Straight from the Horse's Mouth

Duane A. Lienemann, UNL Extension Educator, Webster County October 16, 2009 Edition We have been seeing an influx the last several years of winter annuals that have worked their way into lawns, garden areas and even crop fields. Those lawn weeds in the winter annual category include that ugly purple flowered plant called Henbit, as well as Chickweed, Black Medic, Oxalis, Pepperweed, and White Clover. Winter annual broadleaf weeds in crop fields include the same Henbit we find in lawns, as well as Marestail and several species of Mustards, such as Field Pennycress, Shepherds Purse, Tansy Mustard, Blue Mustard, etc. What makes this weed a “Winter Annual” is that it germinates in the fall, overwinters as a green plant, begins growing again in early spring, then completes their life cycle and go to seed in the spring or early summer. These weeds have become more of a problem each year and in fact Henbit was all over the place last spring and I expect to see even more this year. One of the most often asked questions for lawns and crops is “When is the best time to control these weeds?” Well, right now or even a little later is a pretty good answer. According to Dr. Bruce Anderson, UNL Forage Specialist, the best time to apply post-emergent control measures to winter annuals is in the fall when the seedling plants are small and the plant has not had time to store much energy in the root system. Timing is not critical, so there is an extended window to apply herbicides especially when harvest may be a little late for crop producers. Best control will be achieved if daytime temperatures are above 60 degrees, but good control can be obtained even when temperatures are in the 50s most years. Anderson indicates that too often, farmers and/or homeowners wait until spring to attempt control of winter annual weeds. Unfortunately, several factors are working against you in the spring. In the early spring, the weather is more unpredictable. It can be warm one day and cold the next. Another factor is the growth stage of winter annual weeds. In the spring, winter annuals are in the reproductive mode. They bolt quickly, flower and before you know it, they are setting seed. The plant is larger with a more developed root system and is flowering, so is less likely to receive a lethal dose of herbicide from your application. In the fall, the weather usually is more cooperative and weeds are in the rosette, or vegetative stage and more susceptible to herbicides. Winter annuals can typically be sprayed from late September to early December, weather permitting. As far as rates are concerned, fall applications typically require less herbicide and thus are less expense. Make sure that you follow label rate recommendations and remember that Atrazine is not labeled for fall application in Nebraska. The common winter annuals can be readily controlled with the following products: Crop production field applications: 1.5 to 2 pints of 2,4-D ester per acre ; 1 pint 2,4-D and 4 ounces dicamba per acre; 24 ounces of glyphosate per acre; 1 pint 2,4-D and 16 ounces glyphosate per acre. Home lawn applications: selective, 3-way products, such as Trimec, Triamine or Ortho Weed-B-Gon, containing herbicides like 2, 4-D, dicamba and MCPP. Since we are talking controlling weeds, how about those thistles? Gosh I wish I had a dollar for every one of those evil things I have cut or dug up. Well, timing is everything and that's particularly true with thistle control. October to early November is one of the best times to use herbicides for thistle control. If you had a thistle problem this year, check infected areas for the small, flat rosette seedlings typical of fall growth. Seedlings are especially sensitive to certain herbicides and are more effectively controlled in the fall so this time of year is perfect to control them. There are several products out there. Milestone, one of the newer herbicides, is very effective from tests that I have seen. Two other effective old standby herbicides are of course Tordon 22K and Grazon. You need to be careful with them however, as they can also kill woody plants, including trees. While it’s still warm 2,4-D will work well, but you will get better thistle control by using a little less 2,4-D and adding a small amount of Banvel or other dicamba product to the mix. Herbicides to help control thistles in pastures include Redeem, Ally, Curtail. When using any of these herbicides, read and follow label instructions, and be sure to spray on time. Next year, avoid overgrazing these pastures so stands thicken and can better compete with thistles. Now is a great time to go after those winter annuals and thistles. Last but certainly not least I want to point out several upcoming programs that you my want to attend if at all possible. If you are interested in any of these programs please contact the # provided, or our office and we will get the info to you. “Ag at the Crossroads Conference” – Agriculture and the Environment, Animal Welfare, Social Media; Thurs., Nov. 5, at Lancaster Events Center in Lincoln for info contact the Nebraska Ag-Relations Council @ 402-472-2821 “Nebraska Wind Power 2009 Conference” - Mon., Tues, Nov. 9-10th , at the Holiday Inn Conv. Center in Kearney for registration and information contact: Terri Donahue at Nebraska Farmers Union - 402-476-8815 “2009 Beef Producer Roundup Tour” – Wed - Thurs, December 2nd & 3rd: Meet the bus at 8 am, North Platte; 9 am at KRVN in Lexington; 10:00 am Kearney at NE Beef Council Office on 2nd. Call Ne Beef Council - 800-421-5326 “The Pulse of the Ag and General Economy" - Featuring Dr. David Kohl of Va Tech, Farmers/Ranchers College, Wed., Dec. 2, at the Opera House in Bruning. Call Fillmore UNL Ext. at 402-759-3712 The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu