverpa armiguera), the legume pod borer (Maruca vitrata), and the lima bean pod borer (Etiella zinckenella) can cause serious economic damage. Young caterpillars of the African bollworm feed on leaves by scraping tissue for short time, and then bore into the pods and feed on the seeds with their heads thrust inside and most part of the body outside. The entry hole is large and circular. They also cause significant damage to flower buds and flowers.
Caterpillars of the legume pod borer (Maruca vitrata) are dull to yellow-white and often reach a length of 18 mm. Each segment has dark spots that form a distinct series along the length of the body. The head is dark brown to black. Caterpillars web together leaves, buds and pods and feed inside the web. Flowers attacked may be discoloured and have damaged or missing reproductive parts. Damage by this caterpillar also results in flower bud shedding and reduced pod production. Damaged pods have small, darkened entry holes on the surface.
Young caterpillars of the lima bean pod borer are green, later turning red. They feed inside the pod reaching a length of 14 mm. They are generally found in maturing and dried pods. Faeces in the form of granules are found inside the damaging pods. Once the caterpillars have entered the pods they are difficult to control and by then they have already caused damage.
- Monitor the crops frequently as there is only a brief period from hatching to entering buds or pods.
- Hand pick and destroy eggs and caterpillars. This helps when their numbers are low and in small fields.
- Biopesticides such as Bt or neem products usually give good control of pod borers, provided they are applied to the young caterpillars before they enter into the pods.
For more information on Neem click here.
For information on Bt click here