NCERA - 125 Biological
Control of Arthropods & Weeds
State Reports for 2005
| Iowa - project reports |
| 1) Project Title: Natural enemy impact: Is soybean aphid regulation possible? Investigators: Nicholas Schmidt1,Matthew
O’Neal1, Jeremy Singer2, Keith Kohler2,
Contact: Matthew O’Neal (oneal@iastate.edu) Project Description: Recent evidence suggests the current community of natural enemies, can lower Aphis glycines population growth. During 2005, we investigated if natural enemies were limiting A. glycines establishment and subsequent populations in Iowa, and if this could be improved with habitat management. Specifically, natural enemy and soybean aphid abundance were compared for soybeans grown alone or with greater plant diversity. In 2005, we established in a randomized complete block design of soybeans grown alone or within an alfalfa stand managed as a living mulch. Although the alfalfa was cut and treated with herbicide to allow soybean establishment, no insecticides were applied. Populations of natural enemies and A. glycines were measured from May to September. Cages that excluded predators were used to determine the impact of natural enemies on A. glycines. On 17 June before natural populations of A. glycines had established, plots were artificially infested at 4 locations with 10 aphids with half of these covered with cages. Aphid populations were tracked in open and closed cages every 48-96 hours and cages were removed when alates were first noticed. Insect predators were observed throughout the growing season to feed on A. glycines, with the greatest concentration occurring in soybeans grown with alfalfa. The cage study indicates that when predators were excluded, A. glycines populations dramatically increased, > 3 fold within 72 hours. Greater aphid growth was seen on soybeans grown alone than combined with alfalfa. The combination of a top-down effect of insect predators or from a reduction in host quality, A. glycines populations were lowest on soybeans grown with alfalfa. We conclude that the current community of natural enemies in Iowa limits A. glycines establishment, and when increased through habitat management (i.e. a living mulch) a further reduction in A. glycines population is observed (Figure 1).
Figure 1: Aphid population in the presence (no cage) and absence (cage) of natural enemies in soybean plots grown alone (control) or with an alfalfa living mulch (alfalfa). Individual plants were infested with soybean aphids before natural infestations had occurred. 2) Project Title:Evaluation of reduced-risk insecticides for natural enemy conservation and soybean aphid management? Investigators: Matthew O’Neal and Wayne Ohnesorg; Department of Entomology, Iowa State University, Ames Iowa. Contact: Matthew O’Neal (oneal@iastate.edu) Project Description: We initiated a project to evaluate the compatibility of insecticides used in soybeans with a conservation or importation biolgocial control program. The products being tested include two seed treatments (Gaucho, Cruiser) comprised of unique active ingredients (imidacloprid, thiomethoxam respectively) and two foliar insecticides (Fulfill, Trimax) also comprised of two unique active ingredients (pymetrazione, imidacloprid respectively). These products have been selected based on their mode of contact (systemic) and in some cases their extreme selectivity for aphids. Included in this comparative study are a pyrethroid (Warrior) and an untreated check. By comparing the impact of these products to natural enemies and soybean aphids, we will determine if reduced-risk insecticides can be incorporated successfully with conservation of beneficial insects. During the 2005 growing season, we observed comparable impact to soybean aphids by these reduced-risk insecticides to more broad-spectrum insecticides (O’Neal et al. 2005, or visit http://www.ipm.iastate.edu/ipm/icm/issue/6030). We are currently analyzing data from the past growing season to determine the effects of these products against endemic natural enemies. For the Fall/Winter, laboratory research is planned to study the impact on Asia natural enemy species once they become available from quarantine labs in Minnesota and Delaware. Back to top of web page |
| Iowa - publications |
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Peer review: O’Neal, M.E., K. Mason, and R. Isaacs. 2005. Seasonal abundance of ground beetles in highbush blueberry (Vaccinium corymbosum) fields and response to a reduce-risk insecticide program. Environ. Entomol. 34: 378-384. Extension publications: Back to top of web page View reports from other state |
