General Information


D-638 is a special formulation containing 2,4-D acid. It is more effective than 2,4-D amines for controlling hard-to-kill weeds such as field bindweed, Russian knapweed, Canada thistle, leafy spurge, cattails, tules and nutgrass. D-638 should be applied when daytime temperatures are lower than 80 to 85 degrees. Spraying when temperatures are higher may cause rapid foliar burn and decrease the product’s effectiveness. Treatment at higher temperatures also increases the possibility of crop injury. INJURY TO CROPS FROM THIS HERBICIDE MAY OCCUR. IF YOU ARE NOT PREPARED TO ACCEPT SOME DEGREE OF CROP INJURY, DO NOT USE THIS PRODUCT. Crop varieties vary in response to 2,4-D and some are easily injured.

Apply D-638 only to varieties known to be tolerant to 2,4-D. If you are uncertain concerning tolerant varieties or local use situations that may affect crop tolerance to 2,4-D, consult your seed company or state Agricultural Extension Service for advice.

GENERAL RESTRICTIONS: Do not apply product through any type of irrigation system. Do not use in or near a greenhouse.

MIXING INSTRUCTIONS: Add one-half the required amount of water to the spray tank; then add D-638 with agitation, and finally, the balance of the water with continued agitation. Provide continuous agitation to insure uniform spray mixtures. Use spray mixture as soon as possible after mixing.

COMPATIBILITY: If D-638 is to be tank mixed with fertilizers or with other pesticides, compatibility should be tested prior to mixing. To test for compatibility, use a small container and mix a small amount (0.5 to 1 quart) of spray, combining all ingredients in the same ratio as the anticipated use. If any indications of physical incompatibility develop, do not use this mixture for spraying. Indications of incompatibility usually will appear within 5 to 15 minutes after mixing. Read and follow the label of each tank-mix product used for precautionary statements, directions for use, geographic and other restrictions.

COMBINATION WITH LIQUID NITROGEN FERTILIZER: Use the recommended amount of D-638 per acre for weeding and feeding corn, small grains, grasses for production or grass pastures as directed on the label. Use the fertilizer at rates recommended by supplier or Extension Service Specialist. Fill the spray tank about half full with the liquid fertilizer, then add D-638 with vigorous agitation, and complete filling the tank. Apply immediately and continue agitation in the spray tank during application. Do not allow mixture to stand overnight. NOTE: Fertilizers can increase foliage contact burn of herbicides. Reducing the fertilizer rate and concentration will reduce the hazard of leaf burn.

Susceptible Plants

Do not apply under circumstances where spray drift may occur to food, forage, or other plantings that might be damaged or crops thereof rendered unfit for sale, use or consumption. Susceptible crops include, but are not limited to cotton, okra, flowers, grapes (in growing stage), fruit trees (foliage), soybeans (vegetative stage), ornamentals, sunflowers, tomatoes, beans, and other vegetables, or tobacco. Small amounts of spray drift that might not be visible may injure susceptible broadleaf plants.


All aerial equipment and ground application equipment must be properly maintained and calibrated using appropriate carriers or surrogates.

For aerial equipment, the boom length must not exceed 75% of the wingspan or 90% of the rotor blade diameter.

Release spray at the lowest height consistent with efficacy and flight safety. Do not release spray at a height greater than 10 feet above the crop canopy unless a greater height is required for aircraft safety. This requirement does not apply to forestry or rights-of-way applications.

When applications are made in a crosswind, the swath will be displaced downwind. The applicator must compensate for this by adjusting the path of the aircraft upwind.

For ground boom application, do not apply with a nozzle height greater than 4 feet above the crop canopy.

Refer in the label regarding tank mix information.

Limitations, Restrictions, and Exceptions


WHEAT, OATS, RYE and BARLEY (not underseeded with legumes)


Apply 1-1/2 pints when grain is fully tillered and wild garlic or onion plants are small. Apply 2 pints after harvest in the crop stubble. For control of new fall growth of wild onion or garlic, refer to FALLOWLAND use directions.

Restrictions and limitations for use on cereal grains:

- For aerial application on grain, apply in 2 or more gallons of water per acre. For ground application, a minimum of 10-15 gallons of water per acre is recommended for proper spray coverage.

- Do not mix with oil for crop uses.

- Do not permit dairy animals or meat animals being finished for slaughter to forage treated grain fields within 2 weeks after treatment.

- Do not feed treated straw to livestock if a preharvest treatment or emergency treatment as described above is applied.

D-638 contains 0.35 pounds a.e. of 2,4-D per pint. When tank mixing with products that contain 2,4-D, do not exceed a combined total of 1.75 pounds of a.e. per acre per crop cycle.

Pre-Harvest Interval

14 days

Restricted Entry Interval

48 hours