African Boll Worm

Helicoverpa armigera

African Boll Worm, Tomato Fruit Worm, Corn Ear Worm, Gram Pod Borer, Tomato Grub, Old World Bollworm, Tobacco Budworm, Scarce Bordered Straw, Cotton Boll Worm

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An African Bollworm is a brown moth and a cosmopolitan pest, meaning it's now intercepted most of the continents. It is a major pest of cotton, but its larvae will also bore into the fruits and pods of Tomato, Maize, Sorghum, Chickpea, Pigeonpea and Groundnut plants. African bollworm is significantly important in terms of agriculture because it can dramatically reduce crop yields. In China, it only takes the discovery of three to five larvae to class the infestation as economically significant.

Traits

The larvae can make short work of the plants fruits, ultimately making them inedible.

Appearance

Adult moth: Colour varies significantly; the forewings are dull yellow, pale brown to reddish-brown. There is often an irregular brownish cross-band and a dark mark in the middle of each wing. The hind wings are paler, greyish-white. The hind margins are broadly marked with dark brown. Moths are about 15-20 mm long when at rest with a wingspan of 35-40mm. Pupa: Smooth and shiny brown. The length is about 15-20 mm with two short spines at the posterior tip of the body. Pupae are found in the soil, often directly under the plant. Larva: There are 5-6 larval instars. First instar larvae are about 1.5 mm in length and grow up to 3 mm; fully-grown larvae can reach up to 40 mm in length. Young larvae are generally yellowish to almost blackish. Older larvae often have dark stripes along the sides. They also have longitudinal white or beige stripes that extend along each side of the body. Egg: Shiny, yellowish-white at first, and become dark brown before they hatch. The shape of the eggs is spherical and about 0.5 mm in diameter. Eggs are laid singly usually on the upper side of leaves.

Symptoms

Caterpillars will eat the insides and outer surfaces of fruits. Black and brown lesions on fruit. Fruit may fall prematurely. Wilted leaves. Holes in leaves and petals. Stunted growth.

Activity

Nocturnal

Personality

Order

Lepidoptera

Family

Noctuidae

Metamorphosis

Complete

Distribution

Asia, Africa, Oceania, America and some parts of Europe.

Biological treatment

African Bollworm females are known to lay eggs on weeds. Furthermore, practising good housekeeping is essential in preventing an attack by this pest. Tidy borders and vegetable patches which are regularly weeded with sufficient gaps in between should make the area less appealing to a female moth. Likewise, annual ploughing or raking of soil beds at the end of the season will help to reveal any overwintering pupae. Picking off caterpillars and relocating them (or feeding them to the birds!) can be sufficient control if infestations are light. A mixture of pepper and marigold diluted with water are thought to deter bollworm. These moths have a natural enemy: Dejeania bombylans, a parasitic fly, commonly known as the bollworm fly. Attract these flies into the garden by replicating their favourite conditions. They favour veld grasses and broad-leaved herbs in the shade of bushveld trees. Trichogramma wasps are also known to parasitise bollworm eggs and can be attracted to the garden by planting a selection of indigenous flowering plants.

Chemical treatment

There are some suitable pesticides available on the market which may be of use for heavier infestations. Avoid using pesticides earlier in the year because, at this point, natural enemy numbers are low. Let their numbers increase and give them a chance to do their thing. Neem oils are supposedly more environmentally-friendly than synthetic pesticides. Bacterial sprays containing the B.t. Subspecies kurstaki is thought to be effective against this fly, although it can kill other small flies that weren't intended to be targeted.

Attracts

Other important host plants include rice, cowpea, okra, peas, field beans, soybeans, tobacco, potatoes, flax, Dianthus, Rosa, Pelargonium and Chrysanthemum.

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