Anitha Chirumamilla, Laurence Charlet, Brent Hulke, Gerald Seiler, Theresa Gross, Janet Knodel and Robert Knodel
Abstract: Breeding pest-resistance crop cultivars to insects and diseases is one of the primary goals of integrated pest management programs worldwide. Host plant resistance is a tactic that uses the plant’s own defenses to reduce injury from pest attack. Among the sunflower (Helianthus annuus L.) insect pests studied, the banded sunflower moth, Cochylis hospes Walsingham and the sunflower moth, Homoeosoma electellum (Hulst), are the two most important seed infesting moth pests causing significant yield losses in sunflower. The banded sunflower moth is more prevalent in the northern and central Plains whereas the sunflower moth is a more significant problem in the southern and central Plains. Cochylis hospes attacks the crop at an early stage of development and larvae feed on bract tissue, florets, developing achenes and mature seeds. Homoeosoma electellum larvae overwinter in the soil in Texas and adults migrate by northerly winds to the central and northern Plains. Female moths are attracted to and oviposit on blooming sunflower heads. Larvae feed initially on the florets and developing achenes and later destroy mature seeds. The goals of this research were to: 1) determine the mechanisms contributing to C. hospes resistance in previously evaluated resistant germplasm; 2) investigate the tactile effect of trichome density of the sunflower bracts on the ovipositional preference of the banded sunflower moth; and 3) evaluate sunflower germplasm for resistance to H. electellum. Our study showed that germplasm with potential resistance to the sunflower moth is being identified. Studies determining plant mechanisms conferring resistance to banded sunflower moth revealed that antixenosis is likely the predominant mechanism in the three tested resistant sunflower lines and either antibiosis or plant tolerance is the mechanism in the resistant check. Investigation of the role of sunflower bract trichome density in the ovipositional preference of adult C. hospes is in a preliminary stage and a detailed study including the potential influence of volatiles in attraction of moths to sunflower heads will be conducted in 2010.
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