Mimeo HO-32 January 1953 (2M)
Purdue University Agricultural Experiment Station
CHEMICAL WEED CONTROL IN VEGETABLES CROPS
G. F. Warren, J. E. Larsen, and N. K. Ellis
Department of Horticulture
Lafayette, Indiana
Chemical weed killers can be used to reduce the cost of weeding many vegetables and to save some crops when wet weather makes it impossible to cultivate. However, they must not be considered as a substitute for all hand weeding and cultivation, but rather should be used to supplement standard cultural practices.
There are many treatments in addition to those listed that may be valuable on certain farms. Only those that have rather wide adaptation are mentioned here.
Since weather and soil conditions greatly affect results, the best treatment for one location is not always the best in another. This information should, therefore, serve only as a general guide.
For all materials, the rates given are based on over-all coverage. It is often more economical to treat only a narrow strip over the row: in which case, the amount applied should be reduced according to the portion of the area treated.
Asparagus. On established beds, 2, 4-D at the rate of 2 pounds of acid equivalent per acre (4 pounds on muck soil) has given good control of most annual weeds.
The spray should be applied to the soil just after disking in the spring or at the end of the cutting season, but before spears appear. If annual grasses are a serious problem, 6 to 10 pounds of 90% sodium TCA may be added to the 2, 4-D spray. Small patches of perennial broadleaved weeds, such as Canada thistle and field bindweed, have been controlled with 2, 4-D during the harvest season by cutting all asparagus spears close to the ground just before spraying. Under favorable moisture conditions, granular calcium cyanamide has been used successfully to control small annual weeds in asparagus but this treatment has not been as widley adapted as the others mentioned here.
To control weeds in asparagus seedbeds, Stoddard solvent at 80 to 100 gallons or 2, 4-D at 1 pound of acid equivalent per acre have given good results as contact pre-emergence treatments.

Beans. A residual pre-emergence application of 6 to 8 pounds per acre of a dinitro compound or 15 to 20 pounds of sodium PCP will control most annual weeds in beans. On lima beans, when annual grasses are a problem, as high as 10 pounds of dinitro or 25 pounds of sodium PCP may be used. The application can be made any time after planting but before emergence of the beans.

Beets. An application of 8 to 12 pounds per acre of 90% sodium TCA applied at least 2 days before any beets emerge, has been widely used in the mid-west for control of annual grasses in beets.

Carrots, Celery. Dill. Parsnips. and Parsley. Stoddard solvent at 80 to 100 gallons per acre given good control of annual weeds in these crops. Apply as soon as most weeds have emerged but before any are over 2 inches high. Do not spray carrots or parsnips after the tap root is more than 1/4 inch in diameter to avoid any possibility of off-flavors. On celery use only in the seedbed. Stoddard solvent seems to give better weed kill when applied at night or on a cloudy day than when applied in the middle of a clear day.