African black beetle in horticulture

Page last updated: Tuesday, 26 October 2021 - 7:21am

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Pest status

African black beetle is primarily a grass-favouring, pasture-dwelling insect.

As such, most of its pest status in horticulture results from planting crops in infested pasture.

Because of the beetle’s strong flight activity, crops may become infested when the beetles disperse. Less commonly, crops may be infested along edges after beetles walk into a crop from adjacent infested pasture.

Where irrigation is used in horticultural crops, the higher survival rate for larvae in summer may lead to greater damage from both larvae and subsequently adults.

African black beetle adults can kill plants by feeding on the stem at ground level
African black beetle adults feeding on the stem of a grapevine
Foliage of red grape variety damaged by stem damage from African back beetle adults turns red prematurely
Red grape variety damaged by African black beetle
Potato plants wilt after the stems are attacked at ground level by African black beetle adults
Wilting potato stems caused by feeding at ground level by African black beetle

Adult beetles feed on plant stems near the soil surface. This occurs in vineyards, fruit and truffle orchards, olive groves and newly emerging vegetables such as potatoes and vegetable brassicas.

In vineyards, the foliage of red grape varieties attacked by beetles turns red prematurely. In white grape varieties, foliage of damaged vines turns yellow. Young stems in potato crops wilt and die.

Potato tubers with deep holes from feeding damage by African black beetle adults are rejected at market
Damage to potato tubers by African black beetle adults

As well as affecting plant establishment, adult beetles can feed directly on the harvestable portions of crops. This applies to potato tubers and occasionally truffles.

Potato tubers with deep holes from feeding damage by African black beetle larvae are rejected at market
Damage to a potato tuber by the larval stage of African black beetle

Larvae are true soil insects, feeding on organic matter and below-ground parts of plants. 

Larvae are less damaging than the adults, and  rarely damage crops or pasture. However, they can damage potato tubers if crops of appropriate maturity coincide with the presence of mature larvae - December to January.

Larvae feeding on the roots of turf result in dead patches in lawns.