Agronomy and Horticulture Department


Date of this Version



Insect Science, Plant Disease, & Weed Science, University of Nebraska Cooperative Extension, Institute of Agriculture and Natural Resources 87(12) (June 5, 1987)


Copyright 1987 University of Nebraska


In This Issue:

  • Control Perennial Weeds on ACR Acres
  • Poast Cleared For Use on Dry Edible Beans
  • Postemergence Weed Control in Soybeans
  • Poison Hemlock

Control Perennial Weeds

on ACR Acres Ideal growing conditions coupled with no tillage on ACR acres has set the stage for excellent control of perennial weeds. Keys to success in perennial weed control with herbicides are good growing conditions and correct growth stage of the weed.

Flower bud through flowering stages are ideal for treatment of perennial weeds with 2,4-D, Banvel, and Roundup. Canada thistle, field bindweed, hemp dogbane, and common milkweed on undisturbed sites are at or approaching these growth stages. Swamp smartweed will be later in reaching treatment stage. ACR acres are an opportunity to deal with these weeds without a crop involved.

Poast Cleared For Use on Dry Edible Beans

The Environmental Protection Agency has granted Nebraska a specific exemption under the provisions of Section 18 to use Poast for the control of wild proso millet and volunteer corn in dry edible beans. Poast can be applied at a maximum rate of 1 1/2 pints per acre and may be applied twice during the growing season. The total amount of Poast applied during the growing season should not exceed 2 2/3 pints per acre. Applications of Poast should be made at least 60 days before harvest. Wild proso millet and volunteer corn should be treated when they are between 4 to 10 and 6 to 20 inches tall, respectively. Fieldbeans at all stages of growth are tolerant to Poast. Poast can be applied by air or ground in a minimum of 5 gallons of water per acre. A permit system will be in effect for the use of Poast on dry edible beans and, therefore, the grower should contact his local pesticide dealer for the appropriate permit.

Postemergence Weed Control in Soybeans

Timing of postemergence herbicide applications is more dependent on the weed growth stage than crop stage. However, small weeds are more readily controlled than large ones. Basagran, Blazer, Tackle, combinations of these, Classic, and Cobra should be used when most susceptible weeds are no taller than 4 inches for best control. Nitrogen solutions (28-0-0 and 32-0-0 at 1 gallon per acre) increase Basagran and Blazer activity but weed size limitations remain. Taller weeds are defoliated but they often recover.

Poison Hemlock

Poison hemlock is widely distributed throughout Nebraska and much of the rest of the world. It is a biennial which reproduces by seed only. The plant has large fern-like leaves and grows to a height of 5 to 6 feet during the second year. The plant produces large showy umbels of many white flowers in late May, June, and July. The stems are hollow with purple blotches. The plant g rows in wet wasteland along streams, gardens, and roadsides.