American bollworm
Namibian crop pests #29 
Helicoverpa armigera Order: Lepidoptera Family: Noctuidae

 

Imago, yellow-brown form


Imago, the grey form


Imago, grey form
Caterpillars on pearl Millet head
 
 

 Caterpillar on beans

COMMON NAMES

okapuka (general name) (Oshikwambi, Oshikolonkadhi); okalombo (general name) (Oshindonga,  Oshikwambi, Oshingandjera, Oshimbalantu, Oshikwaluudhi ,Oshikolonkadhi); Amerikaanse bolwurm (Afrikans) 

PEST STATUS

American bollworm is present in all four regions of north central Namibia on most field and garden crops, but it seldom reaches levels at which it causes serious damage. American bollworm is found on a wide range of hosts, from rain-fed cereal crops to legumes and many vegetable crops. In Namibia it is especially noticable on pearl millet (Pennisetum glaucum) heads at the flowering stage, on maize cobs and on pods of beans and other legumes. It is often a severe problem on tomato in irrigated gardens. 
Caterpillars of American bollworm may be found throughout the year. The bollworm caterpillars are scattered in the fields and do not occur in dense outbreaks. 

DESCRIPTION

The colour of American bollworm caterpillar is so variable that identification may be difficult. The caterpillar is best recognised on the large size of 30-40 mm, the fine hairs and the clear stripes along the side of the body. The caterpillar does not occur in clusters. Most other caterpillars in northern Namibia do not have these characteristics. 
The adult moth has two distinct forms, one has grey front wings while the other is yellow brown. The dark spots on the front wings often form a V shaped mark. The hindwings are dull grey with a dark edge. The wingspan is up to 40 mm. 

CONTROL

Control of American bollworm is not recommended for most farmers. Usually only few caterpillars are seen on crops, and potential damage is often overrated. The caterpillar is large and easy to find on pearl millet. Hand picking is therefore a practical option. 
Control should only be considered in special cases where a valuable cash crop is regularly attacked by bollworm caterpillars. If chemical control is found necessary, please contact the FSRE pest officers for precise advice on chemical control. The contact numbers and addresses are listed on the cover. 
 

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