Discovery and Evaluation of Biological Control Agents of Medusahead Rye and Other Important Weeds of Western U.S. Rangelands
Great Basin Rangelands Research
2011 Annual Report
1a.Objectives (from AD-416)
Search for candidate biological control agents of exotic, invasive weeds of the western U.S. in the Mediterranean Basin and central Asia and study the candidates’ host-specificity and impact on the target weed.
1b.Approach (from AD-416)
Natural enemies (e.g. herbivores, pathogens) will be collected on target weeds in their native range. Characteristics of the natural enemy infestation, such as relative abundance, phenology, and impact on the target weed will be recorded. Natural enemies will be reared and identified by taxonomic specialists and assessed for their potential as biological control agents through host-specificity testing on non-target plant species. A list of test plant species for medusahead rye biological control candidates has been developed and submitted to TAG (USDA-APHIS Technical Advisory Group). The primary goal of this SCA is to discover and develop candidate biological control agents that are highly host-specific and damaging to medusahead rye.
This agreement was established in support of Objective 1 of the parent project in order to facilitate the goals of this objective related to foreign exploration for weed biological control agents. Progress of the cooperator’s research was monitored via regular telephone and electronic mail correspondence, as well as a face-to-face meeting at a scientific conference. Field surveys to date in Armenia, Bulgaria, China, Iran, Kazakhstan, Turkey, and southwestern Russia have identified several candidate agents that have undergone preliminary host-range testing and merit further investigation (e.g. development of mass-rearing methods and assessment of impact to the target weed). Those with continued promise for potential importation and release include the weevils Melanobaris sp. n. pr. semistriata and Ceutorhynchus marginellis, the leaf beetle Phyllotreta reitteri, the stem-mining fly Lasiosina deviata, and the mite Metaculus lepidifolii. More than a dozen other arthropod and pathogen species have been recorded on perennial pepperweed (Lepidium latifolium) but were eliminated from consideration in preliminary host-range testing. Two rust fungi were recently found in Turkey on cheatgrass (Bromus tectorum) and L. latifolium but have yet to be tested. Rust fungi are generally considered very promising for classical biological control due to their high host-specificity and rapid dispersal.