Peanut
Velvetbean Caterpillar
Anticarsia gemmatalis
Insect
In a Nutshell
- Feeding damage on foliage and whole leaves.
- Feeding damage on buds, small bean pods and stems.
Peanut
Symptoms
The caterpillars of the velvetbean moth attack the leaves of their hosts. First, the young larvae feed on the soft tissue. Older instars feed on the entire leaves including the veins. At later stages, the larvae feed on buds, small bean pods and stems. They are mostly active during nighttime. They occur in very large numbers and are capable of defoliating a field of bean or other legume crops completely within a week if they are not controlled.
Recommendations
Organic Control
Use natural enemies to combat the velvetbean moth, for example several species of wasp parasitoids like Euplectrus puttleri and Meteorus autographae. Other observed predators are ground beetles, tiger beetles, the red fire ant or the tachinid fly Winthemia rufopicta. Vertebrate predators such as birds, frogs and rodents also diminish velvetbean moth populations. Or employ pathogens to reduce the velvetbean caterpillar population, for example the bacteria Bacillus thuringiensis.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments if available. A preventative treatment with insecticide provides the most promising results in controlling the pest.
What caused it?
The adult moths of Anticarsia gemmatalis have a wingspan of 30 to 40 mm. The forewings vary from ash grey to light yellowish-brown or dark reddish-brown. The hind wings are light brown with a row of light coloured spots near the margin. A dark diagonal line extends across both sets of wings when they are fully extended. The eggs are slightly oval, ribbed and white until just before hatching, when they turn pink.They are laid singly on the underside of leaves. After three to seven days the eggs hatched and the larvae feed on the shell of the egg they emerged from. The larvae of the velvetbean moth are extremely variable in coloration and markings throughout the instars stages. Young instars are sometimes misidentified as soybean loopers (Pseudoplusia includens). In the prepupal stage the larvae shrink to a length of 25 mm and turn mahogany brown. The pupae turns from light green to brown and is approximately 20 mm long. It lies directly underneath the soil surface. The life cycle is completed in about four weeks during the summer. When the temperatures decrease the life cycle takes longer. The number of generations per year varies between regions.
Preventive Measures
- Plant resilient varieties.
- Choose early-maturing cultivars.
- Plant early in order to harvest early.
- Monitor your plants carefully and implement disease management measures when critical number is reached.
- Use pheromone traps.
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