|Chirumamilla, Anitha - North Dakota State University|
|Knodel, Janet - North Dakota State University|
|Charlet, Laurence - Retired ARS Employee|
|Foster, Stephen - North Dakota State University|
|Ode, Paul - Colorado State University|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2013
Publication Date: 2/1/2014
Citation: Chirumamilla, A., Knodel, J.J., Charlet, L.D., Hulke, B.S., Foster, S.P., Ode, P.J. 2014. Ovipositional preference and larval performance of the banded sunflower moth (Lepidoptera: Tortricidae) and its larval parasitoids on resistant and susceptible lines of sunflower (Asterales: Asteraceae). Environmental Entomology. 43(1):58-68. DOI: 10.1603/EN13157.
Interpretive Summary: Banded sunflower moth is a species of insect that causes economically important levels of damage to seed produced in sunflower fields. This work provides insight into the relationship between genetically unrelated sunflower lines and the preference of the banded sunflower moth to lay eggs, develop into larvae, and cause damage to developing sunflower seeds. Since lines with known susceptibility and resistance to the insect are used, the expectation is that egg counts, larval counts, rates of parasitism by other insects, and damage assessments on sunflower seed will be different among the lines. In addition, diterpenoid content, which has been shown to affect insect behavior, was assessed for each of the lines. The damage ratings fell into the expected resistant and susceptible categories, but the resistant lines did not always have the lowest egg or larval numbers. Diterpenoids were not significant cofactors except for in the damage assessment of the sunflower seed. This work provides a framework in which to develop an action plan for insect resistance research in sunflower.
Technical Abstract: Banded sunflower moth, Cochylis hospes Walsingham, is one of the most destructive seed-feeding insect pests of sunflowers, causing significant economic yield losses in the northern Great Plains. In an attempt to understand host-plant resistance mechanisms for this pest, we field tested over several years the effects of seven sunflower accessions, rated as resistant to C. hospes in previous screening trials, and a susceptible control (Par 1673-2), on the ovipositional preference and larval performance of C. hospes and its larval parasitoids. Of the resistant accessions, PI 494859 was the most preferred for oviposition, receiving a significantly greater number of eggs per head than did the susceptible Par 1673-2 in two out of three years. However, the number of larvae, and consequently the rate of seed infestation, found in PI 494859 heads were significantly lower than those in Par 1673-2 heads over all three years. Female moths laid relatively few eggs on accessions PI 170385, 291403, and 251902, compared to on Par 1673-2, resulting in lower numbers of larvae per head and lower percentages of seed damaged. No association was observed between the concentrations of two diterpenoid alcohols or two diterpenoid acids in sunflower bracts and the numbers of eggs laid on the heads of the accessions. A positive association between resistance to larval feeding and parasitism was found in years 2006 and 2008, with resistant accessions having significantly greater proportions of parasitized larvae than did the susceptible Par 1673-2.