Weed Control in Small Grains

Although weeds are usually less of a problem in small grains than in row crops, heavy infestations of annual weeds, quackgrass, or wild garlic reduce grain yields and/or quality

Good cultural practices will result in a thick, heavy stand of small grains that will compete effectively with weeds during the early stages of crop development. Crop rotation, sound soil management practices, the use of certified seed of recommended varieties, proper seedbed preparation, and timely planting all contribute to weed control in small grains. Herbicides can be used to supplement these cultural practices as needed (Table 5.9.1)

Small grain fields should be checked for weeds in the fall (for winter wheat or barley) or early spring because most herbicide applications should be made prior to jointing (Growth Stage 6), or the appearance of the first node at the base of the plant (usually 4 to 8 inches tall with 12 or more leaves). Herbicide application during grain ripening may aid harvest operations but will not increase grain yields.

Many winter annual broadleaf weeds in winter wheat can be controlled with spring applications of 2,4-D or Banvel/Clarity. Both can cause crop injury if used at growth stages other than those recommended. In addition, Banvel/Clarity may delay wheat maturity when used according to guidelines.

Spring applications of 2,4-D or Banvel/Clarity are not effective against corn chamomile. Buctril is effective on corn chamomile when the rosettes (clusters of leaves in circular form) are less than 1 inch across. Corn chamomile usually reaches this stage within a month after seeding so Buctril applications for this weed should be made in the fall. Other annual weeds controlled with Buctril are field pennycress, field pepperweed, shepherdspurse, small seed falseflax, wild mustard, wild radish, and yellow rocket. Harmony Extra is a better choice for corn chamomile control than Buctril if application is delayed until spring.

Herbicide Resistance Management

Herbicide resistance management involves the use of crop rotation along with herbicide rotation and/or use of herbicide combinations that include herbicides with different sites of action (how they affect weeds). These practices will help manage existing herbicide resistant weed populations and delay development of new resistant weed populations.

To effectively utilize herbicides with different sites of action, everyone involved in decisions about weed management must have site of action classification readily available. The Weed Science Society of America (WSSA) has approved a numbering system to classify herbicides by their site of action (Mallory-Smith, C.A. and Retzinger, E.J. 2003. Revised classification of herbicides by site of action for weed resistance management strategies. Weed Technol. 17:605-619).

Table 5.9.1

Chemical weed control in small grains
Weed SituationAmount of Product(s) per AcreRemarks and Limitations
Oats (not seeded)
Annual broadleaf weeds1/2-1 pt. of 3.8 lb./gal. 2,4-D amine salt formulation 1Group 4 Herbicide: Apply postemergence at growth stage 4 or 5 as shown in Fig. 5.4.1 (usually 4-8 in. tall). Do not spray oats in the boot or dough stage.
Wheat or barley (not seeded)
Broadleaf weeds1/2-1 pt. of 3.8 lb./gal. 2,4-D amine salt formulation 1Group 4 Herbicide: Apply postemergence in the spring at growth stage 4 or 5 as shown in Fig. 5.4.1 (usually 4-8 in. tall). Do not spray small grains in the boot or dough stage.
4 fl. oz. Banvel or 4 fl. oz. ClarityGroup 4 Herbicide: For winter wheat, apply postemergence in the spring at growth stage 4 or 5 as shown in Fig. 5.4.1 (usually 4-8 in. tall). Time of application is critical. May delay wheat maturity. Use 3 fl. oz. for spring barley, before the 4-leaf stage.
Wild garlic1.5 pt. of 3.8 lb./gal. 2,4-D ester formulation 1Group 4 Herbicide: Apply in the spring when grain is fully tillered (at growth stage 4 or 5 as shown in Fig. 5.4.1) but before elongation or jointing of the stems occurs (growth stage 6). Do not spray small grains in the boot to dough stage.
Wild garlic and winter annual broadleaf weeds including corn chamomile0.75-0.9 oz. Harmony ExtraGroup 2 Herbicides: Add a nonionic surfactant to the spray solution and apply when wild garlic plants are less than 12 in. tall with 2 to 4 in. of new growth. Does not control wild onion.
Corn chamomile and other winter annual broadleaf weeds1.5 pt. of 2 lb./gal. BuctrilGroup 6 Herbicide: Apply to emerged chamomile in fall when rosettes are less than 1 in. across.
0.45 – 0.9 oz. Harmony ExtraGroup 2 Herbicide: Apply to young, actively growing weeds in fall after wheat is in the 2-leaf stage or in spring before the flag leaf is visible (growth stage 8 as shown in Fig. 5.4.1). Add a nonionic surfactant to the spray solution.
Fall-Sown of Winter Wheat only (not seeded)
Roughstalk bluegrass and Cheat4.75 oz. *§OspreyGroup 2 Herbicides: Special Local Needs registration in NYS. A copy of the Special Local Need label must be in applicator’s possession at the time of application. Add a nonionic surfactant plus ammonium nitrogen fertilizer or a methylated seed oil or a “basic blend” type adjuvant to spray solution according to label. Applications may be made from wheat emergence up to the jointing stage of wheat (growth stage 5 as shown in figure 5.4.1). Limited research results suggest that spring applications are more effective than fall applications.
NOTE: If small grains are seeded with a legume, see Table 4.11.1 for weed control guidelines.
1For other 2,4-D formulations, use Table 7.2 to calculate the amount of herbicide needed per acre.

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