MN Fruit & Vegetable IPM News - Vol. 3, No. 3

You may have seen the new herbicides advertised by Syngenta for use on processing and fresh market sweet corn, products with such exotic sounding names as Lumax, Lexar and Camix. These products are pre-packaged mixtures with Syngenta's Callisto herbicide (mesotrione). If you also grow field corn, you may already be familiar with Callisto. Callisto is a member of an evolving group of herbicides for use on field corn, popcorn, and sweet corn that are carotenoid inhibitors (HPPD inhibitors). Other products in this herbicide mode of action group are Balance, Command, and the new product from AMVAC, Impact (topramezone). Impact and Callisto are now labeled for use on sweet corn. Both products provide complete broadleaf weed control with the addition of reduced rates of atrazine. Both products do pose a carryover risk to many of our rotational vegetables. Both products offer new potential to control broadleaf weeds in sweet corn.

Callisto package mixtures Camix, Lumax and Lexar contain Dual II Magnum (s -metolachlor). In addition, Lumax and Camix also contain atrazine – each with a unique ratio of the respective herbicides. These package mixtures are for preemergence use only on sweet corn. Postemergence applications of Callisto in particular may cause some temporary yellowing of sweet corn leaves shortly after application, but generally has no affect on yield or on growth and development of sweet corn. However, postemergence applications do provide more effective and consistent broadleaf weed control than soil applied applications. Postemergence applications need adjuvant additives, soil applied applications do not.

For Minnesota, tank mixes of 3 oz of Callisto with atrazine at 0.27 to 0.55 lb/A 90 DF product postemergence, or 6 to 7.7 oz. Callisto soil applied preemergence with 0.55 to 0.83 lb 90 DF product provide good control of most broadleaf weeds. Postemergence applications of Callisto must be applied with adjuvant additives to improve performance. If you have used Callisto in field corn, you likely have used Callisto with UAN fertilizer additives and with crop oil concentrate.

For sweet corn, research has shown that the best compromise to improve sweet corn crop tolerance, yet maintain weed control is to apply Callisto postemergence with nonionic surfactants. Crop oil concentrate can be used to improve weed control during extreme conditions such as dry weather, or if the predominant weed species are species on which Callisto is less affective. UAN nitrogen fertilizer should never be added to Callisto when applied postemergence to sweet corn. Where no atrazine will be used, crop oil concentrate can improve the performance of Callisto to gain more complete broadleaf control. Callisto can be applied up to 8-leaf sweet corn. If atrazine is used in the tank mixture, the atrazine restrictions of a 12-inch corn height cutoff must also be followed. There is a 45-day preharvest interval for Callisto. Callisto is very effective on velvetleaf and also controls common lambsquarters, pigweeds, and Eastern black nightshade. Callisto will also provide some suppression of Canada thistle. Adding atrazine improves the control of ragweeds, kochia, wild buckwheat, and cocklebur, and gives a little extra residual control of broadleaf weeds. The addition of atrazine also gives a little improvement of grass activity. Callisto itself does not provide complete grass control and should be used with a grass herbicide for a broad-spectrum weed control program.

Package mixtures advertised recently include Camix, Lumax, and Lexar

- 2.4 qts/A of Camix = 2 lbs a.i. of metolachlor and 0.2 lb a.i. of mesotrione

- 3 qts/A of Lumax = 2 lbs a.i. of metolachlor plus 0.75 lb a.i. of atrazine plus 0.2 lb a.i. of mesotrione

- 3 qts/A of Lexar = 1.3 lbs a.i. of metolachlor plus 1.3 lbs of atrazine and 0.168 lb a.i. of mesotrione

As you can see, the different package mixtures offer different ratios of product. Camix prepackage mixtures include no atrazine. Lumax and Lexar include atrazine with a more aggressive rate of atrazine included in the Lexar package mix. Prepackage mixtures provide convenient and economical ways to purchase the various products including metolachlor (Dual), a mainstay grass control acetanilide herbicide used widely in processing and fresh market sweet corn.

Camix, Lumax, and Lexar should only be applied preemergence to sweet corn. These package mixtures can be preplant surface applied up to 14 days before sweet corn planting or applied preemergence after planting sweet corn. Use Camix at 2 qts per acre on soils of less than 3% organic matter and at 2.4 qts per acre on soils with greater than 3% organic matter. Lumax should be used at 2.5 qts per acre on soils with less than 3% organic matter and at 3 qts per acre on soils with greater than 3% organic matter. The ratio of the herbicides in Lexar is not as well suited for use in Minnesota weed spectrums, soil types, and rotations as the ratios in Camix and Lumax. For those of you with severe pressure of common ragweed, the mixtures with atrazine would be recommended as Callisto alone or the use of Camix without the addition of atrazine may provide only suppression of common ragweed. Another similar issue would occur with heavy populations of kochia, giant ragweed, and wild buckwheat. Wisconsin research has shown that below labeled rates of 5 to 6 oz of Callisto tank mixed with 0.83 lbs atrazine 90 DF have worked well in sweet corn trials when applied preemergence. Remember that preemergence applications rarely result in bleaching injury more commonly seen with postemergence applications of Callisto, but the spectrum of weed control is typically decreased.

Callisto herbicide does interact with organophosphate insecticides. Callisto should not be tank-mixed with organophosphate insecticides. Organophosphate insecticides should not be applied within 7 days of Callisto applications. Finally, Callisto should not be used at all if the insecticides Counter or Lorsban are used due to increased risk of unacceptable sweet corn injury.

Finally, Callisto does have residual carryover. The extent of carryover was discovered the hard way with considerable carryover to peas after the initial introduction of Callisto use on field corn. Be sure to follow rotation restrictions on the Callisto label. Several crops are sensitive to Callisto and remember, any crop that is not specifically listed on the label does fall into the 18-month rotation interval. Specifically, the 18-month rotation interval does apply for pea, dry beans, snap beans, and beets. Crops and forages, such as corn, soybean, potato, and alfalfa carry a 10-month rotation restriction. Small grains carry a 120-day rotation restriction.

The other new carotenoid inhibiting herbicide labeled for use in sweet corn is Impact (topramezone) marketed AMVAC. Impact is another herbicide that producers who grow field corn will recognize. The biggest issue with Impact in Minnesota is carryover and injury to soybeans. Because of the 18-month rotational restriction on soybeans with the 0.75 oz/A full use rate of Impact, a supplemental label is issued for use east of Hwy 71 in Minnesota. The supplemental label is for the use of Impact at a reduced 0.5 oz/A of product. The full-labeled rate of Impact, 0.75 oz of product per acre, provides more consistent control of more broadleaf weed species but does markedly increase the risk of carryover to sensitive crops. Impact can be applied postemergence from emergence until 45 days before corn harvest. Methylated soybean oil or crop oil concentrate plus nitrogen additives are recommended for use with Impact on sweet corn. Impact typically would be used at 0.5 oz product per acre with 0.55 to 0.83 lb/A atrazine 90 DF, with 1% v/v methylated soybean oil, and 2.5% v/v UAN.

Impact also has a 45-day preharvest interval. Rotation restrictions on Impact at the 0.75 oz./A rate are 3 months for small grains, 9 months for alfalfa and potato, and 18 months for soybeans and all other crops. The supplemental label for the reduce 0.5 oz. reduces the soybean rotation restriction to 9 months, but does not address changing the rotation restrictions for any other crop, thus most vegetable crops you may be rotating to require an 18 month rotation restriction.

Another experimental product on the horizon similar to Callisto and Impact is a product by Bayer currently called by an abbreviated form of its experimental number, 747. 747 is under study in Wisconsin and Minnesota trials and information will be available in the future should it be labeled.

For any of these herbicide products, be sure to consult the label for specific use rate and additive instructions. Always follow labeled restrictions and labeled rotational guidelines. As always, the label supersedes information contained in this, or any press article.

For more information, visit the UofM's Applied Weed Management site, at: http://appliedweeds.coafes.umn.edu/

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ACKNOWLEDGEMENTS

Co-Editors: Bill Hutchison (hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness (woldx018@umn.edu), Department of Entomology, University of Minnesota

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jean Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us, MDA, 625 Robert St. North, St. Paul, MN 55155-2538. You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: http://www.mda.state.mn.us/ipm/ipmnews/

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture – Risk Management Agency (RMA). These institutions are equal opportunity providers.

DISCLAIMER

Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current manufacturer directions.

The University, including the Minnesota Extension Service, is an equal opportunity educator and employer. ©1999-2006 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.