2007 Annual Report
The behavioral responses of Orius insidiosus with crop and non-crop plants Natural enemies of insect pests are frequently found to be more abundant in vegetationally diverse cropland than in pure monocultures, but the reasons for this trend are poorly understood. Orius insidiosus is a key predator of soybean aphid, and the reproductive and feeding behaviors on five different agronomically relavent crop and non-crop plants were examined. Our results clearly show that O. insidiosus populations are favored when low levels of weeds are allowed to persist in soybean fields. This trend is driven by an ovipositional preference for the weeds, coupled with higher survival of the immature stage of the insect. Orius insidiosus females do not show a response to plant volatiles, but make their reproductive decisions based on proximal cues present on the different plant species (specifically trichome densities and epidermal thicknesses). The result of this research clearly point out specific mechanisms that drive why this predator is more abundant in diversified cropland. Application of the research through allowing non-competitive weed populations to persist in cropland, or the use of cover or companion crops, will result in lower pesticide use and a stronger reliance on environmentally safe natural control methods. The research for this accomplishment was performed under the auspices of NP304 Program Component III – Plant, Pest, and Natural Enemy Interactions and Ecology and Problem Statement III.A. – Understanding Complex Interactions.
Soybean crop cultural practices for bean leaf beetle population management: Bean leaf beetle, an emerging soybean insect pest of great economic importance in the U.S., has three subterranean immature (larval) stages that feed on underground portions of soybean plants. Because bean leaf beetle larvae consume soybean root nodules, crop cultural practices that affect soybean nodulation may have the added function of reducing bean leaf beetle populations. In greenhouse and field studies, we investigated the impact of soil nitrogen management on soybean nitrogen relations and bean leaf beetle population dynamics. Our preliminary findings suggest that bean leaf beetle larvae obtained from soybean plants given nitrogen starter fertilizer were smaller than those obtained from plants that were not given starter fertilizer. Because the mechanisms mediating these interactions were not readily apparent, further research on the feeding behavior of bean leaf beetle larvae, as well as the mechanisms underlying the relationships between soybeans, nitrogen, and bean leaf beetle, is underway. Successful completion of this research, which will result in soil nitrogen fertilizer application recommendations for soybeans that will reduce larval feeding damage without using insecticides, will allow soybean farmers to decrease production costs and increase soybean yield, quality, and profitability. The research for this accomplishment was performed under the auspices of NP304 Program Component V – Pest Control Strategies and Problem Statement V.C. – Physical/Mechanical and Cultural Control.
Identification of soybean lines resistant to soybean aphid: The soybean aphid (SBA, Aphis glycines) has recently become a major pest of soybean in the U.S. Several millions of acres are sprayed annually for SBA control until alternative control methods such as resistant soybean lines are developed. Growth-chamber experiments were conducted to determine and characterize host-plant resistance to the soybean aphid, and these showed that soybean lines Dowling, PI 71506 and PI 230977 were resistant to SBA. Resistance to SBA in PI 230977 was characterized with high levels of antibiosis due to lowered frequency of reproductive maturity and reduced number of progeny compared to susceptible lines. Subsequently, this line has been used in crosses by the soybean breeder at South Dakota State University in order to breed soybeans with resistance to SBA. This accomplishment supports National Program 304, Component V - Pest Control Strategies, Problem Area VB – Breeding for Host Plant Resistance.
Identification of wheat and triticale lines resistant to bird cherry-oat aphid: The bird cherry-oat aphid (BCOA) is a worldwide pest of wheat. The research identified and characterized several wheat and triticale lines that may serve as sources of resistance to BCOA in wheat-breeding programs. The wheat breeder at Colorado State University crossed a BCOA-resistant triticale line with a Colorado wheat variety. Results from testing the wheat-x-triticale lines confirmed that triticale is a significant source of resistance to BCOA and identified crossing lines with resistance to BCOA, but further work is needed to understand and improve the transference of BCOA-resistance from triticale to wheat. In the future, resistant varieties may reduce economic loss from BCOA, and eliminate economic and environmental costs associated with aphicide use. This accomplishment supports National Program 304, Component V - Pest Control Strategies, Problem Area VB – Breeding for Host Plant Resistance.
Field screening maize germplasm for resistance to western corn rootworms Corn rootworms (Coleoptera: Chrysomelidae) are devastating pests of maize (Zea mays L.), and the root damage caused by larval feeding often leads to economic loss. Plant breeders are developing novel maize germplasm in the hopes of identifying lines with resistance to immature rootworms. We assessed the resistance of 10 experimental synthetic maize populations and four maize hybrids to western corn rootworm larvae in the field. Some of the experimental lines appeared to be tolerant to rootworm damage, while others had negative impacts on rootworm fitness. This research serves as a foundation for screening maize germplasm for resistance to northern corn rootworms, and provides insight into the mechanisms of plant resistance. This accomplishment addresses the NP304 Program Component V – Pest Control Strategies, Problem Area V.B. – Breeding for Host Plant Resistance.
Reproductive Biology of Corn Rootworms: Adult male and female corn rootworms are difficult to distinguish, which is an important criteria in describing reproductive behavior. We described a sexually dimorphic character in pest corn rootworm and bean leaf beetle in which males possess on one of either or both front and middle legs, a hairless ovoid patch that apparently facilitates maintenance of the mating posture of males upon the hardened forwings of females. This patch proved as reliable as the standard supra-anal plate character, which requires beetles to be knocked out, for establishing sex of these important crop pests. This morphological character will facilitate distinguishing adult male and female pest corn rootworm and bean leaf beetle and research on their reproductive biology in relation to insect refuge management to transgenic crops. The research for this accomplishment was conducted in relation to NP304 Program Component II – Biology of Pests and Natural Enemies (Microbes), Problem Area: IIA – Basic Biology.
Anderson, R.L., Stymiest, C., Swan, B., Rickertson, J. 2007. Weed community response to crop rotations in western South Dakota. Weed Technol. 21:131-135.
Anderson, R.L., Beck, D.L. 2007. Characterizing weed communities among various rotations in central South Dakota. Weed Technol. 21:76-79.
Elliott, N.C., Tao, F.L., Giles, K.L., Kindler, D., French, B.W., Greenstone, M.H., Shufran, K.A. 2006. Ground beetle density in Oklahoma winter wheat fields. Southwestern Entomologist. 31(2):121-128.
French, B.W., Hammack, L. 2007. Sexual Dimorphism in Basitarsae of Diabrotica and Cerotoma spp. (Coleoptera: Chrysomelidae). Annals of Entomological Society of America. 100:59-63.
Hesler, L.S., Haley, S.D., Nkongolo, K.K., Peairs, F.B. 2007. Resistance to Rhopalosiphum padi (Homoptera: Aphididae) in Triticale and Triticale-Derived Wheat Lines Resistant to Diuraphis noxia (Homoptera: Aphididae). Journal of Entomological Science. 42(2):217-227 (April 2007).
Magalhaes, L.C., French, B.W., Hunt, T.E., Siegfried, B.D. 2007. Baseline Susceptibility of Western Corn Rootworm (Coleoptera: Chrysomelidae) to Clothianidin. Journal of Applied Entomology. 131(4), 251-255.
Prischmann, D.A., Dashiell, K.E., Schneider, D.J., Hibbard, B.E. 2007. Field screening maize germplasm for resistance and tolerance to western corn rootworms (Coleoptera: Chrysomelidae). Journal of Applied Entomology. 131(6):406-415.
Riedell, W.E., Lundgren, J.G., Osborne, S.L., Pikul Jr, J.L. 2005. Effects of Soil Nitrogen Management on Soybean Nitrogen Relations and Bean Leaf Beetle Biology. Journal of Agricultural and Urban Entomology. 22(3&4):181-190.
Hesler, L.S., Dashiell, K.E., Lundgren, J.G. 2006. Characterization of resistance to aphis glycines in soybean accessions. Euphytica. 154:91-99.