Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/17/2007
Publication Date: 3/8/2008
Citation: Oyediran, I., French, B.W., Clark, T.L., Dashiell, K.E., Hibbard, B.E. 2008. Prairie grasses as hosts of the northern corn rootworm (Coleoptera: Chrysomelidae). Environmental Entomology. 37(1):247-254. Interpretive Summary: The registration of transgenic corn with resistance to corn rootworm larval feeding offers a viable alternative to insecticides for managing the most economically important insect pests of corn. Maintaining susceptibility to transgenic crops (resistance management) is in the interest of growers, the Environmental Protection Agency, and industry, but requires an understanding of corn rootworm biology (such as larval use of alternate hosts) that does not currently exist. We evaluated 27 prairie grass species thought to be among those dominant 200 years ago in the northern Midwest as larval hosts of the northern corn rootworm along with three control species. Ten prairie grass species were not significantly different than maize in term of percentage larval recovery and growth in head capsule width. This information will be important to seed companies, the Environmental Protection Agency, and modelers in their attempts to develop resistance management plans for transgenic corn.
Technical Abstract: We evaluated 27 prairie grass species thought to be among those domi-nant 200 years ago in the northern Midwest as larval hosts of the northern corn rootworm, Diabrotica barberi Smith and Lawrence. Maize (Zea mays L.), spring wheat (Tritcum aestivum L.), and sorghum (Sorghum bicolor L.) were included as controls for a total of 30 species evalu-ated. Twenty pots of each test species were planted and each pot in-fested 5 weeks later with 20 neonate northern corn rootworm larvae. Two pots within each of five replications were assigned a sample date for larval extraction. The remaining pot from each replication was used to monitor adult emergence. The contents from assigned pots were placed in Tullgren funnels equipped with 60 W lights for larval extraction 7 or 14 d after infestation. The percentage of larvae recovered, larval head capsule width and average dry weights varied significantly among the grass species. The highest percentage of larvae was recovered from slender wheatgrass, Elymus trachycaulus (Link), and this was signifi-cantly greater than the percentage recovered from maize for the second sample date. Western wheatgrass, Pascopyrum smithii (Rydb.), Canada wildrye, Elymus canandensis L., redtop, Agrostis gigantean Roth, Buf-falo grass, Bouteloua dactyloides (Nutt.), spring wheat, Triticum aes-tivum L., pubescent wheatgrass, Elytrigia intermedia (Host), Indian grass, Sorghastrum nutans (L.), big bluestem, Andropogan gerardii Vit-man, and bottlebrush grass, Elymus hystrix L. were also relatively good hosts in that the percentage of larvae recovered from these species was not significantly different from maize when sample dates were combined. These same ten species were also not significantly different than maize in the combined analysis for change in head-capsule width. The average dry weight of larvae recovered was significantly greater for slender wheatgrass than for all other species except maize 14 d after infesta-tion. Average dry larval weight for larvae recovered from all species was significantly less than dry larval weight for larvae recovered from maize. Overall, adults were produced from only 5 of the 28 species evaluated and no analysis was performed because of the low numbers. The results from this study are discussed in relation to the potential of alternate hosts of northern corn rootworm in resistance management of transgenic maize.