Hay Bales: It's weed control time

Mike Trammell Pottawatomie County Ag Educator & Multi-county Agronomist
Mike Trammell joined the team as the Pottawatomie County agriculture extension educator and multi-county agronomist.

Do you remember that pasture that was covered by yellow flowers last spring? Was it buttercups? How about that pasture that had curly dock or red sorrel and we told you to wait until fall or the following spring to spray? Did you have a pasture that was covered with thistles last spring and it went to seed? If so, it’s time for you to think about loading up the sprayer and taking care of the problem.

We have been blessed with some rains this fall and if you go out and check, many of the plants we consider as weeds come next spring will already have germinated, or if they are cool-season biennials or perennials, they have already started growing and can be readily found out in your pastures. Fall or early spring is the best time to control these cool-season annuals. When these plants become more mature in late spring and early summer, they will become more difficult to control and more costly.

Buttercups are easily recognized in early spring by their bright yellow flowers. They tend to emerge in the fall and overwinter as low growing plants that send up a stem and flower in late spring. They are extremely difficult to control when they are in the flowering stage and producers who have observed them in their pastures this past spring should consider a late fall herbicide application or a February or March herbicide application for control. These plants are a lot easier to control during these time periods. Herbicide applications that work well on buttercups include fall applications of Grazon P+D, Aminopyralids (do not spread manure from animals that have grazed aminopyralid treated pasture, or consumed forage or hay within 3 days of treatment on land used for growing broadleaf crops. Otherwise, urine and manure from may contain enough aminopyralid to cause injury to sensitive broadleaf plants), 2,4-D + Dicamba, Aminopyralid, Cimarron max, or Cimarron (only use the Cimarron products on pastures you do not expect grazing of ryegrass on, since these products may control the ryegrass seedlings.).

Red sorrel, smooth dock and curly dock are three cool season plants that are in the same family and are collectively called sour dock by producers in southeastern Oklahoma. These plants tend to be problems in moist pasture situations and are extremely difficult to control when they send up their stems in the spring. They tend to go unnoticed until seed head formation begins but by then, it is usually too late for chemical control. The best times to spray these plants are in October or November on a day when daytime temperatures are expected to be above 60 degrees. Herbicides that work well during these two time periods include 2,4-D, 2,4-D + Dicamba, Aminopyralid, Grazon P+D, GrazonNext HL, and Cimarron Max.

Thistles are also a cool season weed that can become problematic in spring pastures. There are several species of cool-season thistles that inhabit Oklahoma pastures with two of the worst being musk thistle and scotch thistle. These two thistles are considered noxious weeds and should be controlled when identified growing in a pasture. Most of the thistles that grow in Oklahoma pastures will emerge in the fall and overwinter in the rosette stage until late spring when they send up a stalk and initiate flowering and seed production. These weeds are easy to control prior to the formation of these stalks but become harder to control the closer they get to flowering. Herbicides that work well on thistles when they are in the rosette stage include 2,4-D, Grazon P+D, GrazonNext HL, Aminopyralids, Cimarron Max, and 2,4-D + Dicamba. The best times to spray these thistles is in October and November, when day daytime temperatures are expected to be above 60 degrees Fahrenheit.

Cool season broadleaf weeds by their nature tend to be easier to control when they are young and prior to seed head development. It is easy for these weeds to go unnoticed during the winter and early spring only to become a problem when they send up their reproductive stems and flowers later in the spring or early summer. Producers who have had problems in the past with these weeds should consider checking their pastures for these winter weeds in October and early November. If large populations are observed, plans should be made to treat these weeds in November or in March when the plants are easy to control. If you need assistance with weed identification or a chemical control recommendation that will fit your operation, we at extension can help.

If you have questions concerning this topic or related topics, please contact the OSU Extension Center at 273-7683, stop by the office, or visit our website: http://countyext.okstate.edu/pottawatomie/

The pesticide information presented in this publication was current with federal and state regulations at the time of printing. The user is responsible for determining that the intended use is consistent with the label of the product being used. Use pesticides safely. Read and follow label directions. The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.