Ten herbicide treatments were evaluated for early season control of three broadleaf weeds and effects on marketable potato yields in low-organic, coarse-textured soil. All treatments controlled prostrate pigweed 100%. Trifluralin with metolachlor or with EPTC did not control kochia well. Pendimethalin alone or with EPTC controlled Russian thistle poorly, and produced the lowest marketable tuber yields. Fluorochloridone at 0.6 kg ai/ha caused chlorosis and reduced potato yield 11%. Treatments with metribuzin tended to have high potato yields.

Leafy spurge control with four herbicides was evaluated at nine sites in six Great Plains states. Sulfometuron alone did not control leafy spurge satisfactorily 12 mo after treatment (MAT). Sulfometuron plus dicamba at 105 plus 2240 g ai ha−1, when spring- or fall-applied, averaged 26 and 89% control and 31 and 86% grass injury, respectively, 12 MAT. Sulfometuron plus picloram at 105 plus 560 g ai ha−1, when spring- or fall-applied, averaged 63 and 92% control and 19 and 89% grass injury, respectively, 12 MAT.

The potential for future commercialization of glyphosate-resistant wheat necessitates evaluation of agronomic merits of this technology. Experiments were established to evaluate glyphosate-resistant wheat and weed responses to glyphosate rate, application timing, and tank mixtures. Glyphosate at 1,680 g/ha did not injure wheat. Wheat response to glyphosate applied to one- to three- or three- to five-leaf wheat was not different from that of untreated wheat. Wheat was injured more from glyphosate plus thifensulfuron or glyphosate plus dicamba than from individual herbicides at one of six locations, but grain yield was not affected by glyphosate tank mixtures. Glyphosate application timing did not affect control of wild oat or common lambsquarters 56 d after treatment. Glyphosate when applied to one- to three-leaf wheat provided better control of wild buckwheat than later glyphosate application, whereas glyphosate applied to three- to five-leaf wheat provided the best control of green and yellow foxtail, redroot pigweed, and Canada thistle. Weed control with glyphosate tended to be better than with conventional herbicides, and wheat treated with glyphosate produced approximately 10% more grain than wheat treated with conventional herbicide tank mixes.

Laboratory, greenhouse, and field experiments were conducted at the Lacombe Research Station to determine if CCC, ethephon, or CCC/ethephon had direct activity on quackgrass rhizome buds, and to determine if foliar applications of CCC/ethephon could predispose quackgrass to more effective control with sethoxydim. CCC, ethephon, and CCC/ethephon had growth regulating effects on the axillary buds and the apex of detached quackgrass rhizomes. CCC increased rhizome bud sprouting on rhizomes with the apex excised, but not on rhizomes with an intact apex. Ethephon or CCC/ethephon inhibited bud sprouting on rhizomes with an intact or excised apex. CCC/ethephon, but not CCC or ethephon alone, increased rhizome elongation on rhizomes with intact apices. In the greenhouse, pretreatments of CCC/ethephon increased sethoxydim activity on quackgrass rhizome buds and caused lower shoot emergence from one-bud rhizome segments. Results of field experiments were less consistent than those in the greenhouse. However, sometimes CCC or CCC/ethephon pretreatments resulted in increased quackgrass control in the field with sethoxydim.

Field studies were conducted in 1994 and 1995 to evaluate CGA-152005 for weed control and effect on peanut (Arachis hypogaea) yield in Texas peanut production areas. CGA-152005 at 10 to 20 g/ha controlled eclipta (Eclipta prostrata), golden crownbeard (Verbesina enceliodes), and Palmer amaranth (Amaranthus palmeri) > 90% when applied preemergence (PRE) or soon after peanut emergence (EPOST). CGA-152005 postemergence (POST) controlled eclipta > 95%; sandhills amaranth (Amaranthus arenicola) 99%; golden crownbeard, pitted morningglory (Ipomoea lacunosa), and hophornbeam copperleaf (Acalypha ostryifolia) < 80%; and Palmer amaranth and ivyleaf morningglory (Ipomoea hederacea) from 37 to 89%. CGA-152005 injured peanut up to 37% and reduced yield up to 94%.

Peanuts are not often used as a true oilseed crop, especially for the production of fuel. However, peanut could be a feedstock for biodiesel, especially in on-farm or small cooperative businesses, where producers can dictate the cost of making their own fuel. Field studies were conducted in 2005 and 2006 to assess low-cost weed-control systems for peanuts that would facilitate the economic viability of peanut biodiesel. Four preselected herbicide costs ranging from $25 to $62/ha and two application timings were compared with nontreated ($0/ha) and typical ($115/ha) herbicide programs for weed control and peanut oil yield. A peanut oil yield goal of 930 L/ha was exceeded with multiple low-cost herbicide systems in 3 of 4 site–yr. The main effect of application timing was only significant for a single site–year in which oil yield increased linearly with cost of the PRE and POST weed-control system. An herbicide cost of $50/ha, using PRE and POST applications, was consistently among the highest in oil yield, regardless of site–year, exceeding the typical (high value) programs in 3 of 4 site–yr. Use of reduced rates of imazapic (0.5× or 0.035 kg ai/ha) was detrimental in 2 of 4 site–yr. Weed control, and thus oil yields, were most dependent on species present at each location and not on input price. Data from this series of studies will allow researchers and entrepreneurs to more accurately assess the viability and sustainability of peanut biodiesel.

A seedling bioassay was used to determine the response of triallate-resistant (R) and -susceptible (S) wild oat populations to difenzoquat and EPTC. The bioassay, based on seedling shoot length at 10 d after treatment, provided a reliable and rapid means of determining if wild oat populations were resistant to difenzoquat. Using a bioassay concentration of 15 ppm difenzoquat, it was possible to identify populations that were resistant to the recommended foliar-applied rate (0.85 kg ai/ha). Expected herbicide dosages that reduced shoot length by 50% (ED50) derived from nonlinear regression analysis indicated three and two levels of response to difenzoquat among eight S and seven R populations, respectively, indicating within population variability in their response to difenzoquat. Of the populations tested, none was resistant to EPTC. On the contrary, some R populations had lower ED50 values than did S populations, suggesting an increased sensitivity to EPTC.

Herbicides are an important tool for managing weeds where prescribed fire is used for rangeland improvement. Understanding how the season of herbicide application relates to prescribed burning is important. Our objective was to determine the effect of picloram and chlorsulfuron on Dalmatian toadflax cover, density, and biomass, where these herbicides were applied in the fall before burning or in the spring before or after burning. Six herbicide treatments and an untreated check were applied in a randomized complete block design with four replications to a prescribed burn at two sites infested with Dalmatian toadflax in Montana, United States. Herbicides were applied in the fall preburn, spring preburn, and spring postburn. Site 1 was treated in 1999 and 2000, and site 2 was treated in 2000 and 2001. Cover, biomass, and density of Dalmatian toadflax were sampled in September 2000, 2001, and 2002 at site 1 and September 2001 and 2002 at site 2. At site 1, cover, biomass, and density of Dalmatian toadflax were at least 76% lower compared with the check in both spring-applied picloram treatments, whereas the fall picloram treatment had similar Dalmatian toadflax cover, biomass, and density compared with the check 3 yr after application. By 2002, chlorsulfuron reduced Dalmatian toadflax cover, biomass, and density by at least 79% compared with the check in all timings of application at site 1. At site 2, Dalmatian toadflax cover, biomass, and density were reduced by at least 86% for all picloram and chlorsulfuron treatments in 2002, 2 yr after application. Chlorsulfuron applied in the fall or the spring and picloram applied in the spring effectively suppressed Dalmatian toadflax cover, biomass, and density for up to 3 yr.

Observations in a citrus grove indicated that hairy beggarticks numbers were higher in plots receiving thiazopyr alone or thiazopyr with oxyfluorfen than in nontreated plots. At 120 days after treatment (DAT), approximately 90% more hairy beggarticks plants had emerged in plots receiving thiazopyr at 0.56 kg ai/ha than in nontreated plots. A tank mix of thiazopyr plus oxyfluorfen, each at 0.56 kg/ha, resulted in a 55% increase in hairy beggarticks number at 120 DAT. Greenhouse studies using seeds collected from sites with or without herbicide history produced similar results. Oxyfluorfen at 0.28 kg/ha stimulated seed germination but injured seedlings by 47% or more at 36 DAT when applied at higher rates. Thiazopyr applied at 0.56 kg/ha antagonized the preemergence activity of oxyfluorfen at 0.28 or 0.56 kg/ha. Thiazopyr at 1.12 kg/ha stimulated hairy beggarticks germination by 37% compared with nontreated containers.

Path rush can become problematic on golf course fairways, especially on roughs where continuous golf cart or maintenance equipment traffic occurs. Research trials conducted in 2003 and 2004 compared the efficacy of 2,4-D and mixtures containing 2,4-D in single or sequential applications to herbicides without 2,4-D for path rush control in bermudagrass roughs. Sequential applications of 1.1 kg ae/ha 2,4-D or 0.8 + 0.2 + 0.1 kg ae/ha 2,4-D + MCPP + dicamba provided 95% path rush control with no injury to bermudagrass, 15 wk after initial treatment (WAIT). Single applications of 1.1 + 0.3 + 0.1 kg/ha 2,4-D + MCPP + dicamba or 1.1 kg/ha 2,4-D provided at least 81% path rush control, 15 WAIT. Treatments without 2,4-D did not provide acceptable levels of control (34% or less, 15 WAIT). 2,4-D applied alone or in preformulated mixtures provided excellent path rush control compared to treatments without 2,4-D. Sequential applications of these treatments provided greater path rush control than single applications. However, only the sequential application of 0.8 + 0.2 + 0.1 kg/ha 2,4-D + MCPP + dicamba provided greater path rush control than the single application. Results from these studies suggest that 2,4-D is a key herbicide for path rush control.

Guar production in the United States is limited to a relatively small region in the semiarid southern Great Plains of Texas and Oklahoma. The lack of POST broadleaf herbicides is a potential limiting factor to increased production. A greenhouse study was initiated in 2001 at the Texas A&M Research Center near Vernon, TX to evaluate guar tolerance to 10 POST herbicides typically used in soybean or cotton. Guar seedlings were grown in pots, and herbicides with appropriate adjuvants were applied to 3-wk-old seedlings at the registered rate (1×) and twice (2×) the registered rate for soybean or cotton. The study was repeated twice, with six replications in each run. Twenty-eight d after treatment (DAT), visual injury and aboveground dry weight of viable biomass were recorded for each plant. Significant differences (P = 0.05) were noted among herbicides for visual injury and viable biomass. Little or no differences in visual injury and aboveground dry weight were observed between the control (no herbicide applied) and the 1× rate of 4-(2,4-dichlorophenoxy)butanoic acid, bentazon, or imazethapyr 28 DAT. A 1× application rate of acifluorfen, imazamox, thifensulfuron, or bromoxynil caused minor visual injury of 7 to 9% and a reduction in dry weight of 8 to 23%. Pyrithiobac and chlorimuron caused 38 and 47% visible injury and a 35 and 58% reduction in dry weight, respectively. Guar was most sensitive to lactofen, with the 1× rate causing 100% visual injury and no recoverable aboveground biomass. This greenhouse study identified three POST herbicide candidates with potential to control broadleaf weeds in guar without noticeable plant injury, and offers data to support herbicide registrations for this minor crop.

Field and greenhouse studies were conducted from 1996 to 2000 to determine tropical soda apple fruit size required for mature seed, overwintering survival potential of seeds, and growth and fruit production in a containment area near Stoneville, MS (latitude 33°25′N). Seedling emergence was ≥ 50% from tropical soda apple fruit > 1.8 cm in diameter. Tropical soda apple overwintering emergence was 14, 10, 48, 42, and 13% from seed alone and 86, 83, 48, 41, and 18% for seeds in tropical soda apple fruit overwintering at 100, 0, −5, −10, and −15 cm from the soil surface, respectively. Before frost (early November), average tropical soda apple plant heights were 0.8, 0.6, and 0.7 m; plant diameters were 2.6, 1.7, and 2 m; fruit produced per tropical soda apple plant were 415, 342, 128; and plant weights were 9.9, 9.5, and 4.9 kg at 27 wk after transplanting (WATP) for 1996, 1997, and 1998, respectively. Regeneration from overwintering tropical soda apple roots varied depending on the winter conditions. These results suggest that tropical soda apple plants can survive mild winters.

The response of ‘Florico,’ ‘Victoria,’ and 'Stan II’ triticale to 2,4-D, dicamba, 2,4-D plus dicamba, diclofop, and thifensulfuron plus tribenuron applied POST during the tillering stage was examined. At rates twice those recommended for application to wheat, Victoria and Stan II were not injured, and injury to Florico was less than 10%. None of the herbicides or combinations adversely affected plant height at maturity, tiller or spike production, grain weight/spike, kernel weight, kernels/spike, yield, or test weight of any cultivar. Cultivars varied in tiller production, height, yield, test weight, kernel weight, and kernels/spike.

Bird vetch is a perennial Eurasian plant which, unlike many exotic weed species, can invade low fertility areas that have not been disturbed. It also is common in pastures, woodland, and tall forb communities. Bird vetch is expanding along Alaskan roadsides, in urbanized areas, and in low density forests. A greenhouse study was conducted to determine efficacy of six herbicide treatments applied at reduced rates in 2005 and again in 2006 for bird vetch seedling control. Bird vetch seedlings were tolerant of reduced rates of chlorsulfuron and 2,4-DB; however, complete control was achieved with rates of clopyralid, dicamba plus diflufenzopyr, triclopyr, and 2,4-D that were a fourth to an eighth of the full registered rate. These results will be important for developing effective, low-cost methods for controlling bird vetch in Alaska, especially on the outer margins of infestations.

A 2-yr field study was conducted to evaluate the efficacy of ICIA-0051 for the control of annual grass and broadleaf weed species in conventional tillage corn. Treatments consisted of postemergence applications of ICIA-0051 alone and in combination with cyanazine or atrazine. ICIA-0051 at 0.6 kg ha-1 alone and in combination with cyanazine or atrazine at 1.1 kg ha-1 controlled large crabgrass, yellow foxtail, fall panicum, common lambsquarters, and redroot pigweed effectively (over 90%). The addition of cyanazine or atrazine at 1.1 kg ha-1 to the lowest rate (0.3 kg ha-1) of ICIA-0051 also improved large crabgrass, yellow foxtail, and fall panicum control by 9, 7, and 26%, respectively. None of the treatments of ICIA-0051 except the highest rate (1.1 kg ha-1) reduced either silage or grain yields of corn.

The conflicts over management of natural resources, especially on public lands, have resulted in a high level of frustration among many of the interested parties. There are many underlying causes of the conflicts, but I think several major societal trends must be considered. During the past several decades, there has been increased emphasis on participatory democracy, with the public seeking more involvement in decision making and policy formulation. A related trend is the decline in the public image of science and lack of trust in state and federal agencies. Individual members of society desire to be included in decision making, and may not necessarily view scientists as capable of providing the answers to natural resource issues. One response to natural resource conflicts is to form a group of interested individuals from diverse backgrounds to develop solutions. These groups may also work toward policy development. Coalitions or working groups may take many forms. There are two basic types of groups I will mention: 1) those formed to address a specific issue over a set time period, and 2) those formed to foster communication, interaction, and education. Many working groups have been formed over controversies, but effective use of the groups might also keep controversies from arising. In my opinion, scientists should be active participants in natural resource working groups. Participation provides the opportunity to incorporate science in decision-making and may also guide research efforts insuring that the results are of value to a wider cross-section of society.

‘Russet Burbank’ potato tolerance to dimethenamid-p applied preemergence at 0.7, 1.4, or 2.9 kg ai/ha was assessed in field studies conducted at Aberdeen, ID and Ontario, OR. Although crop injury was evident approximately 2 wk after treatment, most injury had diminished by row closure 2- to 3-wk later. Initial injury did not translate to yield loss and U.S. No. 1 and total tuber yields in dimethenamid-p–treated plots were similar to yields in the untreated, weed-free control.

Field trials were conducted in 2004 and 2005 to identify sulfonylurea (SU) herbicides that would provide improved weed control, minimal soil residual, and crop safety to SU-resistant chicory. SU-resistant chicory had previously been selected in vitro for resistance to chlorsulfuron. Our research evaluated three commercial, nonresistant and three breeding lines of SU-resistant chicory. Each of the cultivars was treated POST at the two true-leaf growth stage with either foramsulfuron, rimsulfuron, rimsulfuron plus thifensulfuron, tribenuron, thifensulfuron, thifensulfuron plus tribenuron, triflusulfuron, flumetsulam, or imazamox at normal use rates. Established plant densities and root yields of SU-resistant chicory breeding lines were greater than or equal to the densities and root yields of commercial cultivars. The plant density of commercial chicory cultivars was reduced by rimsulfuron, rimsulfuron plus thifensulfuron, tribenuron, and thifensulfuron plus tribenuron, but SU-herbicides did not reduce the density of SU-resistant breeding lines. SU-resistant chicory differed in cross-resistance to SU-herbicides, with tribenuron causing the most crop injury and thifensulfuron, the least. Weed control varied between the SU-herbicides. The greatest reduction in weed biomass occurred with tribenuron, thifensulfuron plus tribenuron, and rimsulfuron plus thifensulfuron; the least reduction occurred with triflusulfuron, foramsulfuron, and rimsulfuron. Chicory root yields comparable to the hand-weeded treatment were achieved with rimsulfuron plus thifensulfuron and thifensulfuron plus tribenuron treatments. The SU herbicides that met the initial project objectives of crop tolerance and improved weed control were combinations of rimsulfuron plus thifensulfuron and thifensulfuron plus tribenuron.

In five field experiments from 1986 to 1988, herbicides were evaluated alone and in combinations for weed control in water-seeded rice. Combinations of bensulfuron with either molinate or thiobencarb applied into the paddy water at the 2-leaf stage of rice, controlled all broadleaf and sedge weeds, and 92% or more early watergrass. These combinations were equivalent to a commercial standard of molinate at the 2-leaf stage followed by a separate application of bentazon to the drained paddy at midtillering.