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


- To control dandelion, plantain and most other common broadleaf weeds in turf, apply in spring or fall when these weeds are growing actively. Treat wild garlic or onion in three successive seasons (example: spring, fall, spring).

- Beggarticks, common broomweed, knotweed, mallow (venice or little), musk thistle, prickly lettuce, Russian thistle, salsify (western or common), smartweeds (annual species),vervains, 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.

- 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 ornamental turf areas:

- A minimum application volume of 25 gallons per acre is recommended for use on turf.

- Do not apply to newly seeded areas until sod is formed and grass has been cut a few times. Do not use 638 for susceptible southern grasses such as St. Augustine. Bentgrass and clover may be injured by this treatment.

- Do not apply more than 2 broadcast applications per year per treatment site. This does not exclude spot treatment.

- Do not allow people (other than applicator) or pets on treatment area during application.

- Do not enter treatment areas until sprays have dried.

Restricted Entry Interval

48 hours