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


- Spray weeds in bud to bloom stage, or in good vegetative growth. Do not disturb treated area for at least 2 weeks after treatment, or until weed tops are dead, except as directed in the SPECIAL WEED PROBLEMS section of the label.

- 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.

Restrictions and limitations for use on fallowland and crop stubble:

- A minimum spray volume of 5 gallons per acre by air or 10-15 gallons per acre by ground is recommended.

- Do not plant treated fallow land until 3 months after treatment or until chemical has disappeared from soil.

- Do not graze dairy animals on treated areas within 7 days of treatment.

Restricted Entry Interval

48 hours