April 27, 2007

Section 18 Exemption Granted

Considerations for Using Lumax in Grain Sorghum

• The maxium use rate per growing season is 2.5 qt/ac.
• Lumax may be applied in three scenarios:
  1. 2.5 qt/ac, 7-14 days preplant;
  2. 1.5 qt/ac 10-14 days preplant and 1 qt/ac preemergence; or
  3. 1.25 qt/ac 10-14 days preplant and 1.25 qt/ac preemergence.
• The exemption is effective immediately and lasts until June 15, 2007.
• Sorghum should not be harvested within 60 days of Lumax application.
• Retailers selling Lumax for use on grain sorghum must first obtain a permit from the Nebraska Department of Agriculture.
• Any individual applying Lumax to grain sorghum should have a copy of the Section 18 label with them (see box). Only certified applicators or persons under their direct supervision may buy and apply this product, and only for those uses covered by the certified applicator’s certification.
• Lumax is a restricted use pesticide due to surface and ground water concerns. Both atrazine and S-metolachlor, active ingredients in Lumax, are known to move into surface and ground water sources. Refer to the label for specific restrictions in fields with highly erodible soils or adjacent to intermittent and perennial streams and rivers, lakes, tile-outlets, and wells.

Instructions for Accessing Section 18 Label On-line Growers can access the Lumax on Sorghum Indemnified Section 18 (Nebraska) label by registering at http://www.farmassist.com and completing the steps outlined by Syngenta below. Go to the http://www.farmassist.com Web site. If first time user, register as a new user. On the left side of the screen select Syngenta Crop Protection then Products then Special Labels At the top of the ensuing screen, click the "here." (If searching for indemnified labels, click here.) Click the Section 18 box, select Nebraska, select Lumax Click the Submit button near the bottom. On the next window you should see information on the Section 18. Then click on sorghum. Final step is to accept the terms and conditions of the indemnified label by clicking on the “I accept” button. Now the label will be available for viewing and printing. Note: If you have trouble getting the label, make sure you did not miss Step 4. If you still have difficulty, call the Syngenta Customer Resource Center at 866-796-4368.

Lumax contains three active ingredients: mesotrione, S-metolachlor, and atrazine. It can provide season-long control of many broadleaf and grass weeds. Sorghum producers have used S-metolachlor (Dual II Magnum) and atrazine (Aatrex and other brand names) both individually, and as a premix (Bicep II Magnum), for many years in preplant, preemergence or postemergence herbicide applications. The new compound in this mix is mesotrione.

Mesotrione is the active ingredient in Callisto (a herbicide labeled for use in corn). It has preemergence and postemergence activity on broadleaf weeds. Mesotrione kills sensitive plants by limiting carotenoid biosynthesis. Sensitive plants may turn white or pale yellow before dying. For that reason, herbicides like mesotrione are sometimes called “bleachers.”

Because Lumax contains both atrazine and mesotrione, it has some activity on emerged weeds; however, Lumax alone is not adequate to control emerged weeds larger than 3 inches. If the field requires a burndown treatment 7-14 days preplant, Lumax may be tank-mixed with a glyphosate product or 2,4-D. In glyphosate + Lumax tank mixtures, add ammonium sulfate (AMS) at 17 lb/100 gal. Many generic glyphosates also require adding a non-ionic surfactant (NIS) at 0.25% v/v. Refer to the product label of each tank-mix partner for specific requirements.

Lumax may be applied with a liquid fertilizer carrier for preplant applications. Always perform a compatibility test with the fertilizer carrier and Lumax prior to loading the spray tank. Even if Lumax and the fertilizer are compatible, constant agitation is necessary to maintain a uniform mixture. Tank-mixing a burndown herbicide (glyphosate or 2,4-D) with a Lumax-N fertilizer carrier solution is not recommended. The burndown herbicide should be applied separately.

Like most soil-applied herbicides, Lumax must be activated by rainfall (about 0.5 inch) or sprinkler irrigation to effectively control weeds. If activation is delayed past 7-10 days, some weeds may emerge and grow large enough to be unaffected when the herbicide is activated. In this case a cultivation or postemergence application of another herbicide may be necessary. If it is activated within 7-10 days, Lumax will generally provide season-long control of most weeds.

The basis for the Section 18 exemption request was that sorghum producers struggle to adequately control ALS-resistant common waterhemp and triazine-resistant Palmer amaranth. Mesotrione has good to excellent activity on these two species, as well as other difficult to control weeds such as velvetleaf, sunflower, lambsquarters, Russian thistle and kochia. Large crabgrass is the only grass species common to Nebraska that it consistently controls.

Grain sorghum producers who are most likely to benefit from using Lumax are those who

1. want a one-pass herbicide program and
2. have a broadleaf weed pressure that is not adequately controlled by preemergence herbicides like Bicep II Magnum, Bullet, and Guardsman Max.

Tests conducted by University of Nebraska-Lincoln (UNL) weed scientists have shown that Lumax provides equal or superior control of most weeds as Bicep II Magnum and comparable herbicides.

As a caution, grain sorghum can be sensitive to injury from mesotrione. Injured plants turn pale yellow or white. The affected leaves remain white until they senesce, but as the plants continue to grow, new tissue is green. In UNL research we did not observe yield loss from minor early-season injury. The risk of injury is minimal when Lumax is applied at labeled rates before crop emergence. The risk of injury increases when Lumax is applied at above label rates (for example, if a sprayer is not calibrated correctly), in areas where sprayer overlaps occur, or when Lumax is applied too close to the time of emergence.

Mark Bernards
Extension Weeds Specialist
Bob Klein
Extension Crops Specialist

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