weed science
BP-10-7
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • DEPARTMENT OF BOTANY AND PLANT PATHOLOGY LILLY HALL OF LIFE SCIENCES • WEST LAFAYETTE, INDIANA 47907
POSTEMERGENCE AND HARVEST AID HERBICIDES FOR SOYBEANS
T.T. Bauman, J. L. Williams, Jr., and T.N. Jordan, Extension Weed Specialists
Delayed and Cracking Stage
Dyanap
Ancrack
Premerge 3
Lasso+Premerge 3
Lasso+Dynap

Early Post
Norex
Tenoran
Basagran
Dyanap

Directed Post
Butoxone SB
Butyrac 200

Double Crop
Lorox+Paraquat
Sencor+Lasso+Paraquat

Harvest Aid
Paraquat

Weeds limit soybean yields probably more than any other single factor. A combination of cultural practices and the use of herbicides is needed to reduce weed infestation. Many farmers depend too much upon herbicides alone to control weeds and do not effectively use the combination approach. The cleanest soybean fields are generally those that are in a rotation system. If your soil permits rotating your crop, this should be a primary consideration. Plant your crop when you can expect fast germination and growth. Shade is a good weed control measure. In extremely weedy fields, cultivate close with rotary shields. Where weeds such as johnsongrass and cocklebur are a problem use competitive varieties.

Effective chemical control is largely dependent upon the weed populations of each field, the capabilities of the available herbicides to control these weeds, and the timing of applications. Instances exist each year where the stage of growth of the weeds and soybeans is such that effective use of postemergence herbicides is no longer effective. If this is the case, save your money and hope for another chance at a later stage of growth or resort to cultural practices to control these weeds.

POSTEMERGENCE HERBICIDES

Postemergence applications of herbicides are usually necessary to obtain maximum weed control in soybean fields. Timely application of postemergence herbicides is essential.
Most early postemergence treatments work best when weeds and grasses are less than 2 inches tall and will usually do a better job when the weather is warm.
For severe infestation of difficult-to-control broadleaf weeds such as jimsonweed, cockle-

Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.G. Diesslin, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30,1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, religion, color, sex or national origin.