Chinese bruchid

Callosobruchus chinensis L.

Coleoptera: Bruchidae

Chinese bruchid is distributed throughout the tropics and sub-tropics. It is the dominant pest species on legume seeds during post-harvest in Asia.

Host plants and damage

Chinese bruchid is a major pest of stored legumes. However, infestations by chinese bruchid also commonly occur in the field during seed formation, feeding on ripe seeds. Larvae are introduced from infested seeds into storage facilities where they feed and can cause substantial loss.

Preferred host plants are Vigna unguiculata (cowpea), Cajanus cajan (pigeon pea), Glycine max (soyabean), Cicer arietinum (chickpea), Lens culinaris ssp. culinaris (lentil), Vigna radiata (mung bean), Vigna angularis (adzuki bean), and Pisum sativum (pea).

In early stages of infestations, the presence of eggs cemented on pods is a symptom. Immature stages feed inside the seeds, and are not visible. Symptoms of advanced infestations are round holes in the seeds.

Morphology & biology

The adults of C. chinensis are 2.0-3.5 mm long. Elytra are pale brown and posterior parts are darker in colour with small median dark marks. Distinct patches of white setae cover the side margins of the abdomen. Adults live usually not longer than 12 days and do not feed on stored products. Females lay up to 70 eggs on legume pods and on seeds. The translucent, grey eggs have a flat base. They are glued firmly on food surfaces. The first instar larvae bores into a single seed were it develops. Larvae are white-yellow, grub-like and go through four ecdyses. Pupation occurs inside the seeds in an excavated chamber. The adults bore tunnels to seed surfaces and exit. A life cycle can be completed in 22-23 days under optimal conditions at 32 °C and 90 % relative humidity.

Monitoring

Advanced infestations of C. chinensis can be detected by the presence of hollowed seed cases with visible bore-holes. Larvae inside the seeds can be detected by cracking the kernels or by using x-rays.

Sticky traps, baited with the female sex pheromone, can be used to monitor adult populations.

Pest management

Biological control

There are several parasites described for Chinese bruchids, such as Anisopteromalus calandrae, Dinarmus basalis, and Lariophagus distinguendus. However, biological control has not been used for control of chinese bruchid in the field.

Cultural control

Store hygiene plays a major role in limiting infestation by Chinese bruchid. Remove infested residues from last season’s harvest.

Chemical Control

Fumigation with methyl bromide or phosphine during storage or treatments with organophosphates are used for chemical control. When small seed lots of pulses are stored, the admixture of vegetable oil can give good protection against Chinese bruchids.