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"Ecological Barriers for the Establishment and Population Increase of Flea Beetles on Leafy Spurge"

 Bob Nowierski

Question 1. What major problem or issue is being resolved and how are you resolving it?

The major problem being resolved in our research concerns ecological barriers that may negatively affect the establishment and population increase of the five flea beetle species released against leafy spurge. We are helping to resolve this problem by addressing the following research areas:

A. Determining the habitat associations of the flea beetles to improve their chances for establishment and impact on leafy spurge.

B. Evaluating the genetic variability of leafy spurge and the five Aphthona species, and the influence of such variability on flea beetle performance.

C. Determining the ecological amplitude of leafy spurge.

D. Determining the sex ratios among different populations of five flea beetle species and possible causes of the female-biased sex ratios.

E. Determining the flea beetle impact on plant species diversity and species richness.

Question 2. How serious is the problem? Why does it matter?

The problem is very serious, as approximately 1/3 of the flea beetle releases fail to establish. Because the flea beetles are an effective means of controlling leafy spurge in certain areas, lack of establishment and impact can be of major economic importance, particularly for extensive areas of infestation, or sensitive areas infested by leafy spurge where herbicide use may be cost-prohibitive or undesirable.

Question 3. How does it relate to the National Program(s) and National Program Component(s)?

The TEAM Leafy Spurge project is a part of the USDA/ARS Area-Wide Management Program. It is a component of Crop and Commodity Pest Biology, Control and Quarantine (304). TEAM Leafy Spurge complements efforts to develop new and improved pest control technologies and assess component technologies for integrated pest management (IPM) systems.

Question 4. What was your most significant accomplishment this past year?

The major problem being resolved in our research concerns ecological barriers that may negatively affect the establishment and population increase of the five flea beetle species released against leafy spurge. Flea beetle habitat association models developed from European data were compared statistically with similar models developed from U.S. data (obtained from 48 TEAM Leafy spurge research sites). European and U.S. habitat association models of the flea beetles were found to be statistically similar (P > 0.05). This means that had pre-release habitat association studies been conducted in the native range of the flea beetles they could have correctly predicted the habitats and site requisites in which they have been most successful in establishing in and having an impact on leafy spurge.

Question 5. Describe your major accomplishments over the life of the project, including their predicted or actual impact.

DNA was extracted from leafy spurge collected from 48 TEAM Leafy Spurge research sites. Procedures were worked out to consistently obtain Amplified Fragment Length Polymorphism (AFLP) data from any given leafy spurge sample with reasonable reproducibility. Twenty initial populations were chosen to begin answering questions on the level of genetic diversity present within and among leafy spurge populations. Current results from using several different primer sets on these populations indicate that there is relatively little polymorphism either within or among spurge populations.

DNA extraction techniques were developed for the five Aphthona species. Protocols are being developed to assess the genetic diversity of the flea beetle species within and among populations using AFLP analysis. Ninety-five populations (1396 individuals) of A. nigriscutis, A. lacertosa, and A. flava were screened for the presence of the intracellular bacterium Wolbachia. Wolbachia was detected in at least one female in 85.3% of the female populations of A. nigriscutis. In contrast, Wolbachia has not been detected in male populations of A. nigriscutis or males and females of A. lacertosa and A. flava. The results from preliminary statistical analyses suggest that Wolbachia infection levels are positively correlated with sex ratios among populations.

A. Spurge and soil samples were collected from 48 research sites in Montana, North Dakota, and Wyoming in 1998. Micro-and macro nutrients and physical properties were analyzed for the soil; micro- and macronutrients were analyzed for the leafy spurge foliage and roots.

B. Cover levels of spurge, grasses, forbs, shrubs, and bare ground were estimated from the 48 TEAM Leafy spurge research sites.

C. DNA analyses were conducted on leafy spurge from a number of the 48 TEAM Leafy spurge research sites.

D. Isozyme analyses were completed on flea beetles obtained from these research sites so that they could be identified; their relative frequencies and abundances were then determined.

E. Habitat association models were developed for the five flea beetle species relating their relative abundances to site requisites including chemical and physical properties of the soil, chemical properties of the spurge roots and foliage, and total plant cover. Habitat association models of the flea beetles developed from European data were validated with independent data collected from the 48 TEAM Leafy spurge research sites. European and U.S. habitat association models were found to be statistically similar.

F. Sex ratios were determined for nearly 300 flea beetle populations of A. cyparissiae, A. flava, A. lacertosa, and A. nigriscutis. DNA probes confirmed the presence of the Wobachia bacterium in Aphthona nigriscutis, the flea beetle species that has the most female-biased sex ratios compared to the other four flea beetle species released in North America. This organism may be responsible for male mortality, which may result in female-biased sex ratios.

G. Data were collected from four sites (two in MT and two in North Dakota) in 1999 and 2000 concerning the impact of flea beetles on plant species diversity and species richness. Data collection included: soil core samples (for micro- and macro-nutrient analyses and physical properties); flea beetle sweep counts; plant cover estimates of spurge, shrubs, grasses, and bare ground; and relative frequencies and densities of individual plant species. Preliminary results suggest that depression of spurge from flea beetles at relatively high spurge density sites may have a positive effect on plant diversity, plant species richness, and grass productivity in the beetle impact areas.

H. DNA extraction techniques were developed for the five flea beetle species. The initial steps of AFLP analysis (restriction, ligation, fluorescent tagging, and pre-amplification) have nearly been completed.

Question 6. What do you expect to accomplish year by year, over the next three years?

A. Finish assessment of the genetic variability of leafy spurge and the flea beetles species across the 48 TEAM leafy spurge research sites and relate such potential variability to flea beetle performance and establishment success (yrs. 1-2).

B. Develop an ecological amplitude model of leafy spurge based on information obtained from flea beetle control plots and sites where flea beetle failed to establish (yr. 1).

C. Evaluate infection levels of Wobachia among flea beetle species and among populations within species; determine if Wobachia infection negatively affects reproduction and contributes to the female-biased sex ratios found in A. nigriscutis and possibly some of the other Aphthona species (yrs. 1-2).

D. Obtain a better understanding of flea beetle impact on plant species diversity and species richness through completion of data analysis from the four Montana and North Dakota research sites (yr. 1).

Question 7. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology?

Results of isozyme analysis of the flea beetles have been published which allows the correct identification of Aphthona cyparissiae, A. flava, A. nigriscutis, and A. lacertosa. Isozyme patterns were also obtained for A. czwalinae, which enables us to distinguish this species from the other four flea beetle species. Flea beetle habitat association models developed from European data have been discussed in scientific forums and submitted for publication.

Now that the flea beetle habitat association models developed from European data have been validated from independent data collected from the 48 TEAM Leafy spurge research sites, an extension publication now can be generated that will identify the most appropriate habitats and phenological times for release of the various flea beetle species.

Question 8. List your most important publications in the popular press (no abstracts) and presentations to non-scientific organizations, and articles written about your work (NOTE: this does not replace your peer-reviewed publications which are listed below).

Nowierski, R. M. Biological control of weeds. Gave keynote presentation at the 50th Anniversary of the Broadwater Conservation District, Townsend, MT, February, 1997. 100 people attended.

Flaherty, C., and R. M. Nowierski. 2000. Finding a home on the range - for beetles. MSU News Services. Article written about flea beetle habitat association models developed from European and U.S. (TEAM Leafy spurge) data. Article published in numerous Montana Newspapers in June, 2000.

Nowierski, R. M. 2000. Biological control of leafy spurge, spotted knapweed, and Dalmatian toadflax. Forty minute invited presentation to growers and state and federal land management practitioners. 70 people attended. July 20, 2000, Hobson, MT.

Nowierski, R. M. 2000. Rangeland weeds of Gallatin County and integrated weed management. Presentation to Gallatin County Commissioners and general public interested in weed management issues. 40 people attended. March 10, 2000, Gallatin County Fairgrounds Extension Office.

Nowierski, R. M. 1998. Biological Control of Leafy Spurge. Talk presented at North Central Branch of the Entomological Society of America. Sioux Falls, SD, March, 1998.

Nowierski, R. M. 1998. Biological control of weeds in the U.S. and Canada: testing and releasing new biocontrol agents; new biological weed control targets. Talk presented at USDA-FS Western Forest Insect Work Conference. March, 1998.

Nowierski, R. M. 1998. Biological Control of Leafy Spurge: Problems and Prospects. Talk presented at Montana Academy of Sciences Symposium on Exotics in our Ecosystems, April, 1998.

Nowierski, R. M. 1998. Habitat Associations of Biological Control Agents of Weeds. Talk presented at W-185, Western Regional Committee on Biological Control in Pest Management Systems of Plants. October, 1998.

Nowierski, R. M., Z. Zeng, D. Schroeder, A. Gassmann, and M. Cristofaro. 1999. Habitat analysis of Euphorbia species and associated flea beetles in the Aphthona complex from Europe: Contributions of ecological studies to biological control, p. 54. In: Abstracts. Evaluating Indirect ecological effects of biological control, Int. Organ. Biol. Control, October 17-20, 1999, Montpellier, France.

Kazmer, D.J. and R.M. Nowierski. 1999. Occurrence of Wolbachia and female-biased sex ratios in Aphthona flea beetles introduced for biological control of leafy spurge. 1999 Annual Meetings of the Entomological Society of America, Atlanta, GA.

Nowierski, R. M. 2000. Habitat analysis of Euphorbia species and associated flea beetles in the Aphthona complex from Europe. Fifty minute presentation to weed lunch bunch, Montana State University. Twelve people attended. February 7, 2000.

Nowierski, R. M. 2000. Habitat associations of biological control agents of weeds. Invited talk emphasizing habitat associations of flea beetles on leafy spurge, Pacific Entomology Conference, Honolulu, HI, February 21-23, 2000.

Nowierski, R. M. 2000. Habitat analysis of Euphorbia species and associated flea beetles in the Aphthona complex from Europe: Contributions of ecological studies to biological control. Lincoln distinguished lecturer, University of Arkansas, Fayetteville, AK, April 21, 2000.

Question 9. Scientific publications

Nowierski, R. M., Z. Zeng, D. Schroeder, A. Gassmann, B. C. FitzGerald, and M. Cristofaro. (Submitted). Habitat Associations of Euphorbia and Aphthona Species from Europe: Development of Predictive Models for Natural Enemy Release Using Ordination Analysis. Biological Control.

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