The African bollworm, scientifically known as Helicoverpa armigera, is a significant pest from the Noctuidae family. It poses a threat to the vegetative growth, flowering, and fruiting stages of host plants. With its aggressive feeding behavior, this insect pest can cause substantial damage to a wide variety of host plants, making it a highly impactful pest.
Occasionally, the African bollworm is also known by the name American Bollworm.
The African Bollworm displays polyphagous behavior, which means it attacks and causes damage to a broad spectrum of plants. Some of the plants it targets include:
- Legumes e.g. beans, cowpeas
- Cereals e.g. maize, sorghum
- Vegetables e.g. peppers, tomato
The eggs are deposited on different parts of plants and undergo hatching within a span of 2-5 days, transforming into larvae. These larvae, commonly known as caterpillars, feed on the plants for approximately 16-30 days during their larval stage. Once they reach full maturity, the caterpillars detach from the plants and dig into the soil to enter the pupal stage. Pupation occurs underground and lasts for about 15-20 days. The entire life cycle, which can vary in duration (25-60 days), depends on environmental factors such as temperature.
- The adult form of this species measures approximately 18-25mm in length, with a wingspan spanning 35-40mm. It displays a yellowish-brown coloration, featuring a distinct dark speck, grey irregular lines, and a black mark on the forewings. The hind wings are whitish in color, distinguished by a black patch along the outer margin.
- The egg stage of this species begins with a small, round form that exhibits a yellowish-white color. However, as it nears hatching, the egg darkens in color. Typically, these eggs are laid individually on the delicate portions of the plant.
- During the larval stage, the appearance of this species begins as yellowish-white to reddish-brown, with a dark brown to black head. Along the back, there are multiple rows of black bumps accompanied by short hairs, creating a spotted pattern. As the larvae mature, they can exhibit various colors ranging from brown, green, or black to pale yellow. Their bodies also feature dark grey stripes, and they measure approximately 40mm in length.
- The pupal stage of this species measures around 16-20mm in length. It has a shiny brown color and a smooth surface. At the posterior tip of the body, there are two parallel spines present.
Feeding & Damage
Among the different stages of the pest, the larva or caterpillar is the most harmful and destructive. It voraciously consumes leaves, growing points, buds, flowers, and even fruits, resulting in significant losses. The damage inflicted on leaves reduces the photosynthetic area, directly impacting the overall performance of the plant. Additionally, feeding on flowers hinders the formation of fruits.
The caterpillars are known to create circular holes in pods or fruits, penetrating inside to feed on the internal contents. They position their heads and foreparts inside the pod or fruit while leaving the rest of their bodies outside. These holes not only cause direct damage but also provide entry points for pathogens.
Multiple fruits/pods can be targeted by a single caterpillar.
Management & Control
There are multiple methods available for controlling the African Bollworm. Among these, the most widely used and effective approach is the application of chemicals, specifically insecticides.
The following insecticides have proven to be effective in controlling this pest.
- LEXUS 247SC 8ml/20l
- PENTAGON 50EC 10ml/20l
- KING CODE ELITE 50EC 10ml/20l
- LEGACY5% EC 10ml/20l
Please take note that whenever you are spraying, it is advisable to mix the insecticide with 3ml of INTEGRA per 20 liters of solution. INTEGRA acts as a sticker, spreader, and penetrator, thereby enhancing the effectiveness of the chemical being used.
To prevent the pest from developing resistance to any specific insecticide, it is recommended to alternate the chemicals used rather than relying on a single one throughout the entire season. In cases where the pest has infested the crop during the fruiting and harvesting stages, it is advisable to choose an insecticide with a shorter post-harvest interval for application.
The management of African Bollworm can also be achieved through the utilization of the following methods:
- Introduction of predators
- Practicing crop rotation with non-host plants
- Maintaining field hygiene
- Proper weed management in order to ensure the insect cannot hide in the weeds