Principles of agroecological management of maize pests

By Grace Kinyanjui

Maize is targeted by several pests, which cause significant yield losses. The most damaging pests are the caterpillars (larvae) of Fall armyworm and other night-flying moths such as African armyworm, cutworms, and African maize stalk borer. Other important pests include spotted stem borers, maize beetles, earworms, leafhoppers (vectors of maize streak virus), and aphids (vectors of maize dwarf mosaic virus). These insects attack different parts of the plants and their feeding damages can be observed on the leaves, whorls, stalks, tassels, and ears. The Fall armyworm, for instance, attacks all stages of plant development including seedling, vegetative, flowering, and ear formation with crop losses reaching up to 100%.

Pest problems on maize farms can be managed using “ecological pest management” strategies, which focus on the principles of agroecology. The key agroecological principles that are directly applicable to pest management include input reduction, biodiversity, and soil health.

The three principles of agroecology are further translated into practices that can potentially contribute towards sustainable pest management. Given that no single tactic can effectively manage insect pests, the best practices are integrated to develop an ecologically-based pest management toolbox.

Agroecological approaches harness nature-based solutions and form the pillars of organic farming. These approaches can be implemented in maize fields together with other essential pest management practices, listed below, for reduced pests’ infestations and optimal crop yield.

• Regular monitoring of maize fields from the seedling stage to allow early detection of pest populations and infestations. Monitoring of armyworms and stemborers can be done using pheromone traps. Crop scouting can be done for all maize pests by checking feeding damages such as defoliated leaves, dead hearts and the presence of frass and holes on plant parts.
• Use of flower-rich field margins in maize monocrops to provide food and harborage for natural enemies. Intercrops of maize and legumes are highly encouraged because maize monocrops encourage biodiversity loss.
• Cultural practices such as good crop hygiene, proper weed management to enhance crop vigour; handpicking and destruction of egg masses and caterpillars.
• Homemade biopesticides reduce infestation of many insect pests. Examples include plant extracts of neem, wild marigold, chili pepper, and Tephrosia vogelii. Application of ash or dry soil into the leaf whorls of young plants can also suffocate the hiding caterpillars.
• Commercial microbial biopesticides for fall armyworm include MAZAO ACHIEVE from Real IPM Company (K) Ltd and HALT NEO from Osho Chemical Industries Ltd.
• Release of parasitoids into the maize fields to parasitize eggs and larval stages of specific pests. For instance, Trichogramma, Telenomus, and Cotesia species target Fall armyworm. Mass rearing of these parasitoids is done by the International Centre of Insect Physiology and Ecology (icipe) and the Dream Team Agro Consultancy Limited.