2011 Annual Report
1a.Objectives (from AD-416)
1: Isolate and identify chemical factors responsible for host recognition and host acceptance by western corn rootworm larvae.
2: Evaluate the chemistry of alternate hosts and native sources of resistance in maize to WCR larval feeding for feeding stimulants and host-recognition factors and correlate their chemical profile with WCR behavior on these plants.
3: Evaluate potential applications of WCR larval feeding stimulants.
4: Evaluate feeding behavior of WCR larvae that are resistant to Cry3Bb1 transgenic corn on Bt and isoline corn.
1b.Approach (from AD-416)
A collaborative approach will be taken with Colorado State University (CSU). Aspects of the proposal having to do with chemical separations and identifications will be done at CSU along with most of the behavioral bioassays. Objective 4, all field work in Objectives 2 and 3, and insect rearing will be done by ARS in Columbia, MO. Aspects done at each location will be put together toward joint accomplishments.
This work is related to Objective 1 of the parent project: "Develop lines of the western corn rootworm resistant to transgenic corn and investigate the biology, pest/host interactions, and fitness costs of resistant and control colonies as they relate to resistance management and rootworm biology."
Seed mix "refuges" have recently been registered for commercial sale and are likely to become even more important as we move forward in delaying the evolution of resistance to transgenic corn expressing an insecticidal protein derived from a bacteria, Bacillus thurengensis (Bt) corn. However, in seed mix refuges, insect movement from plant to plant can sometimes speed the development of resistance. In order to understand the role of western corn rootworm larval movement in a seed mix scenario, a series of treatment combinations were evaluated in the field (all Bt corn, all isoline (non-transgenic control), isoline surrounded by Bt, and Bt surrounded by isoline corn). Each combination of Bt and isoline corn also had two types of rootworm infestations. Although Bt corn performed quite well in nearly all planting and infestation combinations, when surrounded by two highly damaged isoline plants, damage to Bt plants increased significantly due to larval movement from nearby isoline plants.