October 19, 2012 - Kansas State University · October 19, 2012 1. ... primary postemergence tank-mix options would be Cobra, ... The Vegetation Condition Report for Kansas for October

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Number 373 October 19, 2012 1. Preharvest glyphosate treatment on sorghum: Effect on subsequent wheat yields 2. Planning ahead for weed control in Roundup Ready soybeans 3. Comparative Vegetation Condition Report: October 2 – 15 1. Preharvest glyphosate treatment on sorghum in a no-till system There have been numerous questions this fall on effective ways to manage grain sorghum to improve the performance of winter wheat planted into no-till sorghum residue following fall harvest. The technique most often asked about is applying glyphosate to the sorghum crop prior to harvest. Most glyphosate labels require that applications be made to the sorghum crop when grain moisture is at 30% or less to minimize any possible yield reductions, and there is a seven-day period between time of application and harvest. We established three trials – at Belleville, Manhattan, and Ottawa – in 2011 to test the effect of a pre-harvest treatment of glyphosate on grain sorghum and wheat yields. Below are two figures comparing grain yield and moisture of sorghum treated with glyphosate and untreated sorghum.

Glyphosate was applied to the above sorghum crop when grain moisture was approximately 18-21%, and the grain was harvested 7-10 days following the application. Average yield reduction to the sorghum crop when sprayed with glyphosate was about 2-3 bushels or roughly 2% less than untreated.

Figure 1. Grain sorghum yields of sorghum treated with preharvest glyphosate and sorghum with no glyphosate application.

Figure 2. Grain moisture of sorghum treated with glyphosate preharvest and sorghum with no glyphosate.

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Wheat had positive yield responses to preharvest glyphosate applications at all three locations. Grain protein was also increased at two of the three locations. Figures 3 and 4 show yield results from the 2012 wheat crop:

When glyphosate was applied to the sorghum preharvest, wheat yielded 12-13% more on average than wheat following untreated sorghum. That is equivalent to an average increase of about 5-6 bushels for the wheat crop. Applications of glyphosate to grain sorghum prior to fall harvest can help improve the performance of the following wheat crop. It is important to follow the glyphosate label for application recommendations. Glyphosate applied at low rates or when temperatures are not adequate may reduce the effectiveness of the product. The sorghum field should also be inspected for stalk issues prior to applying the glyphosate. If stalk rots are present, applying glyphosate may increase the chance of plant lodging if it is not harvested in a timely manner. -- Josh Jennings, CCA – Graduate Research Assistant, Agronomy [email protected] -- Kraig Roozeboom, Cropping Systems Agronomist [email protected] 2. Planning ahead for weed control in Roundup Ready soybeans Fall harvest is a good time for producers to assess the weed problems they had in soybean fields this year, to plan a good weed control program for next year. In most cases now, it is no longer possible to rely strictly on glyphosate for broadleaf weed control in Roundup Ready soybeans. Before deciding which other herbicides should be used in addition to glyphosate, it is necessary to know what weeds are being targeted. Some good options for the most common broadleaf weed and grass problems include: * Pigweeds (including waterhemp and Palmer amaranth). Glyphosate-resistant waterhemp has exploded across eastern Kansas in recent years, and it appears glyphosate-resistant Palmer amaranth is now starting to show up as well. Glyphosate-resistant Palmer amaranth is a major problem in the southeastern U.S. and has forced producers there to make dramatic changes in their weed management programs. For preemergence pigweed control, the Valor-based herbicides (Valor SX,

Figure 3. 2012 wheat yields follow grain sorghum treated with glyphosate and sorghum with no glyphosate treatment.

Figure 4. Grain protein of wheat following grain sorghum treated with glyphosate and sorghum with no glyphosate treatment.

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Valor XLT, Fierce, Gangster, Envive, and Enlite) and Authority-based herbicides (Authority XL, Authority First, Sonic, Authority Assist, Authority MTZ, and Spartan) can all provide very good to excellent control to supplement a postemergence program. Prefix is another excellent “foundation” herbicide for residual pigweed control in soybeans. Intrro, Dual, Outlook, and Prowl products can also provide some early-season pigweed control, but generally are not as effective as those previously mentioned products. Although some of these herbicides can be applied in the fall or early spring, those treatments generally will not persist long enough to give good pigweed control into the soybean growing season. So if pigweed is the primary target, treatments will be most effective if applied no more than two weeks prior to planting. If glyphosate-resistant pigweeds escape preemergence control, the primary postemergence tank-mix options would be Cobra, Flexstar, or Ultra Blazer. However, timing is critical for good control. These products should be applied before pigweeds exceed 4 inches tall. * Velvetleaf. Glyphosate is not always entirely effective on velvetleaf. To assist in velvetleaf control, the Valor-based and FirstRate-based herbicides (Valor SX, Valor XLT, Fierce, Gangster, Authority First, and Sonic) are some of the most effective preplant and preemergence herbicides you can use. * Cocklebur. The most effective preplant and preemergence herbicides to aid in cocklebur control are those that contain First Rate, Classic, or Scepter. Such products would include Authority First, Sonic, Gangster, Envive, and Valor XLT. Extreme, which is a premix of glyphosate and Pursuit, can also be used as a preplant or postemergence treatment in Roundup Ready soybeans to provide residual cocklebur control. However, all of these herbicides are ALS-inhibiting herbicides, and ALS-resistant cocklebur may be present in some fields. * Marestail. Marestail is probably the most widespread glyphosate-resistant weed in Kansas. Marestail control in fields going to soybeans should begin with fall or early spring herbicide treatments that include 2,4-D, Clarity, or an ALS-inhibiting herbicide such as Canopy EX. Fall treatments should be delayed until November when most of the fall-germinating marestail has emerged. Be aware of the intervals required between application of these herbicides and planting soybeans. A couple of relatively new options for marestail control in soybeans without a preplant waiting interval are the Kixor-containing products, Sharpen and Optill. Sharpen is Kixor alone, while Optill is a premix of Kixor and Pursuit. Both products can be used for burndown control of marestail anytime before soybean emergence (cracking). To optimize marestail control with Sharpen and OpTill, spray before marestail gets too big, use an adequate spray volume to insure good spray coverage, and apply in combination with a methylated seed oil. The Kixor rates that can be used in soybeans will not provide very much residual control of marestail. Other residual preplant herbicides that can help with burndown and residual marestail control include Valor and FirstRate-based herbicides, such as Valor XLT, Envive, Enlite, Authority First, Sonic, or Gangster. Marestail is best controlled before soybean planting and before the marestail begins to bolt. FirstRate or Synchrony would probably be the most effective tank-mix partner with glyphosate for postemergence marestail control in Roundup Ready soybeans. Liberty is one of the better herbicides to control marestail that has started to bolt in the spring. Liberty can be used as a burndown treatment prior to emergence of any soybeans, or as a postemergence treatment in Liberty Link soybeans.

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* Morningglory. Glyphosate sometimes has trouble controlling morningglory. To help get better control, you can use either Authority-based or Valor-based herbicides preplant or preemergence. Liberty can also provide good control of soybeans in Liberty Link soybeans. * Kochia. Kochia is a major weed problem in western areas and has often been difficult to control with glyphosate, especially as it gets bigger. In addition, glyphosate-resistant kochia is becoming a major problem in western Kansas. Since much of the kochia emerges well before soybean planting, one of the keys to managing kochia in soybeans is to control it early in the spring before soybean planting. Research by K-State the last couple of years indicates that several preemergence herbicides can help provide control of glyphosate-resistant kochia, especially the Authority-based products listed above. Early applications of Clarity can also provide effective control of kochia, but the appropriate precipitation and preplant waiting intervals need to be followed to avoid potential soybean injury and stand loss. The Kixor-containing products Sharpen and Optill may help with kochia burndown, but the Kixor rates that can be used in soybeans will not provide very much residual control. ALS-inhibiting herbicides may or may not provide kochia control because of the occurrence of ALS-resistant kochia. * Crabgrass and small-seeded broadleaf weeds. Glyphosate usually gives good control of most grasses, but producers may want to apply a foundation herbicide to control grasses early, followed by a postemergence glyphosate application to clean up any escapes. Prefix, Fierce, Intrro, Dual II Magnum, Outlook, and Prowl H2O can all provide good early-season grass and pigweed control ahead of Roundup Ready soybeans. Of these, Prefix and Fierce generally provide the best pigweed control, and Prowl H20 the least. Several residual herbicides, such as Warrant, Outlook, and metolachlor products can be applied as a postemergence tank-mix with glyphosate to provide extended residual control of grasses and broadleaves later in the season. However, it is important to understand that these products do not have postemergence activity, so they will not control emerged glyphosate-resistant pigweeds. -- Dallas Peterson, Weed Management Specialist [email protected] -- Doug Shoup, Southeast Area Crops and Soils Specialist [email protected] 3. Comparative Vegetation Condition Report: October 2 – 15 K-State’s Ecology and Agriculture Spatial Analysis Laboratory (EASAL) produces weekly Vegetation Condition Report maps. These maps can be a valuable tool for making crop selection and marketing decisions. Two short videos of Dr. Kevin Price explaining the development of these maps can be viewed on YouTube at: http://www.youtube.com/watch?v=CRP3Y5NIggw http://www.youtube.com/watch?v=tUdOK94efxc The objective of these reports is to provide users with a means of assessing the relative condition of crops and grassland. The maps can be used to assess current plant growth rates, as well as comparisons to the previous year and relative to the 21-year average. The report is used by

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individual farmers and ranchers, the commodities market, and political leaders for assessing factors such as production potential and drought impact across their state. NOTE TO READERS: The maps below represent a subset of the maps available from the EASAL group. If you’d like digital copies of the entire map series please contact Kevin Price at [email protected] and we can place you on our email list to receive the entire dataset each week as they are produced. The maps are normally first available on Wednesday of each week, unless there is a delay in the posting of the data by EROS Data Center where we obtain the raw data used to make the maps. These maps are provided for free as a service of the Department of Agronomy and K-State Research and Extension. The maps in this issue of the newsletter show the current vegetation conditions in Kansas, the Corn Belt, and the continental U.S, with comments from Mary Knapp, state climatologist:

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Map 1. The Vegetation Condition Report for Kansas for October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that the eastern portions of Kansas benefited the most from the recent rains. While freezing temperatures have occurred in the area, the lows were not unusually cold or prolonged, so photosynthetic activity remains high. In far northeast Kansas, the combination of early harvest and impacts from previous flooding have caused photosynthetic activity to be relatively low compared to surrounding areas.

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Map 2. Compared to the previous year at this time for Kansas, the current Vegetation Condition Report for September October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows the southern third of the state is faring slightly better than the northern third, relative to conditions last year at this time. Remember, last year at this time most of the southern half of the state was in exceptional drought, while the northern parts of the state were just entering drought.

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Map 3. Compared to the 23-year average at this time for Kansas, this year’s Vegetation Condition Report for October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that Ness County, in western Kansas, is above average to the greatest extent in terms of biomass production. East central and southeast Kansas are also slightly above average in photosynthetic activity for the period.

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Map 4. The Vegetation Condition Report for the Corn Belt for October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that southern and eastern edges of the region have the greatest photosynthetic activity. The Missouri Boot Heel continues to be an exception. While drought conditions in southern Missouri continue to improve, the Boot Heel region remains in extreme drought.

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Map 5. The comparison to last year in the Corn Belt for the period October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that some areas of Kansas and Missouri have slightly increased photosynthetic activity. This reflects areas that have benefited from recent rains. The majority of the region is well below last year’s level of photosynthetic activity. Reports from northern Michigan and Minnesota have many of the trees already losing their leaves.

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Map 6. Compared to the 23-year average at this time for the Corn Belt, this year’s Vegetation Condition Report for October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that the biggest departures from average are in northern Minnesota and northwestern Michigan. Drought impacts and early harvests have reduced the normal level of photosynthetic activity.

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Map 7. The Vegetation Condition Report for the U.S. for October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that the highest photosynthetic activity is in the South and along the Pacific Northwest. The Mississippi River Valley is a notable exception in the South. In the Mississippi River Valley, the combination of early harvest, and impacts from previous flooding have caused photosynthetic activity to be relatively low compared to surrounding areas.

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Map 8. The U.S. comparison to last year at this time for the period October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that Texas has much higher NDVI values than last year at this time. Currently, only 3 percent of the state is in exceptional drought. Last year at this time 73 percent of the state was experiencing exceptional drought.

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Map 9. The U.S. comparison to the 23-year average for the period October 2 – 15 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that the Upper Plains has the biggest departure from average NDVI values. Early harvest in the region is a major factor in these values. In South Dakota, 90 percent of the corn has been harvested compared to a 5-year average of 22 percent. -- Mary Knapp, State Climatologist [email protected] -- Kevin Price, Agronomy and Geography, Remote Sensing, Natural Resources, GIS [email protected] -- Nan An, Graduate Research Assistant, Ecology & Agriculture Spatial Analysis Laboratory (EASAL) [email protected] These e-Updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e-Update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, 785-532-7105 [email protected], Jim Shroyer, Crop Production Specialist 785-532-0397 [email protected], or Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist 785-532-3444 [email protected].