| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00222 | |
| Title | *Biological Control in Pest Management Systems of Plants |
| Investigator(s) | Hufbauer, RA; |
| Department | Bioagricultural Sciences and Pest Mgmt. |
| Objectives | 3. (Goal A) Determine systematics and biogeography of pests and natural enemies. 6. (Goal A) Evaluate natural enemy efficacy and study ecological/physiological basis for interactions. |
| Approach | Objective 3. I am exploring the genetic population structure of two invasive weeds (diffuse and spotted knapweed) using molecular markers. We are using both molecular markers and cytological techniques. We are determining the frequency and importance of hybridization in the weed invasion, and attempting to determine the Eurasian origins of the weeds. Objective 6. We are exploring the ecological and physiological basis for host-plant preference in a biological control agent of dalmatian and yellow toadflax (Linaria dalmatica and L. vulgaris) using behavioral choice tests, and physiological no-choice tests. |
| Keywords | Centaurea maculosa, Centaurea stoebe, Linaria vulgaris, Linaria dalmatica, biological control, population genetics, noxious weeds |
| Progress Reports | |
| 2003 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. Two issues of overriding importance in biological control are safety and efficacy. In our program we are addressing both. The main weeds we are working with are Dalmatian and yellow toadflax, diffuse and spotted knapweed, and garlic mustard. With the toadflaxes, we have documented that one of the most common biological control agents has a strong preference for yellow toadflax, and so is not effective on Dalmatian toadflax. With diffuse and spotted knapweed, we have found populations in the native range that are closely related to invasive populations. Those populations will be searched for new potential biological control agents. We have also found that hybrids of diffuse and spotted may not pose as much of an increased risk to invasion as feared, given their low production of allelochemicals. For garlic mustard, we have developed a method to distinguish morphologically identical larvae of different candidate biological control agents with molecular techniques, and have planned experiments with those larvae to estimate the heritability of a key trait: oviposition preference. Because the rate of adaptive evolution is directly proportional to heritability, quantifying heritabilities enables us to begin estimating the risk of evolution of host range. |
| 2004 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. Two issues of overriding importance in biological control are safety and efficacy. In our program we are addressing both. The main weeds we are working with are Dalmatian and yellow toadflax, diffuse and spotted knapweed, and garlic mustard. With the toadflaxes, we have documented that one of the most common biological control agents has a strong preference for yellow toadflax, and so is not effective on Dalmatian toadflax. It also performs better on yellow toadflax than Dalmatian. The combination of differences in preference and performance on the two hosts helps explain the low population sizes of this beetle on Dalmatian toadflax. With the knapweeds, we are focusing on discovering where in the native range the invasive populations originated, and how hybridization influences interactions with insects. A key finding from the knapweed work is that a cryptic species that looks like spotted knapweed appears to be present in North America. In addition, we have improved upon methods for studying allelopathy in this system and discovered that the putative allelochemical from spotted knapweed can disappear from soil within 24 hours, and have found that carbon (often used to adsorb allelochemicals) can alone increase plant growth. For garlic mustard, we are focusing on interactions between it and potential biological control agents. We have found significant genetic structuring of populations of the potential biological control agents in the native range using neutral loci. Pending external funding, the host ranges of these distinct populations will be evaluated to determine the risk of host-range evolution following release. Another component of our research is understanding the genetic consequences of biological control introductions. We have found that introductions can reduce variation at neutral loci in two systems, a parasitoid used in biological control of aphids, and a gall-forming midge used in biological control of the weed leafy spurge. The ecological significance of these changes at the molecular level remains to be explored. |
| 2005 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. Two issues of overriding importance in biological control are safety and efficacy. In our program we are addressing both. The main weeds we are working with are Dalmatian and yellow toadflax, diffuse and spotted knapweed, and garlic mustard. With the toadflaxes, we have documented that one of the most common biological control agent has a strong preference for yellow toadflax, and so is not effective on Dalmatian toadflax. It also performs better on yellow toadflax than Dalmatian. The combination of differences in preference and performance on the two hosts help explain the low population sizes of this beetle on Dalmatian toadflax. With the knapweeds, we are focusing on discovering where in the native range the invasive populations originated, and how hybridization influences interactions with insects. A key finding from the knapweed work is that a cryptic species that looks like spotted knapweed appears to be present in North America. In addition, we have improved upon methods for studying allelopathy in this system and discovered that the putative allelochemical from spotted knapweed can disappear from soil within 24 hours, and have found that carbon (often used to adsorb allelochemicals) can alone increase plant growth. For garlic mustard, we are focusing on interactions between it and potential biological control agents. We have found significant genetic structuring of populations of the potential biological control agents in the native range using neutral loci. Pending external funding, the host ranges of these distinct populations will be evaluated to determine the risk of host-range evolution following release. Another component of our research is understanding the genetic consequences of biological control introductions. We have found that introductions can reduce variation at neutral loci in two systems, a parasitoid used in biological control of aphids, and a gall-forming midge used in biological control of the weed leafy spurge. The ecological significance of these changes at the molecular level remains to be explored. |
| 2006 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. Two issues of overriding importance in biological control are safety and efficacy. In our program we are addressing both. The main weeds we are working with are Dalmatian and yellow toadflax, diffuse and spotted knapweed, and garlic mustard. One of our key findings from this year relates to hybrids between diffuse and spotted knapweed. First, work on ploidy levels of the plants reveals that diffuse knapweed is diploid while spotted knapweed is tetraploid. This means that on-going hybridization is unlikely to be occurring, and that the hybrids in the U .S. were introduced from Europe. Second, the hybrids in the U.S. had higher levels of damage from herbivores than diffuse knapweed. In combination, these findings suggest that hybrids might not be the 'superweed' they were feared to be. |
| Impact | |
| 2003 | The information on the beetle preference in the toadflax system will alter redistribution programs to be more effective, and will be used to minimize the sale by biological control companies of ineffective agents to unsuspecting customers. Information from the Centaurea system is being used by USDA ARS colleagues to target their search for more effective biological control agents. Our findings on the alleopathic output of the hybrids suggests that they need not be focused on to the exclusion of other infestations for control. Findings that California populations of spotted knapweed are distinct will be used to target those populations for additional control efforts. Our technique to identify larval individuals of the candidate biological control agents for garlic mustard will be used to facilitate accurate testing of host specificity, and should therefore result in safer biological control. |
| 2004 | The information on the beetle preference and performance in the toadflax system is being incorporated in to a Forest Service manual on management of yellow and Dalmatian toadflax. This should minimize time and money used in attempts to establish populations of the beetle on Dalmatian toadflax. Information from the Centaurea system has led to efforts to eradicate what appears to be a distinct species. Scientifically, the methodology developed for working with the putative allelochemicals, and the finding that carbon alone can facilitate plant growth should facilitate future work on allelopathy. Preliminary population genetic work on the garlic mustard weevils will be used in the materials provided tot he technical advisory group (TAG) that evaluates the risks and benefits of new biological control introductions, and makes recommendations to USDA APHIS PPQ officials regarding new releases. Information on the genetic consequences of biological control introductions likely will influence the way that releases are done, to minimize the loss of genetic variation. |
| 2005 | The information on the beetle preference and performance in the toadflax system has been incorporated in to a Forest Service manual on management of yellow and Dalmatian toadflax. This should minimize time and money used in attempts to establish populations of the beetle on Dalmatian toadflax. Information from the Centaurea system has led to efforts to eradicate what appears to be a distinct species. Scientifically, the methodology developed for working with the putative allelochemicals, and the finding that carbon alone can facilitate plant growth should facilitate future work on allelopathy. Preliminary population genetic work on the garlic mustard weevils will be used in the materials provided tot he technical advisory group (TAG) that evaluates the risks and benefits of new biological control introductions, and makes recommendations to USDA APHIS PPQ officials regarding new releases. Information on the genetic consequences of biological control introductions likely will influence the way that releases are done, to minimize the loss of genetic variation. |
| 2006 | Managers have been quite concerned about hybrids they have observed in the field. Our results suggest that the hybrids might not be any more of a problem than the parental species, and may even be less problematic given that they experience higher rates of herbivory. |
| Publications | |
| 2003 |
Hufbauer, RA, RA Marrs, AK Jackson, R Sforza, HP Bais, JM Vivanco and SE Carney. 2004 Population structure, ploidy levels and allelopathy of spotted and diffuse knapweed in North America and Eurasia. Proceedings of the XI International Symposium on Biological Control of Weeds, JM Cullen, Editor. Commonwealth Scientific and Industrial Research Organization (CSIRO) , Melbourne, Australia. |
| 2004 |
Hufbauer, RA, Bogdanowicz,SM, and Harrison,RG. 2004. The population genetics of a biological control introduction: microsatellite and mtDNA variation in native and introduced populations of Aphidius ervi, a parasitoid wasp. Molecular Ecology. 13:337-348. Hufbauer, RA, Marrs,RA, Jackson,AK, Sforza,R, Bais,HP, Vivanco,JM and Carney, SE. 2004. Population structure, ploidy levels and allelopathy of spotted and diffuse knapweed Pp. 121-126 in North America and Eurasia. Proceedings of the XI International Symposium on Biological Control of Weeds, Cullen,JM, Briese,DT, Kriticos,DJ, Lonsdale,WM, Morin,L, Scott,JK eds. CSIRO Entomology, Canberra, Australia. Lloyd, CJ, Norton,AP, Hufbauer,RA, and Bogdanowicz,SM. 2004. Microsatellites isolated from the gall midge Spurgia capitigena (Diptera: Cecidomyiidae), a biological control agent of leafy spurge. Molecular Ecology Notes 4: 605-607. McClay, AS, Crisp,MD, Evans,HC, Heard,T., Hufbauer,RA, Qin,T-K and Shaw,R. 2004. Centres of origin: do they exist, can we identify them, does it matter? Pp. 619-620 in Proceedings of the XI International Symposium on Biological Control of Weeds, Cullen,JM, Briese,DT, Kriticos,DJ, Lonsdale,WM, Morin,L, Scott,JK eds. CSIRO Entomology, Canberra, Australia. |
| 2005 |
Blair, A.C., Hanson, B.G., Brunk, G.R., Marrs, R.A., Westra, P., Nissen, S.J., and Hufbauer, RA. 2005. New techniques and findings in the study of a candidate allelochemical implicated in invasion success. Ecology Letters. 8: 1039-1047. Hufbauer, R.A. and Roderick, G.K. 2005. Microevolution in biological control: mechanisms, patterns and processes. Biological Control. 35:227-239. Lloyd, C.J., Hufbauer, R.A., Jackson, A.K., Nissen, S.J., and Norton, A.P. 2005. Pre- and post-introduction patterns in neutral genetic diversity in the leafy spurge gall midge. Biological Control 33:153-164. MacKinnon, D.K., Hufbauer, R.A., and Norton, A.P. 2005. Host-plant preference of an inadvertently introduced biological control agent. Entomologia Experimentalis et Applicata. 116:183-189. Wilson, L.M., Sing, S., Piper, G., DeClerck-Floate, R., Hansen, R., MacKinnon, D.K. and Randall, C. 2006. Biology and biological control of toadflax. USFS, FHTET-xx06. |
| 2006 |
Blair AC, SJ Nissen, GR Brunk, RA Hufbauer. 2006. Lack of evidence for an ecological role of the putative allelochemical (+/-)-catechin in spotted knapweed invasion success. Journal of Chemical Ecology. 32:2327-2331. Marrs, RA, RA Hufbauer, SM Bogdanowicz, R Sforza. 2006. Nine polymorphic microsatellite markers in Centaurea stoebe L. [subspecies C. s. stoebe and C. s. micranthos (S. G. Gmelin ex Gugler) Hayek] and C. diffusa Lam (Asteraceae). Molecular Ecology Notes. 6:897-899. |