There has been a lot of wheat harvested in the area over the past seven to 10 days. Some of those acres will go into double crop soybeans. Some wheat fields have significant weed populations that remain after harvest, and many wheat fields have at least some marestail weeds present. This week, Mark Loux, OSU Extension weed specialist provides recommendations on controlling marestail and other weeds in post-harvest wheat fields preparing for double crop soybeans.

"There can be a couple types of marestail plants to deal with in this situation: 1) small ones that were lurking near the base of the wheat plants, and largely not disturbed by the combine; and 2) larger ones that get cut off by the combine and then regrow. The first of these is really the ideal situation because the small undisturbed plants can usually be controlled by one of the following: glyphosate plus Sharpen + MSO; glufosinate (Liberty, Interline, Cheetah, etc.); or possibly even Gramoxone plus metribuzin (although this is more effective when mixed with 2,4-D). Adding metribuzin to any of these can improve control of emerged marestail and provide some residual control of later emerging marestail as well.

The second situation, where marestail plants regrow following damage by the combine, is more challenging. We have tried a number of treatments at multiple locations where marestail have been in this condition, and have not been able to obtain more than about 80% control. This level of control can prevent competition with the soybeans and minimize seed production. Best options for this situation, ranked from most to least effective:

Glufosinate + Sharpen + metribuzin + MSO

Glufosinate + Sharpen + MSO

Glyphosate + Sharpen + metribuzin + MSO

Glyphosate + Sharpen + MSO

A few other things to consider:

• Glyphosate treatments may be the better choice where large grasses are present, or where grasses other than giant foxtail are present.

• All of these treatments contain one or more contact herbicides (not systemic) and should be applied in at least 15 gallons per acre volume with the appropriate nozzle and adjuvants to ensure thorough coverage.

• Planting LibertyLink soybeans provides more flexibility in when glufosinate can be applied, and provides for the postemergence use of glufosinate. Do not wait too long after soybean planting to apply the glufosinate because the marestail won’t get any easier to control. In Roundup Ready or non-GMO soybeans, there are no effective postemergent options for marestail control.

• The preemergence burndown is responsible for much of the weed control in double crop soybeans, and we advise against trying to go too simple or inexpensive. Adding some residual herbicide is not necessarily a bad thing in double crop, but it is not near as important compared with full-season soybeans. Additionally, carryover concerns dictate that no application of some residual soybean herbicides this late in the season where corn will be planted next year. Products containing chlorimuron, cloransulam, imazaquin, or imazethapyr fit in this category.

• Much of this information also applies to control of marestail in wheat stubble, in the absence of soybeans. However, 2,4-D can be used in wheat stubble, and also dicamba if the temperatures are cool enough. Our research in wheat stubble has shown that applying before the end of July is more effective, and even glyphosate/2,4-D can prevent most of the seed production if applied by then. Preventing marestail seed production is the goal in wheat stubble. The marestail plants present in July following wheat harvest will not survive through the winter, and any chemical or nonchemical approach that prevents them from flowering and producing seed is adequate." Water vital to summer livestock management

In a recent OSU Extension Beef Cattle Letter article, Aerica Bjurstrom, a University of Wisconsin Extension educator, makes the following points about water for beef cattle during the summer:

• A University of Georgia publication suggests for cattle in 90 °F temperatures, a growing animal or a lactating cow needs two gallons of water per 100 pounds of body weight. A nonlactating cow or bull needs one gallon of water per 100 pounds of body weight. Using these figures, a single cow/calf pair can require roughly 25 to 40 gallons of water daily.

• Water quality is just as important as water volume intake. Compromised quality can reduce water intake, which can lead to illness and metabolic issues. Testing water for salinity, nitrates, and sulfates is recommended.

• Guidelines suggest that water containing 3,000 ppm TDS (total dissolved salts) or less is usually acceptable for most livestock. In addition, water with salinity over 5,000 ppm TDS can act as a laxative and dehydrate cattle.

• Nitrates pose another issue for cattle. A safe level of nitrate nitrogen (NO3N) in the water for cattle is less than 100 ppm.

• The safe upper limit of sulfate consumption is 500 mg/L (ppm) (167 ppm sulfur as sulfate). Unsafe levels of sulfates may lead to polioencephelomalacia (PEM), a brain disorder in cattle, and cause digestive absorption issues. Read the entire article on-line at http://go.osu.edu/watervital

Rory Lewandowski is an OSU Extension agriculture and natural resources educator and may be reached at 330-264-8722.