\m 9 3 29 2 1 'Successful Weed Control in Small Grains' \m 99 46 39 4 1 'Herbicide Recommendations for Use in Small Grains' \t'January 1988' 'IX-'page \a Danny Colvin, Extension Weed Specialist \a \a WEED CONTROL IN SMALL GRAINS Danny Colvin, Extension Weed Specialist \h 1 'Successful Weed Control in Small Grains' WEED CONTROL IN SMALL GRAINS Successful Weed Control in Small Grains Successful weed control in small grains involves using good management practices in all phases of small grain production. In Florida, winter weeds compete with small grains for moisture, nutrients and light with the greatest amount of competition occurring during the first six to eight weeks after planting. In addition to the competitiveness of weeds, those left to grow unchecked may cause harvest problems the following spring when the small grain is mature and ready to be gathered. CROP COMPETITION is one of the most important, but often one of the most overlooked tools in weed control. A good small grain stand which emerges rapidly and shades the soil surface is helpful in reducing weed competition. This involves good management practices such as: 1) deep tillage with either a chisel or turning plow instead of normal disk harrowing, 2) selection of the best suited varieties for your production area and seeded at a rate of about 40 seeds per square foot (2 - 2 1/2 bu/A), 3) plant in narrow rows of about 4" as compared to 8" rows to shade the soil surface quicker, and 4) timely nitrogen, fungicide and irrigation applications if needed. Utilizing these good management practices is necessary for producing maximum small grain yields and is also an aid in weed control. The plant that emerges first and grows most rapidly is usually the plant that will have the competitive advantage; therefore, everything possible should be done to ensure that the small grain, not the weeds, has this competitive advantage. KNOW YOUR WEEDS and choose the herbicide that is effective for your specific weed problem. In Florida, small grains are infested with several species of winter weeds most of which can be controlled by the phenoxy type herbicides, namely 2,4-D. However, some species that inhabit Florida small grain fields may escape an application of 2,4-D. Wild radish (Raphanus raphanistrum) is one such species and is often confused with wild mustard (Brassica kaber) but proper identification is crucial for their control. Wild mustard occurs sparsely within the Florida small grain growing region and can easily be controlled with applications of 2,4-D. Wild radish (on the other hand) is ubiquitous throughout Florida and is not easily controlled with 2,4-D. Most producers refer to both species as "Wild Mustard", therefore, promulgating and compounding the identification problem. In many instances growers have applied 2,4-D in hopes of controlling what they thought was wild mustard but in fact turned out to be wild radish. Wild radish was misidentified by the grower and the degree of weed control given by 2,4-D applications was inadequate. It should be understood that 2,4-D does have activity on wild radish but the restriction of 2,4-D application tied to small grain size usually allows the wild radish to attain a size in which the plant can overcome 2,4-D effects. The confusion of wild mustard and wild radish is the most notable instance where a misidentification can cause substandard weed control in small grains. \bCHEMICAL CONTROL - Proper choice of herbicide and rate applied are extremely important for weed control in small grains. Postemergence herbicides combined with the previously discussed management practices are important for ensuring that the small grain crop has the initial competitive edge. Generally, herbicide applications made to small weeds are much more effective than when weeds have attained an appreciable size. The most widely used herbicide in small grains is 2,4-D. Small grains vary in their tolerance to 2,4-D depending upon the growth stage when the herbicide is applied and the particular crop planted. Generally wheat varieties are the most tolerant, barley is intermediate and oats are least tolerant to 2,4-D. Rye is intermediate between wheat and barley. As a general rule the least injury to the grain crop with the use of 2,4-D can be expected when it is appled from full tiller to just before jointing. Most herbicides labeled for weed control in small grains belong to or are similar to the organo-auxin herbicide group and do have some potential for off-target spray drift. Care should be taken to avoid spray drift to sensitive crops. Furthermore, the State of Florida has enacted restrictions and prohibitions on organo-auxin herbicides used within the state. Refer to "Weeds in the Sunshine" Fact Sheet WIS-101 for information concerning this rule. The herbicides suggested in this section are those that have performed well in IFAS research and are labeled for application to small grains. Read and follow all label instructions and precautions. Accurate sprayer calibration is extremely important since rates too low may not provide adequate weed control and rates too high may injure the crop. Herbicides, like any pesticide, should be handled with care. Store herbicides behind locked doors in the original containers with the label intact and separated from seed, fertilizers and other pesticides. Use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of products named and does not signify approval to the exclusion of others of suitable composition. \b\v \h 1 'Herbicide Recommendations for Use in Small Grains' \v \v \v Herbicide Recommendations for Use in Small Grains ------------------------------------------------------------------------------- Trade Name and Broadcast Rate Common Name and Broadcast Rate Per Per Acre of Commercial Product* Acre of Active Ingredient** ------------------------------------------------------------------------------- 2,4-D 2,4-D (0.25 - 1.0) Several brands (1/2 to 2 pts of 4 lb/gal amine formulation) REMARKS: For control of winter annual broadleaf weeds. Apply after small grain is 5-8" tall or has fully tillered but before jointing. In most years this occurs in February. Weed control will be best if temperatures are 60 F or greater at application. Do not graze treated areas or harvest for dairy cattle feed within 2 weeks after treatment. Only amine or low-volatile ester formulations are legal for application in Florida. 3 + 3 Brominal (2/3 to 1 1/3 pt) bromoxynil (0.25 to 0.5) or 2 + 2 Bronate 4EC (1 to 2 pt) + MCPA (0.25 to 0.5) REMARKS: For control of wild radish and many other broadleaf weeds. Both products are mixtures of bromoxynil and MCPA and may give better control than bromoxynil alone. Apply after small grain has 3-4 leaves or is tillering and before weeds are past the 3-4 leaf stage. Do not apply to small grains during or after boot stage. Do not graze treated fields for 30 days after application. Banvel (1/4 pt) dicamba (0.125) or Banvel II (1/2 pt) REMARKS: Controls many annual broadleaf weeds. Apply after winter dormancy but before grain begins to joint. Do not graze treated areas or harvest for dairy cattle feed prior to crop maturity. Yield reduction will occur when treatment is applied to jointing wheat. Banvel (1/4 pt) dicamba (0.125) + 2,4-D (1/2 pt) + 2,4-D (0.25) REMARKS: Combination controls a broader spectrum of weeds than dicamba or 2,4-D alone. Apply after winter dormancy before grain begins to joint. This combination may cause some crop injury. Do not graze treated areas or harvest for dairy feed prior to crop maturity. Hoelon 3EC (2 pt) diclofop-methyl (0.75) REMARKS: For postemergence control of annual ryegrass in wheat. For best results apply when ryegrass is in the 1-3 leaf stage and before wheat begins to joint. Thorough uniform spray coverage of ryegrass is essential. May be mixed with Brominal or Buctril for broadleaf control. Do not graze or harvest for forage. \p (cont'd) \b\pHerbicide Recommendations for Small Grains - cont'd \p------------------------------------------------------------------------------ \pTrade Name and Broadcast Rate Common Name and Broadcast Rate Per \pPer Acre of Commercial Product* Acre of Active Ingredient** \p------------------------------------------------------------------------------ ME4 Brominal (3/4 to 1 pt) bromoxynil (0.375-0.5) or Buctril 2EC (1.5 to 2 pt) REMARKS: For control of wild radish and many other broadleaf weeds. Apply after small grain emerges but before weeds are past the 3-4 leaf stage. Do not apply to small grain during or after boot stage. Do not graze treated fields for 30 days after application. ------------------------------------------------------------------------------- * See "Weeds in the Sunshine" Fact Sheet WIS-101 for State rules pertaining to application of Organo-Auxin herbicides in Florida. Use of trade names does not constitute a guarantee or warranty of products named and does not signify approval to the exclusion of similar products. Read and follow all label instructions and precautions when applying any pesticide.