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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 its influence 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 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) to which it has been assigned?

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 were the most significant accomplishments this past year?

The relative frequency and abundance of five flea beetle species from 48 TEAM leafy spurge research sites were determined from field collections and isozyme analysis. Habitat association models were developed that relate the five flea beetle species to site requisites, including chemical/physical properties of the soil, chemical properties of the spurge foliage and roots, and total plant cover.

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

a.    Spurge and soil samples were collected from 48 research sites in Montana, North Dakota, and Wyoming. 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.    Preliminary genomic DNA and Phylogeographic DNA analyses were conducted on leafy spurge from some of the 48 research sites.
d.    Isozyme analyses were completed on flea beetles obtained from these research sites so that they could be identified (Figure 1); their relative frequencies and abundances were then determined (Table 1).

e.    A preliminary habitat association model was developed for the five flea beetle species relating the relative abundance of flea beetles to site requisites including chemical and physical properties of the soil, chemical properties of the spurge roots and foliage, and total plant cover.

f.    Sex ratios were determined for over 200 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 (three in MT and one in North Dakota) concerning the impact of flea beetles on plant species diversity and species richness.

Question 6. What do you expect to accomplish, year by year, over the next 3 years?

a.    Validate flea beetle habitat association models developed from European data with models developed from plant, soil, and insect data collected from the 48 TEAM leafy spurge research sites (yr. 1).

b.    Validate flea beetle habitat association models developed from 48 TEAM leafy spurge research sites with independent plant, soil, and insect data collected by the TEAM leafy spurge assessment team from the 1999 and 2000 field seasons (yr. 2).

c.    Gain a better understanding of flea beetle impact on plant species diversity and species richness independent of year to year differences in temperature and moisture levels (yrs. 1-2)

d.    Finish assessment of the genetic variability of leafy spurge across the 48 TEAM leafy spurge research sites and the influence of such variability on flea beetle performance; evaluate flea beetle performance on native Euphorbia species (yrs. 1-3).

e.    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. 1-3).

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 products?

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 where also obtained for A. czwalinae, which enables us to discriminate this species from the other four flea beetle species.

Preliminary flea beetle habitat association models developed from European data have been discussed in scientific forums and submitted for publication.

Once the flea beetle habitat association models are validated then an extension publication 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

Nowierski, R. M., G. J. McDermott, J. E. Bunnell, B. C. FitzGerald, and Z. Zeng. 1996. Isozyme analysis of Aphthona species (Coleoptera: Chrysomelidae) associated with different Euphorbia species (Euphorbiaceae) and environmental types in Europe. Ann. Entomol. Soc. Am. 89: 858-868.

Nowierski, R. M., Z. Zeng, D. Schroeder, and A. Gassmann. 1996. Habitat analyses of Euphorbia species and associated flea beetles in the Aphthona complex from Europe: can we learn something about habitat associations of natural enemies prior to release?, pp. 84-85 In: Programme and Abstracts, IX International Sympos. on Biological Control of Weeds, Stellenbosch, South Africa, January 21-26, 1996, Agricultural Research Council of South Africa.

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.

Zeng, Z., R. M. Nowierski, M. L. Taper, B. Dennis, and W. P. Kemp. 1998. Complex population dynamics in the real world: modeling the influence of time-varying parameters and time lags. Ecology 79: 2193-2209.
Nowierski, R. M., C. B. Huffaker, D. L. Dahlsten, D. K. Letourneau, D. H. Janzen, and G. G. Kennedy. 1999. The influence of insects on plant populations and communities, pp. 585-642. In: C. B. Huffaker and A. P. Gutierrez [Eds.], Ecological Entomology, 2nd ed., John Wiley & Sons, New York.

Question 9: Scientific Publications:

Nowierski, R. M., G. J. McDermott, J. E. Bunnell, B. C. FitzGerald, and Z. Zeng. 1996. Isozyme analysis of Aphthona species (Coleoptera: Chrysomelidae) associated with different Euphorbia species (Euphorbiaceae) and environmental types in Europe. Ann. Entomol. Soc. Am. 89: 858-868.

Nowierski, R. M., C. B. Huffaker, D. L. Dahlsten, D. K. Letourneau, D. H. Janzen, and G. G. Kennedy. 1999. The influence of insects on plant populations and communities, pp. 585-642. In: C. B. Huffaker and A. P. Gutierrez [Eds.], Ecological Entomology, 2nd ed., John Wiley & Sons, New York.

Rees, N. E., R. W. Pemberton, N. R. Spencer, P. C. Quimby, & R. M. Nowierski. 1996. Spurge. In: Rees, N. E., P. C. Quimby, G. L. Piper, C. E. Turner, E. M. Coombs, N. R. Spencer, and L. V. Knutson (Eds.) Biological Control of Weeds in the West. Western Soc. Weed Sci., Bozeman, MT, 31 pp.
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