630.7 i£6c no.907 rw 1987 ;•: : UNIVERSITY OF ILUNOIS LIBRARY AT URBANA-CHAMPAIGN ACES UNIVERSITY OF ILLINOIS AGRICULTURE LIBRARY ^Weed Management Guide 1988 FOR COMMERCIAL VEGETABLE GROWERS The University of Illinois and its agents assume no responsibility for results from the use of herbicides, whether or not they were used in accordance with suggestions, recommendations, or directions of the manufacturer or any governmental agency. Weeds pose one of the most important threats to the income of vegetable growers in the United States, causing millions of dollars in losses as a result of lower yields, poorer quality, and reduced efficiency. Her- bicides are only part of a complete weed control program that should include mechanical control, mulches, crop rotation, and herbicides as needed. As you decide v/hich weed control methods and which labeled herbicides to use, take into account past weed infestations, the present crop, planned future qrop rotations, soil types, and pesticide prices. In some instances, a weed control program may include only mechanical control, but in other in- stances, herbicides will be required to supplement mechanical control. Use a cultivator or a sharp hoe to cut weeds off while breaking up the soil crust. Do not till too deeply, or shallow-rooted crops may be injured and a fresh supply of weed seeds may ger- minate. Plastic mulches, besides controlling weeds, will con- serve moisture and increase the soil temperature, which can improve early season crop growth. Only herbicides labeled for the crop should be used be- tween rows of mulch. Care should be used if a herbicide is applied under the mulch because crop injury can occur. Treflan, Prowl, Sonalan, and other herbicides that volatilize should not be applied under mulches or row covers. Crop rotation should also be considered an integral part of vegetable-crop weed control. By rotating fields among different families of crops (for example, be- tween muskmelon and soybeans), problems with dis- eases, insects, or weeds can sometimes be avoided. A wider spectrum of herbicides is generally available for use in agronomic crops, so weed problems that cannot be controlled in vegetable crops may be con- trolled in agronomic crops. You shourd scout your area to determine the existing weed problems, and if these weeds are difficult to control in planned future crops, you should consider other crops. Several herbicides are often labeled for a crop. The choice of which of these herbicides to use is yours. Scouting your area to determine which weeds are present will allow you to select the herbicide that will give you the best results. Tank mixes can be used to give broader spectrum control. Check the labels for the specific tank mixes that are allowed. All the herbicides labeled for a given crop are not necessarily listed below. Also, because revisions may change some herbicide uses, always read and follow carefully the directions on a current herbicide label before using any product. If you are unfamiliar with a herbicide, conduct a small evaluation under your environmental conditions and cultural practices be- fore using the herbicide extensively. Always Read and Understand the Herbicide Label Before Using the Product Reading the herbicide label carefully is the most profitable use of your time spent in weed control. Information on the label will direct you to the correct uses, application methods, and rates. Following label directions will result in the best possible control with minimal crop injury. The label contains restrictions on use and discusses environmental and soil conditions UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN COLLEGE OF AGRICULTURE COOPERATIVE EXTENSION SERVICE Prepared by J.B. Masiunas (revised annually) CIRCULAR 907 (September 1987) AUG that affect crop injury and influence the effectiveness of weed control. Do not use any herbicide unless the label states that it is cleared for your particular use and crop. The label also states whether the herbicide is a restricted-use or general-use pesticide. Restricted-use pesticide labels contain a statement that the products are restricted, and that only licensed applicators can buy them and supervise their application. At present the only restricted-use herbicides labeled for vege- table crops are Bladex and Gramoxone. Any person who uses a restricted-use herbicide must be licensed as a private or commercial applicator by the Illinois Department of Agriculture. Consult your county Ex- tension adviser for information about this program. The information in this circular is current as of the date of publication. Watch for notices of changes in the EPA registration of herbicides in the Illinois Vegetable Farmer's Letter or the Insect, Weed, and Plant Disease Survey Bulletin. Contact your county Extension adviser or Vegetable Crops Extension, University of Illinois, 1 103 W. Dorner Drive, Urbana, Illinois 61801, for subscription information. Growers with Several Vegetable Crops Growers with several vegetable crops in a small area should consider using a low-percentage granular herbicide. Check the herbicide label closely for rates and application techniques. Application must be uniform and accurate or crop injury can occur. Consult Table 1 for a herbicide that can be used on your crop. Be sure to follow the label directions that pertain to each crop on which the herbicide will be applied. Stale Seedbed Treatment Roundup, dalapon, or Gramoxone can be applied outside the normal growing season to control emerged weeds. Weeds should be growing actively and the application must be made before the crop has emerged. If you are applying Roundup to control perennial weeds, it is recommended that Roundup be applied before working the soil. Once Roundup has been applied, it must be allowed to translocate throughout the perennial weed for several days or incomplete control may result. Follow Roundup label directions carefully for the rates and timing of application. If perennial weeds are not a major problem, you can eliminate early flushes of weeds by preparing the soil 10 to 14 days before planting and then applying Roundup, dalapon, or Gramoxone to all weeds that emerge. Plant the crop with minimal reworking of the soil. Never apply Roundup or Gramoxone to an" emerged crop because severe crop injury or death will occur. Roundup and Gramoxone will control most annual broadleaf and grass weeds. Neither herbicide has any soil residual activity, so other weed control measures will be necessary during the growing season. Gram- oxone will also suppress perennials by killing their shoots, but it should not be expected to control regrowth of perennial weeds from rhizomes or other underground storage organs. Roundup is better for controlling perennials, because it will kill shoots and translocate to destroy underground parts. Roundup will only suppress some particularly hard-to-control perennials such as bindweed, hemp dogbane, and milkweed. To obtain control of these perennials, applications of high rates or repeat applications of glyphosate (within label guidelines), or mechanical removal may be necessary. How to Use This Circular There are four tables in this circular. First, use Table 1 to determine the herbicides that are labeled for use in your crop. If you are not certain of the herbicide name, both the common name and the trade names of all herbicides in this circular are listed in Table 4. Once you have determined which her- bicides are available and the weeds present, use Table 2 to determine which of the labeled herbicides will provide the best control. Then consult Table 3 for restrictions, precautions, and other considerations that may limit your use of a particular herbicide. These tables are not intended to replace careful reading of a current herbicide label. ALWAYS READ THE LABEL BEFORE APPLYING ANY PESTI- CIDE. Table 1. Herbicides Labeled for Use in Vegetable Crops -a c e Q. c V .-> XI E E rt 03 "3. u 2 O c O- ^ £ c -^ -S £ < < E 03 a. o oj £ = « o cC «j c £ J! A « £- ») r U - Ci- " c u X .3 C 60 9J C 03 03 -2 i. 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