General Information


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. 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 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.


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

Limitations, Restrictions, and Exceptions


WHEAT and BARLEY (not underseeded with legumes)

Apply after grain is fully tillered (usually about 4-8 inches high) but not forming joints in the stem. Apply when weeds are near bud stage. Do not spray grain in boot to dough stage.

- Alfalfa, Austrian fieldcress, bindweed (hedge,field, European), Canada thistle, docks, dogbanes, goldenrod, ground ivy, hoary cress, many-flower aster, nettles (including stinging), orange hawkweed, tansy ragwort, vervains, western ironweed, wild garlic, wild onion : These species may require repeat applications and/or use of higher rate recommended on this product label even under ideal conditions for application.

- Use the lower rate if small annual and biennial weeds are the major problem. Use the higher rate if perennial weeds or annual and biennial weeds are present which are in the hard-to-kill categories as determined by local experience. The higher rates increase the risk of grain injury and should be used only where weed control problems justify the risk of grain damage. Do not apply to grain in the seedling stage.

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.

Restricted Entry Interval

48 hours