Scientific Name: Acanthoscelides obtectus Say
Common Names: Bean Weevil
Synonyms
Bruchidius obtectus
Bruchus obtectus
Laria obtectus
Taxonomic Position
Class: Insecta
Order: Coleoptera
Family: Bruchidae
Genus: Acanthoscelides
Species: Acanthoscelides obtectus
Geographical distribution
USA and Canada, Central and South America, Europe and Northern Asia, Mediterranean Basin, Africa, South and South-East Asia, Australasian - Oceanian, Cosmopolitan
Host Range
Pigeon pea, Phaseolus (beans) and stored pulses
Pest Destructive Stage
Primary pest
Eggs –laid or stuck individually onto seed or pod
Larvae – immobile, concealed within seed
Adults – do not feed on commodity, fly readily
Identification Features -
Adult
- The adult is 3-4.5 mm long.
- The main colours of the body are greys, browns and reddish-brown, without any distinctive patterns.
- The antennae are dark grey except for segments 1-5 and 11, which are reddish.
- The abdomen is reddish; the legs are reddish, except for the ventral half of the hind (and sometimes the middle) femur which is black.
- Each hind femur has, on the inner ventral ridge near the apex, a large tooth followed by two or three smaller, sharp teeth. (Inner ridge of ventral margin of hind femur with 3 or 4 teeth)
- The setae of the prothorax and elytra are mainly yellowish-grey with darker brown patches.
- In male the pygidium is vertical and only partly visible from above; in females it is oblique and fully visible from above.
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Adult – Dorsal View
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Hind Leg – single large teeth followed by two small teeth
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Pygidium
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Life Cycle
The eggs are laid loosely, but are often lodged under cracks in the bean testa. Infestation may begin in the field, where eggs are laid on ripening pods. Although optimum conditions for development are around 30°C and 70% RH, the species is nevertheless capable of surviving at low temperatures and will breed slowly at 18°C.
Detection methods
Samples can be examined with naked eye or under magnifying glass or stereoscopic binocular microscope and by using soft X-ray and seed transparency method hidden infestation can be detected.