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


- Apply to actively growing annual broadleaf weeds. Use 2/3 to 1-1/3 pints when weeds are small; use higher rates on older weeds. Do not apply to young grasses with fewer than 6 leaves or prior to tillering, as excessive injury may result. Do not apply more than 1-1/3 pints until grasses are well established as excessive injury may result.

- Beggarticks, common broomweed, knotweed, mallow (venice or little), musk thistle, prickly lettuce, Russian thistle, salsify (western or common), smartweeds (annual species), vervains, : These species may require repeat applications and/or use of higher rate recommended on this product label even under ideal conditions for application.

- Pigweeds (Amaranthus spp.): Control of pigweeds in the High Plains area of Texas and Oklahoma may not be satisfactory with this product.

Restrictions and limitations for use on Conservation Reserve Program areas:

- Use at least 2 gallons of water per acre by air and 5 gallons of water per acre by ground.

- Do not harvest or graze treated Conservation Reserve Program areas.

- Do not apply to grasses in the boot to dough stage if grass seed production is desired.

Restricted Entry Interval

48 hours