Perennial Broadleaf Weed Control
Perennial broadleaf weeds such as horsenettle, common milkweed, hemp dogbane, bigroot morningglory, trumpetcreeper, and maypop passionflower are normally more prevalent in reduced tillage and no-till systems than in conventional tillage systems. Except for the control obtained with Roundup applied at planting in no- till systems, perennial broadleaf weeds cannot be controlled in soybeans. The only way to control these weeds is to plant corn in rotation with soybeans and follow an effective management program in corn.
To control these weeds in corn, make a lay-by application of 1 pint per acre of 2,4-D amine with a surfactant when the corn is 15 to 20 inches tall. After corn harvest and before frost, re-treat infested areas with a mixture of 1 pint 2,4-D amine plus 1/2 pint Banvel per acre with a surfactant. Alternatively, apply 4 quarts of Roundup per acre or use a 2 percent solution of Roundup for spot treatment. Fall tillage is also helpful in reducing the buildup and spread of these perennial weeds.
In addition to the options listed above, curly dock can be controlled with a preplant application of Harmony Extra. Apply 0.5 ounce per acre of Harmony Extra to emerged curly dock. The Harmony Label specifies application at least 45 days before planting soybeans.