Breeding Maize for Insect Pest Resistance

Abstract

In SSA, as in other parts of the world, insect pests live and/or feed on all parts of the maize plant, causing losses that reach millions of dollars annually. In terms of economic importance on maize in SSA, insect pests may be grouped into three: (i) stem and ear borers, armyworms, cutworms, and grain moths, all of which are lepidopterous insects; (ii) weevils, grain borers, rootworms, and white grubs, usually generally referred to as beetles; and (iii) aphids and leafhoppers, which are presently known as virus disease inciting insects. In terms of the damage they cause and available technologies to contain them, insect pests of maize are also grouped into three; that is, field pests (stem and ear borers, armyworms, silkworms, and leafhoppers), field-to-store pests (the most common example is maize weevil, Sitophilus sp.), and the storage pests (including the maize and rice weevils, Sitophilus zeamais Moench, S. oryzae L., and more recently, Prostephanus truncantus Horn). In SSA, genetic studies and breeding for resistance have been focused primarily on the field pests, particularly the stem and ear borers. In the mid-1980s, IITA established a borer rearing facility that made it possible to infest large numbers of lines and populations for screening purposes. Borer rearing facilities are also available at Kenya Agricultural Research Institute (KARI), Katumani, and the International Center for Insect Physiology and Ecology (ICIPE), Nairobi, Kenya. Maize breeders and entomologists have used these facilities to breed for borer resistance and minimize escapes during screening. In 2015, an unprecedented invasion of armyworm occurred in SSA and is presently a challenge to maize breeders and entomologists.