Brief Summary of Minutes of Annual Meeting

Minutes: 2014 Meeting A series of online meetings were held in 2014 using Adobe Connect. The following primarily summarizes the final Adobe Connect meeting, which was held to discuss the 2015 meeting and select a new Chair. Election of Chair for 2014-15 – Karen Renner agreed to serve as Chair for the next year. 2015 meeting information: the meeting will coincide with the 2015 Weed Science Society of America (WSSA) annual national conference in Lexington, KY. Suggestions for the meeting are as follows: 1. Start in the morning on the day WSSA starts (Monday) and conclude approximately 2 hours after lunch. Karen Renner will chair the meeting and Erin Hill will take notes. 2. Determine the need for a conference call to accompany the in-person meeting once attendance at WSSA is known. 3. Have everyone bring a list of presentations/abstracts and a separate list of publications from 2011 (beginning in October) through 2015. 4. Assign individuals to summarize Objectives 1 and 2 for the meeting. Gallandt and Curran summarize Objective 1. VanGessel and Renner summarize Objective 2 to date. Mohler report on their research from Obj. 2 for 2014. 5. Discuss Objective 3 data: Michigan, Cornell, others. Discuss what to do with the research data. Assign individual(s) to be lead author on the paper. 6. Discuss the direction of future research by this group. This work terminates September 2016 but we will have our objectives completed one year early. We can have the report written and hold until presentations/publications are completed in late 2015 and 2016 and then submit. 7. Consider asking the NC-1191 chairperson and secretary to the meeting to discuss the direction of that group which is on the same timeline for a proposal termination and new pre-proposal that we are. They may be meeting at WSSA (however they often meet in the summer). Their title is “Weeds as Phytometers in Changing Environments” (previously this group was NC-1026 Weed Population Dynamics for long term decision making… (or something like that). OTHER NOTES: Objective 1 (effect of soil conditions and cultivation implements on weed control): Two states participated in this objective: Maine and Pennsylvania. Since only two states participated and followed different protocols, this objective was not discussed during our meetings. The researchers involved in Objective 2 (the effect of termination of seed production/viability) agreed to share results to present a poster at the 2015 WSSA meeting. Mark VanGessel agreed to lead this effort. The Michigan and Delaware research teams used similar methods and species and will work together to develop a paper. Michigan (Karen and Erin) will take the lead in developing that paper. The Cornell and U. Maine teams u used different species and are at different stages in their work so they will decide on how they want to proceed with field research and in developing an additional paper or papers. Objective 3 (effect of soil amendments on seed mortality). Research is ongoing and will be discussed during the 2015 meeting. Methods vary among the research teams so a conversation should occur to clarify if a group paper will be developed. There was a suggestion to focus the pre-proposal on the Northeast and weeds unique to the Northeast cropping systems. Currently participation includes IN, MI, IL and KY (Erin Haramoto will be an Assistant Professor there in August). Several participants noted that soil amendments appear to have little or no effect on weed seed mortality. They suggested that if our data shows this there is no reason to continue further along the lines of Objective 3. Renner suggested having multi-state, multi – locations on organic grower farms burying seeds into amended systems and seeing the short-term effect (1-9 months after burial) on seed mortality. This may be of interest if we find a weed species or an amendment that influences seed mortality. There was a discussion on including a soil biologist if we further pursue Objective 3 (and seed scientists) to determine how amendments influence seed mortality.

2014 NE-1047 Report Overview: We proposed a five year project (October 2011 to September 2016) that would 1) determine how soil conditions affect efficacy and selectivity of cultivation implements for the control of various weed species, 2) determine the reproductive growth stage at which summer annual weeds can be terminated and still produce viable seeds and quantify the effect of method of life-termination on seed production, and 3) determine the extent to which soil amendments such as green manures and compost affect seed mortality of various weed species. Although several investigators will continue to work individually on these objectives, multistate experiments following the same protocols are complete or will be completed in 2014 or by early 2015. A review of work conducted in 2014-15 is needed, primarily on the third objective, but the annual meeting in 2015 will focus on whether there is interest in continuing/renewing the project around the current objectives or developing a new line of research. Reports for 2013-14 were submitted by individual research teams, condensed, and are presented below. Objective 1: Determine how soil conditions affect efficacy and selectivity of cultivation implements for the control of various weed species. Two states participated in this objective: Maine and Pennsylvania. Since only two states participated and followed different protocols, this objective was not discussed during our meetings. The University of Maine research group conducted two field experiments related to Objective 1 in 2013. Cultivation efficacy and soil conditions were measured at 70 locations, randomly selected along five corn-row transects in a 2 ha field of silage corn. The cultivator was a common, older model, 3-point-hitch-mounted, 4-row Case International Model 183 with Danish s-tines and 10 cm sweeps and gage wheels. Condiment mustard, ‘Idagold,’ (Sinapis alba) was used as a surrogate weed. On June 11, 2013 (corn 10 cm tall, 2-leaf stage), Idagold was sown over the top of the corn at 5.5 kg ha-1 using a spin-spreader. Soil surface roughness was measured on June 26; samples to measure bulk density and texture were collected on June 26-27; soil moisture was measured on June 27. Pre-cultivation censuses performed on June 27, and the field was cultivated (mustard at 1- to 2-leaf stage); post-cultivation censuses were performed on June 29. Efficacy ranged from 5.8 to 100%, with mean and median values identical at 56%. This is 10% lower than efficacy in 2012 (mean and median efficacy in 2012 were 67 and 68%, respectively). Consistent with results from 2012, and contrary to expectations, soil conditions failed to explain any portion of the considerable variation in efficacy. Bivariate fits of mustard mortality with moisture, bulk density, soil moisture, surface roughness or texture failed to detect any relationships between our dependent and explanatory variables. It was surprising that the large amount of variability in efficacy was not related to measured soil conditions, despite relatively large ranges in these explanatory variables. Bulk density, for example, ranged from 0.7 to 1.47 g cc-1; soil moisture ranged from 20 to 37%; and surface roughness from 78 to 90 on a relative scale. Each census location was geo-referenced, and dependent as well as explanatory variables were subject to correlogram analysis to determine the effects of space. Correlation of mortality among census locations was generally low and consistent over the 80-meter distance range studied in this experiment. Soil parameters including surface roughness, bulk density and moisture likewise did not show a strong spatial signature for correlation over this scale (data not shown). Texture components, sand, silt and clay proportions, were, not surprisingly, negatively correlated among samples separated by 70 meters, but exhibited generally weak correlations at closer distances (data not shown). Completing two field seasons of research focused on site conditions, and having failed to detect any strong explanatory evidence from soil parameters studied, we aim to conclude this line of investigation and publish our results to date. In a separate field experiment condiment mustard was sown on four occasions, approximately at 3-day intervals, to establish a greater diversity in seedling size at the time of cultivation. Efficacy averaged 84%. As expected, efficacy was greatest for 1- and 2-leaf weeds (91 and 88%, respectively), intermediate for 3-leaf weeds (81%), and lowest for 4-leaf weeds (70%). This field experiment will be repeated in 2014, with the addition of several other surrogate weed species to initiate research on species-specific effects on efficacy variation. Specifically, we aim to examine two broadleaf and two grass species varying in seed mass and early seedling root:shoot allocation. Objective 2. Determine the reproductive growth stage at which summer annual weeds can be terminated and still produce viable seeds and quantify the effect of method of life-termination on seed production. Cornell University: Lambsquarters and giant foxtail were grown in soybeans summer of 2012 and killed at anthesis, when the first small green seeds formed or when the first black (LQ) or brown (GF) seeds formed. Plants were killed by chopping them into amall pieces, uprooting the plant or wiping the plant with glyphosate. Plants were placed in mesh bags to prevent loss of seeds and laid on the ground (chopped, uprooted) or left upright (glyphosate). Plants terminated at anthesis produced no or very few viable seeds. GF plants terminated at the first brown seed stage averaged about 4,000 viable seeds each and LQ plants averaged abut 2,000 each. Plants of GF terminated at the first green seed stage averaged over 400 seeds per plant when terminated with glyphosate but fewer than 10 if terminated by uprooting or chopping. LQ plants terminated at the first green seed stage averaged about 200 seeds regardless of treatment. Michigan State: Five summer annual species were terminated at three times (flowering, presence of immature seed, presence of mature seed) using three termination methods (cut at plant base, chopped into 10 cm sections, glyphosate). This project was conducted for two summers (2011 and 2012) with six replications each summer at the MSU Agronomy Farm in East Lansing, MI. At the time of termination plants were placed in mesh bags and either stored lying between soybean rows (cut and chopped samples) or left standing (glyphosate samples). All bags were retrieved in November of each year, at which time the viability of seeds recovered was determined using a combination of germination and tetrazolium testing. A subset of seed were returned to the field and retrieved again in March to determine the impact of overwintering on seed viability. Overall this study demonstrated that controlling escaped weeds during flowering is the best strategy for preventing additions to the seed bank. Canada thistle produced few viable seeds in both years of this study. Common lambsquarters, giant foxtail, jimsonweed*, and velvetleaf produced an average of 9,500, 390, 2,800*, and 370 seeds/plant when allowed to mature in corn and soybean fields. Controlling weeds when seeds were still immature reduced seed bank inputs by 80% or more compared to waiting until weeds had reached maturity. Rarely were differences among termination methods observed, however a trend in common lambsquarters towards increased seed production following a glyphosate application compared with cutting or chopping may warrant further investigation with an increased number of replications and multiple populations. Perhaps seed development is allowed to continue longer during the time it takes glyphosate sprayed weeds to desiccate and die. University of Maine: Due to budget and staffing limitations, the University of Maine research group did not conduct field experiments related to Objective 2 in 2013. University of Delaware: Methodology followed Michigan State; species examined were jimsonweed, giant foxtail, and velvetleaf. Unless weeds were killed at or very shortly after flowers, viable seeds were formed. Jimsonweed seed production was not consistently affected by termination methods. Velvetleaf and giant foxtail produced more viable seeds when cut than chopped or sprayed at the brown seed stage. Objective 3 results - Determine the extent to which soil amendments such as green manures and compost affect seed mortality of various weed species. Cornell – To explore the effects of cover crops on the survival of weed seeds in the soil, in Nov 2011 we buried mesh bags of common lambsquarters (LQ), Powell amaranth (PA), velvetleaf (VL) and giant foxtail (GF) seeds mixed with sand into plots of rye, hairy vetch or a bare control. Bags were recovered in May 2012 and either evaluated for viability or the contents mixed with the equivalent of 600 g per sq m of chopped cover crop and reburied. All plots had sorghum-sudangrass harvested as forage in the summer and were no-till planted with the same cover crops in Sep. Samples were recovered in May 2013 and treated as in 2012. Sorghum-sudangrass was again grown summer 2013 and cover crops planted in Sep. A third set of bags will be recovered in 2014, and a second set of seed bags was buried in Nov 2013. Viability did not differ between treatments in samples recovered in 2012. For 2013 samples, VL seeds survived better in rye than in hairy vetch or control. Marginally significant trends indicated LQ and PA seeds may have survived better in control than in hairy vetch, with intermediate survival in rye. This may be due to release of N from hairy vetch triggering inappropriate germination these nitrate sensitive species. Similarly, we (Bjorkman, Taylor) sequentially buried bags containing pigweed or foxtail seeds into living and killed buckwheat and sudangrass. Collected bags and assayed for sprouted, non-dormant, and dead seeds. Weed seed mortality was not affected by living cover crops or by their resides after the crops were terminated. Event the cyanide release from sudangrass during decomposition had no effect. Small changes in dormancy were observed but not enough to use for weed management. Purdue University: Methods followed those described above but lambsquarters, velvetleaf, and redroot pigweed were buried and recovered. Weed seed survival and germination was not affected by the cover crop treatments. Michigan State University (Brainard, Haramoto): Survival of buried weed seeds (Amaranthus powellii and Digitaria sanguinalis) was evaluated in a long-term trial examining the effects of cover crops (none, rye or rye-vetch) and tillage (moldboard plow vs strip-till) on weeds in a three-year vegetable crop rotation (sweet corn (2009, 2012): snap beans (2010, 2013): winter squash (2011, 2014)). Cover crop and tillage treatments have been imposed in the same plots since 2009. Seeds were buried following winter squash harvest in fall 2011, exhumed in spring 2012 and spring 2013, and tested for viability. Sufficient additional bags have been buried to examine survival for 2 additional years. One bag of each species from each plot was exhumed on 29 May 2013. Bags were stored at 4°C until they were opened, spread into a thin layer, and dried at room temperature. Seeds were separated from the sand and residue by sieving through a 500 µ sieve and stored at room temperature until viability testing. Seeds of both species were then germinated at 30°C with 2 µM GA. Ungerminated seeds were assessed for viability by a combination of squeeze testing and TZ testing. Seeds were characterized as germinated, dormant (did not germinate but were TZ viable), or dead; germinated and dormant seeds were considered viable. In moldboard plow treatments, all remaining bags were pulled prior to spring tillage, filled with a fixed amount of cover crop residue, and re-buried following tillage and planting the next day. Bags were filled with rye and vetch residue that had been collected prior to termination (15 May 2013), dried down, and coarsely ground in a Wiley mill. Pieces of ground residues were approximately 5-10 mm long. Experiment-wide, dry rye biomass averaged 2400 kg/ha in rye only plots and 2940 kg/ha with 560 kg/ha vetch biomass in rye/vetch plots. For rye plots, we added 0.13 g of dry rye residue per bag; for rye and vetch plots we added 0.13 g dry rye and 0.027 g dry vetch residue. Results. In 2013, more viable AMAPO seeds were recovered from ST than from MBP; 43% of AMAPO seeds recovered in ST were still viable while only 4% of those recovered from MBP were viable. Within each tillage type, the cover crop species did not affect AMAPO viability. Seeds within MBP were excavated and mixed with cover crop residue (or just mixed to stimulate tillage for plots without cover crops) in June 2012, while those in ST were buried continuously since November 2011. It is possible that removal and reburial of seeds in MBP treatments promoted more fatal germination than ST treatments due to greater exposure to light, oxygen or other germination stimuli. In 2013, no effects of tillage or cover crop on DIGSA viability were detected, and survival was less than 10% in all cases. Large variability in DIGSA survival—especially in strip-tillage treatments—limited our ability to detect significant differences. Michigan State University (Renner, Hill): Lambsquarters, giant foxtail, velvetleaf were buried as described above but a higher rate of cover crop biomass, equivalent to 6.2 g DW per bag, was used and bags were recovered at 0, 1,2,4,6, and 12 months. Legure cover crops did not increase weed seed mortality compared to the no cover-crop treatment. High rates of rye appeared to increase weed seed persistence.

Kordbacheh, F., C.L. Mohler, A. DiTommaso, and H. Rahimian Mashhadi. 2013. Effects of different cutting methods and timing on seed viability and germination of three annual weed species. Abstracts from the Joint Annual Meeting of the Weed Science Society of America and Northeastern Weed Science Society. February 4-7, Baltimore, MD. No. 195. Mohler, C.L., B. Caldwell, C. Marschner, and A. DiTommaso. 2013. Mortality of weeds due to tine weeding and inter-row cultivation in corn and soybeans. Abstracts from the Joint Annual Meeting of the Weed Science Society of America and Northeastern Weed Science Society. February 4-7, Baltimore, MD. No. 248. Bellinder, R. 2013. Herbicide research report for processing vegetables. Proceedings of the Empire State Producers Expo January 22-24, 2013, Syracuse, NY. Bellinder, R. 2013. Evaluating new herbicides for cabbage—2012. Proceedings of the Empire State Producers Expo January 22-24, 2013, Syracuse, NY. Mohler, C. L. 2013. Webinar: Crop rotations for Diversified Farms. NRCS, Portland OR Office. Given June 8, 2013. On line at http://conservationwebinars.net/webinars/crop-rotations-on-diversified-farms