African bollworm and other pod borers
Several caterpillars are important pests as pod borers in common beans and French beans. The most common are the African bollworm (Helicoverpa armigera) and the legume pod borer (Maruca testulalis). They feed on leaves, flowers, pods and seeds. The African bollworm caterpillars are 3 to 4 cm long. They make clean circular holes in the pods. One caterpillar may damage several pods. Caterpillars of the legume pod borer attack pods at the point of contact with other pods, leaves or the stem. They frequently web together flowers, pods and leaves with excrements.
Pod borers usually do not cause significant yield reduction in beans. However, they are quarantine pests, and are particularly important in French beans grown for export. If only 1 caterpillar is found in a consignment sent to Europe, the whole consignment may be rejected. If pod borers are found in a field, the beans harvested should be sorted very thoroughly to remove the bollworms manually.
- Monitor the crop regularly
- Handpick and destroy infested pods and pod borers. This helps when their numbers are low and in small fields.
- Spray crop with biological pesticides (e.g. Bt products or neem). For more information on Neem click here. For information on Bt click here.
- If pod borers are found in a French beans field, sort harvested pods very thoroughly and remove pod borers manually.
Helicoverpa armigera (Synonym: Heliothis armigera)