Comparative host selection and reproductive physiology for sunflower moth, Homoeosoma electellum (Hulst) (Lepidoptera: Pyralidae), and banded sunflower moth, Cochylis hospes Walsingham (Lepidoptera: Tortricidae)

Sunflower moth, Homoeosoma electellum (Hulst), and banded sunflower moth, Cochylis hospes (Walsingham), are major pests of cultivated sunflower, Helianthus annuus L. The effect of adult age on mating, and of adult age and female multiple mating on reproductive output were investigated. In both species, male and female age had significant effects on mating, with a significantly smaller percentage of 1-d-old adults copulating or a significantly smaller proportion of 1-d-old males transferring a spermatophore than for older females. One-day old adults (for both sexes) of both species also tended to copulate later in the scotophase than comparable older adults. Female age at first mating also had a significant effect on fecundity and fertility in both species; fecundity and fertility tended to decrease with increasing age at first mating. It appears likely that H. electellum females use chemical differences between the two different stages of sunflower heads in order to distinguish between them. C. hospes females use volatile chemicals from the sunflower head for hostfinding, and use contact and possibly volatile chemicals from heads for host acceptance, too. It was also demonstrated that the presence of conspecific larvae resulted in reduced oviposition by the respective females. In addition to female preferences to the respective head stages, neonate larvae for both species exhibited preference for tissue associated with head phenology. Thus, H. electellum neonate larvae preferred florets from R5 heads over bracts from R2 heads while C. hospes neonate larvae preferred bracts from R2 heads over florets from R5 heads.;We tested the preference-performance hypothesis for the sunflower moth, H. electellum, on 17 sunflower germplasm lines. Lines were selected to give a range covering those used in breeding for yield and those used for insect or disease resistance. In binary choice tests, using a standard control line, females showed a range of preference responses to the lines. Performance on the 17 lines, tested by infesting each of the heads with 20 neonate larvae and recording the number of pupae obtained and their individual weights, also varied among lines. Female preference and larval performance (both in terms of percentage of larvae reaching the pupal stage and pupal weight) were positively correlated, indicating that females tended to choose plants on which larvae performed better.