Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2002
Publication Date: 1/1/2003
Citation: ANDERSON, G.L., DELFOSSE, E.S., SPENCER, N.R., PROSSER, C.W., RICHARD, R.D. LESSONS IN DEVELOPING SECCESSFUL INVASIVE WEED CONTROL PROGRAMS. JOURNAL OF RANGE MANAGEMENT. 2003. v. 56. p. 1-12. Interpretive Summary: The use of biological agents to manage problem weed species is more than 100 years old(Gassmann 1996). The goal of biological control is to use diseases, parasites, or predators to increase the mortality of the problem weed species, thus reducing the plants ability to effectively compete with native vegetation (Krebs 1978). The success or failure of biological contro oprograms has typically been evaluated from the perspective of the agent- host interaction. Perhaps the quintessential definition of biological contr success is written by Lawton (1985). Lawton states, "The hallmark of successful biological control is a persistent, marked reduction in the pest population." Huffaker and Kennet (1969) outlined five principles that contirbute to the success of bibiological control agens: 1 general adaptati to the environment and the host, 2. High searching capacity, 3 high rate of increase relative to its host 4. General mobility adequate for dispersal 5 minimal lag effects in responding to host changes in numbers:. Given the above definition and the five principles for improving eh effectiveness of biological control agenst, the success of biological control programs is generally believed to be around 25-30% (Krebs, 1978, Myers 1985). Stated that "Different agents may be successful in different environments and successful control may only be achieved in certain environments.". Leafy spurge is now believed to infest two million hectares throughout 35 states and all the approved in the US for leafy spurge field releases have estab- lished. Yet, the best estimates of leafy spurge population change indicate that infestations are doubling every ten years and in some cases every five years. (Anderson et al.1999). Based on Lawtons (1985) definition and the above information we conclude that biological efforts to control leafy spg.
Technical Abstract: Leafy spurge (Euphorbia esula L.) Is a deep-rooted, perennial weed with erect stems 40-80 cmtall. The weed reproduces by both vegetative buds and the production of large quantities of seeds. A native of Eurasia, leafy spu was first reported in the state of Mass in 1827. Leafy spurge now occurs abundantly on the northern Great Plains of the US and the prairie provinces sof Canada, where it often forms stands dense enough to displace native plants and restrict cattle grazing. Biological control of leafy spurge in t US began in the 1960's with the introduction of Hyles euphorbia. Fifteen nonindigenous insect species have been approved for release in the US for the control of leafy spurge. Different biological control agents affect the leafy spurge plant indifferent ways. Primary methods of attack include consumption of above-ground plant material, consumption of root material and blocking seed production. Aphthona sp. Flea beetles have produced the greatest impact on leafy spurge. A. nigriscutis and aczwaliane/lacerto impact the plant by oviposint eggs at the base of the plant. The resulting larvae feed on leafy spurge roots, increasing plant morbidity, reducing pla health and creating pathways for the introduction of plant pathogens. Data collection indicates that flea beetles can reduce leafy spurge stem densiti by as much as 80%-90% over large areas. While leafy spurge continues to increase in the US, techniques for control-while still evolving-continue to improve. Measuring the success of biological control has traditionally been approached from the e perspective of agent/host interactions.Too often our perception of success or failure is predetermined by how we choose to view the problem. Multiple dimensions of success exist when one views the issue from a broader perspective. Evaluations on leafy spurge must be done.