Chalcodermus aeneus (Coleoptera: Curculionidae): Historical Pest Status, Potential for Spread, and Current Management

Abstract

The cowpea curculio, Chalcodermus aeneus Boheman (Coleoptera: Curculionidae), was first described from samples collected by Chevrolat in Mexico in 1837. Cowpea, Vigna unguiculata (L.) Walp. (Fabaceae), has nothing to do with the original hosts of this curculio species, because cowpea is from the Old World, specifically Africa, and C. aeneus has never been reported in the Old World. Cowpea curculio has been reported as a major pest of cowpea in the southeastern USA for well over a century. The distribution of C. aeneus in the US in 1910 was reported to be in the states of Texas, Louisiana, Alabama, Florida, Georgia, South Carolina, North Carolina, Oklahoma, Maryland, and Missouri. Outside of the US, C. aeneus is found in Mexico, Belize, Guatemala, Honduras, Nicaragua, and Peru. This curculio causes tremendous damage to cowpea, so much so that it can render cowpea production unsustainable in a curculio-infested region. Recent deficiencies in viable commercial insecticide controls have led to repeated collapses of acreage in Georgia. In experiments reported here, as much as 60% yield loss occurred with only moderate C. aeneus infestations. Heavy curculio pressure shut down cowpea production in our test, even with fairly effective foliar insecticides. Fortunately, C. aeneus is not easily transported in cowpea shipments around the world because it reproduces only in green pods, from which it leaves to pupate in the soil before the grain dries. This curculio can be quarantined effectively from large scale movement via shipping due to its reproductive biology, but spreads easily via a land to cowpea crop "bridge." In the southeastern US, research efforts are underway to identify means to reduce the overwintering populations, with the goal of regional eradication sometime in the future.