Trap Crops: How Far We Are From Using Them in Cereal Crops?

Trap crops are plants grown along with the main crop in order to manipulate insect behavior to manage the insect pests and are used as a cultural management strategy in several crops. Trap crops also provide habitat to natural enemies and can reduce the need for insecticides and hence reduce the development of insecticide resistance. The attractiveness of the trap crop, the timing of planting, and the space it occupies are major factors to consider before selecting and using a trap crop. The addition of semiochemicals and incorporation of stimulo-deterrent diversion' can increase the efficiency of trap crops. The important insect pests of cereal crops reported to managed by using trap crops include the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), on wheat and the stem borers Chilo partellus (Swinhoe) and Busseola fusca (Fuller) on maize and sorghum. Other insect pests such as soil-dwelling wireworms [Agriotes obscurus L., Limonius californicus (Mannerheim) (Coleoptera: Elateridae)] on potatoes and the aphids Schizaphis graminum (Rondani) (Hemiptera: Aphididae), and Rhopalosiphum padi L. on wheat and the brown planthopper Nilaparvata lugens (Stal) on rice are also possible to manage by using trap crops. Cereal crops such as maize and wheat are sometimes themselves used as trap crops, yet there have been only a handful of attempts made to use trap crops in cereal crops. The major limiting factors in using trap crops in cereal crops are environmental conditions, variation in landscape and cultivation practices. Nonetheless, trap crops remain an important tool of integrated pest management, and future studies should work to improve the efficacy, cost efficiency, and availability of alternative trap crops for use in cereal cultivation.