Progress 07/01/04 to 06/30/07
Outputs
The effects of Aphthona spp., imazapic herbicide, and interseeded native grass species alone or in combination for leafy spurge control were evaluated at two locations in southeastern ND in a 5 yr integrated pest management program. Leafy spurge stem density, canopy cover, and production were reduced for 1 to 2 yr in all treatments that included imazapic, with no difference in control between single and combination treatments. Aphthona spp. and interseeded native grasses alone or combined did not reduce leafy spurge density or cover. Forb and warm-season grass production increased at one location only. Leafy spurge control in areas that have very sandy soils remains problematic. Field experiments were conducted to determine the effect of low temperatures associated with herbicide treatment on Canada thistle control in wheat-potato and potato-wheat sequence with two environments in each crop sequence. Glyphosate and dicamba plus diflufenzopyr were applied to Canada
thistle after harvest regrowth following three temperature regimes of before freeze, after freeze and after two freezes. In the wheat-potato sequence, before freeze and after one freezing temperature increased Canada thistle control 1 yr after treatment compared to after two freezes. Canada thistle was reduced from initial densities by 79% and 71% at the two environments, while densities in the untreated control increased in by as much 78%. Experiments were conducted to determine alfalfa response to tribenuron application rate and timing. Tribenuron caused less than 10% chlorosis of alfalfa when regrowth was 2 cm or shorter but caused at least 36% chlorosis when regrowth was 5 cm or taller. Use of tribenuron in alfalfa that does not reduce forage yield depends on a restricted application period between harvest and 2 cm of alfalfa regrowth. This window of application would only be achievable when forage is harvested fresh for greenchop forage or haylage. The risk of mistiming the
application is significant because yield loss was substantial. The mechanism of resistance to inhibitors of acetolactate synthase (ALS) was investigated in a herbicide-resistant biotype of wild oat. Presence of ALS2 was confirmed in two herbicide-susceptible wild oat lines, and also the A-genome diploids Avena wiestii and Avena strigosa. Surprisingly, these ALS2 genes also had amino acids consistent with resistance at positions 653 and 571. This indicates that ALS2 with sequence typical of herbicide-resistant plants is normally found among Avena spp. and suggests that ALS2 may normally be expressed at a low level in seedlings, but perhaps is expressed at a higher level in herbicide-resistant wild oat. The North Dakota Weed Guide has become the primary source for growers and landowners to access weed control information for invasive species. The results from these studies were made available in both print and electronic format. Over 20,000 copies of the state weed guide were
distributed per year and the number of inquiries to the NDSU weed science web page increased from about 93,000 to 140,000 per year during this study.
Impacts
There was no difference in leafy spurge control between the single treatments of imazapic and combinations of Aphthona spp., imazapic, and interseeded native grasses in a sandy soil environment. Biological control agents and interseeded native grasses take time to establish and increase in population, especially in areas less suitable for establishment, such as sandy soil. Since neither method reliably reduced leafy spurge, cultural methods such as grazing with sheep or goats alone or in combination with herbicides should be implemented to reduce leafy spurge topgrowth and reduce spread of the weed. Research demonstrated the acceptable application timing for tribenuron use in alfalfa to be 0 to 2 cm of regrowth. Since application outside of this range resulted in 40 to 80% yield loss, widespread adoption of tribenuron in alfalfa for Canada thistle control could have been financially devastating. Identification of such a restricted application timing for tribenuron use
in alfalfa prevented loss of forage yield with an estimated value of $24 million annually in North Dakota. Determining the genetics mechanisms of weed resistance to herbicides is important in the development of quick and reliable ways to confirm resistance and predict the likely success of alternative control methods. Herbicide resistance is often associated with mutations that alteration target-site enzymes. However, this research emphasizes that expression of target-site enzymes must also be considered in order to accurately confirm and predict herbicide response using diagnostic tests.
Publications
- Bourcher, R., R. Hansen, R. Lym, A. Norton, D. Olson, C. B. Randall, M. Schwarzlander, L. Skinner. 2006. Biology and biological control of leafy spurge. Forest Health Technology Enterprise Team. USDA Forest Service. 125 pp.
- Christoffers, M. J., V. K. Nandula, K. A. Howatt, and T. R. Wehking. 2006. Target-site resistance to acetolactate synthase inhibitors in wild mustard (Sinapis arvensis). Weed Sci. 54:191-197.
- Christoffers, M. J. and S. N. Pederson. 2006. Acetolactate synthase genes and herbicide resistance in wild oat. Plant and Animal Genome XIV Conference. Abstr. P823.
- Juricek, Chelsea J. 2006. Evaluation of integrated pest management and vegetation impact using Aphthona spp. biological control agents for leafy spurge (Euphorbia esula L.) control. M.S. Thesis, North Dakota State Univ. Fargo. 78 p.
- Lym, R. G. 2007. Leafy spurge control with picloram applied with imazapic or dicamba plus diflufenzopyr. Res. Prog. Rep. West. Soc. Weed Sci. p. 14-15.
- Lym, R. G., and C. G. Messersmith. 2006. Leafy spurge identification and control. North Dakota State Univ. Ext. Ser. Cir. W- 765 revised.
- Ying, J. J. V. Anderson, D. P. Horvath, Y-Q Gu, R. G. Lym, and W. S. Chao. 2006. Subtractive cDNA libraries identify differentially expressed genes in dormant and growing buds of leafy spurge (Euphorbia esula). Plant Mol. Biol. 61:329-344.
- Zhou, J., J. D. Harrington, and C. G. Messersmith. 2007. Information discovery from Canada thistle control research data by using association rule mining. Abstr. Weed Sci. Soc. Am. 47:59.
- Zollinger, R. K., D. M. J. Christoffers, A. G. Dexter, G. J. Endres, T. D. Gregoire, K. A. Howatt, B. M Jenks, R. G. Lym, C. G. Messersmith, A. A. Thostenson, and H. H. Valenti. 2007. 2007 Agricultural Weed Control Guide. North Dakota State Univ. Ext. Ser. Cir. W-253R.
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Progress 10/01/05 to 09/30/06
Outputs
Most research has shown that a late August to late September herbicide application provides effective control of Canada thistle adventitious shoots one year after application. However, crop harvest scheduling conflicts or late maturing crops may delay herbicide applications until after single or repeated frosts. Canada thistle regrowth can influence herbicide efficacy when plants have received a low temperature stress. Growth chamber trials found that a single or repeat freeze of -3 C had little effect on Canada thistle control when glyphosate, dicamba+diflufenzopy, or the combination of glyphosate and dicamba+diflufenzopy herbicides were applied. Herbicides applied in the field prior to late wheat harvest reduced Canada thistle density where application prior to early harvest did not. Canada thistle cover 10 mo after aminopyralid treatment in Theodore Roosevelt National Park was reduced to 6% compared to 31% for the untreated control. Aminopyralid generally did not
affect other plant species in Canada thistle-infested areas such as western snowberry, leafy spurge, Kentucky bluegrass, and western wheatgrass. Cover was unchanged following aminopyralid treatment for most native species including western snowberry, silver sagebrush, western wheatgrass, and needle-and-thread, which averaged about 10% cover each. Tribenuron at 8.4 and 17 g/ha was less injurious to alfalfa with 0 and 2 cm of regrowth after harvest than 5 and 10 cm of regrowth. Tribenuron caused less than 10% chlorosis of alfalfa when regrowth was 2 cm or shorter but caused at least 36% chlorosis and 50% stunting when regrowth was 5 cm or taller. Alfalfa regrowth after harvest did not express symptoms and forage yield of subsequent cuttings was not different than controls. Seedling alfalfa was more susceptible to tribenuron than imazamox in green house trials. Tribenuron at 8.4 g/ha caused at least 19% injury to alfalfa that was in the fourth trifoliolate stage or younger, but imazamox
at 35 g/ha only caused more than 10% injury to unifoliolate alfalfa, 43% injury. Two distinct acetolactate synthase (ALS) genes, ALS1 and ALS2, were previously identified in a wild oat biotype resistant to ALS-inhibiting herbicides. While the DNA sequence of ALS2 was consistent with that of a herbicide-resistant ALS, the same ALS2 gene was also found among susceptible wild oat. Our hypothesis is that ALS2 expression may normally be low in leaf tissue, but perhaps is expressed at a higher level in herbicide-resistant wild oat. Support for the possibility of ALS genes with different expression patterns in some weeds was obtained from wild mustard, where two distinct ALS genes were found to be present in susceptible and resistant plants. However, in wild mustard, sequence consistent with target-site herbicide resistance was only found in herbicide-resistant plants. The ND Weed Guide has become the primary source for growers and landowners to access weed control information for invasive
species and the number of weed guides printed has remained relatively constant at 20,000 copies per year. There were 140,000 inquiries to the NDSU Weed Science Home Page and attached weed id and control information pages.
Impacts
Aminopyralid has a much lower risk profile than other herbicides currently used to control invasive weeds. Aminopyralid has rapidly been adopted by federal land managers for invasive weed control in native areas due in part to our finding of rapid return of native species once Canada thistle was controlled with this herbicide. Research demonstrated the acceptable application timing for tribenuron use in alfalfa to be 0 to 2 cm of regrowth. Since application outside of this range resulted in 40 to 80% yield loss, widespread adoption of tribenuron in alfalfa for Canada thistle control could have been financially devastating. Identification of such a restricted application timing for tribenuron use in alfalfa prevented loss of forage yield with an estimated value of $24 million annually in North Dakota. Herbicide resistance is often associated with target-site alterations. However, this research emphasizes that expression of target-site enzymes must also be considered in
order to accurately confirm and predict herbicide response using diagnostic tests. Field results suggest an increase in Canada thistle control when the plants are treated as late as possible in the fall. This technique is slow to be adopted due to required changes in farming practices.
Publications
- Christoffers, M. J., V. K. Nandula, K. A. Howatt, and T. R. Wehking. 2006. Target-site resistance to acetolactate synthase inhibitors in wild mustard (Sinapis arvensis). Weed Sci. 54:191-197.
- Christoffers, M. J. and S. N. Pederson. 2006. Acetolactate synthase genes and herbicide resistance in wild oat. Plant Animal Genome Conf. Abstract P823.
- Jia, Y., J. V. Anderson, D. P. Horvath, Gu, Y., Lym, R. G., and Chao, W. S. 2006. Subtracted cDNA libraries identify differentially-expressed genes in dormant and growing buds of leafy spurge (Euphorbia esula). Proc. Weed Sci. Soc. Am. 46:30.
- Nissen, S. J., K. G. Beck, P. Westra, R. Lym, R. G. Wilson, L .Wrage, S. Enloe, V. Carrithers, R. A. Masters, and M. Halvstvedt. 2006. Canada thistle control with Milestone. Proc. West. Soc. Weed Sci. 59:63
- Ramsdale, B. K., G. O. Kegode, C. G. Messersmith, J. D. Nalewaja, and C. A. Nord. 2006. Long-term effects of spring wheat-soybean cropping systems on weed populations. Field Crops Res. 97:197-208.
- Samuel, L. W. and R. G. Lym. 2006. Aminopyralid efficacy on Canada thistle and native plant species in Theodore Roosevelt National Park. Proc. West. Soc. Weed Sci. 59:62.
- Zhou, J., B. Tao, E. L. Deckard, and C. G. Messersmith. 2006. Garden huckleberry (Solanum melanocerasium) germination, seed survival, and response to herbicides. Weed Sci. 54:478-483
- Zhou, J., E. L. Deckard, and C. G. Messersmith. 2005. Factors affecting germination of eastern black nightshade (Solanum ptycanthum) seeds. Weed Sci. 53:651-656.
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Progress 10/01/04 to 09/30/05
Outputs
A study was initiated to evaluate Canada thistle control with aminopyralid and effects of Canada thistle and aminopyralid on native rangeland plant communities in Theodore Roosevelt National Park. Research plots were established on native and Canada thistle-infested rangeland of comparable landscape position and vegetation composition with the exception of Canada thistle. Initial evaluations found an increase in native species following aminopyralid application in Canada thistle infested areas of the park. Aminopyralid greatly reduced Canada thistle and some native broadleaf plants, but not native grasses. Experiments were conducted to evaluate alfalfa response to tribenuron application rate and timing when used to control invasive weeds. Tribenuron applied at 4.2 and 68 g ai per ha to 5 cm tall alfalfa caused severe chlorosis and stunting. Tribenuron at 68 g per ha caused 56% stunting and 42% chlorosis but did not kill plants. Alfalfa regrowth after harvest did not
show injury and forage yield of subsequent cuttings was not different than controls. Two distinct acetolactate synthase (ALS) genes, ALS1 and ALS2, were identified in a wild oat biotype resistant to ALS-inhibiting herbicides. While ALS1 had wild-type sequence, ALS2 inferred alanine at amino acid position 571 instead of wild-type valine, and asparagine at amino acid position 653 instead of wild-type serine. These mutations were consistent with herbicide resistance. However, we also found ALS2 inferring alanine 571 and asparagine 673 in two herbicide-susceptible wild oat accessions, and also in diploid Avena wiestii carrying the A genome. This indicates that ALS2 with sequence typical of herbicide-resistant plants is normally found among Avena spp. Our hypothesis is that ALS2 expression may normally be low in leaf tissue, but perhaps is expressed at a higher level in herbicide-resistant wild oat. ALS enzyme from susceptible and suspected-resistant lines of crambe has been assayed in
laboratory experiments to determine inhibition of enzyme activity with imazamox. Preliminary interpretation of data is that the ALS enzyme from both of the lines has similar sensitivity to imazamox. In addition, a whole-plant dose response study failed to separate susceptible from three suspected-resistant crambe lines. Initial evaluation of Canada thistle overwintering found little correlation between the actual sub freezing soil temperature subsequent plant regrowth. Perhaps length of freezing temperature is more important than the absolute minimum temperature for Canada thistle winter hardiness.
Impacts
Aminopyralid is a new low rate herbicide used to control invasive weeds such as Canada thistle and the knapweed complex. Aminopyralid has a much lower risk profile than other herbicides currently used to control invasive weeds and is likely to be widely used by federal land managers. Initial results indicate a rapid return of native species once Canada thistle was controlled with aminopyralid. Herbicide resistance is often associated with target-site alterations. However, this research emphasizes that expression of resistant enzymes must also be considered in order to accurately confirm and predict herbicide response using diagnostic tests. Developing management strategies to reduce Canada thistle in crops such as spring wheat and dry beans is essential for potato production, especially since field results suggest that potato harvest operations increase the Canada thistle population the following year and greatly reduce efficacy with post emergence herbicides.
Likewise, understanding the influence of freezing temperatures before and shortly after a post emergence herbicide will help land managers apply herbicides at an optimal time to kill Canada thistle roots.
Publications
- Christoffers, M. J., L. W. Mengistu, and S. N. Pederson. 2005. Analysis of acetolactate synthase gene sequences from flucarbazone-resistant wild oat (Avena fatua). Abstr. Weed Sci. Soc. Am. 45:69.
- Dahl, L. M., K. A. Howatt, and D. W. Meyer. 2004. Alfalfa response to tribenuron. North Central Weed Sci. Soc. Abstr. 59:023.pdf. North Central Weed Sci. Soc., Champaign, IL. (Dec. 2004 CD).
- Lym, R. G. and K. J. Deibert. 2005. Diflufenzopyr influence on leafy spurge (Euphorbia esula) and Canada thistle (Cirsium arvense) control varies by herbicide. Weed Technol. 19:329-341.
- Tao, B., J. Zhou, C. G. Messersmith, and J. D. Nalewaja. 2005. Interaction of bentazon and glyphosate for canola and wheat. Weed Sci. Soc. Amer. Abstr. 43 [CD-ROM computer file]. Weed Sci. Soc. Amer. Abstr. 45:12.
- Zhou, J., C. G. Messersmith, and J. Davidson-Harrington. 2005. Weed-Miner: A system prototype within WeedIT for mining a weed research database. Weed Sci. Soc. Amer. Abstr. 135 [CD-ROM computer file]. Weed Sci. Soc. Amer. Abstr. 45:40-41.
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Progress 10/01/03 to 09/30/04
Outputs
The purpose of this research is to address 1) factors affecting long-term integrated management of leafy spurge; 2) the effects of Canada thistle growth stage and cold temperature on control in crops; 3) the effect of Canada thistle control on alfalfa forage production, quality, and hardiness; 4) the emergence periodicity of weeds in crop including Canada thistle; 5) ALS over-expression as a possible mechanism of herbicide resistance; and 6) distribution of the results and conclusions of this research to farmers and land managers in a variety of extension media formats including computer-based systems. Research will be conducted in a variety of environments ranging from leafy spurge in pasture and wildlands, to Canada thistle in cropland and greenhouses, to genetic marker work conducted under laboratory conditions. The long-term goal is to develop integrated management systems for established invasive weeds and to identify and contain newly emerging invasive weed
species. A variety of techniques will be used to accomplish these goals including chemical, biological, mechanical, and cultural control methods.
Impacts
None to date.
Publications
- No publications reported this period
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