David Dickens our UGA Warnell School of Forestry Outreach specialist sent a few reminders for weed control in planted pine stands. Please see these comments and the attached publications for each pine species.
For the Coastal Plain, first yr (and 2nd when landowners can afford it; but first yr is the most critical) herbaceous weed control (HWC) applications should be starting in the next week or so with most/all over the top HWC spraying done by 15 April. Once we get into the first week of May, it becomes harder to find the planted rows, herbaceous weeds are harder to control, and we start to get hot and dry. April and May are the two driest months of the first ½ of the year and the main two herbicides we use for HWC; Oust and Velpar, are soil active herbicides (Velpar also has foliar activity), and rain is needed to “activate” these herbicides and to wash the Velpar off the planted seedlings.
When using Arsenal (not recommended over longleaf or slash) or Oust+Velpar wait at least two months after planting before applying these over the top of longleaf, wait 1-1.5 months after planting for loblolly.
On former peanut fields or where lime was recently applied, test the surface 0-6′ soil for pH. If the pH>6.0-6.2 then do not use Oust or Oustar (for those that still have some.
The Piedmont herbaceous weeds growth tend to be 2+ weeks behind the Coastal Plain weeds, so over the top spraying should start the 3rd or 4th week of March and be done by early May. Higher doses of Oust+Velpar are needed for the more clayey Piedmont soils.
The general rule of thumb for broadleaf weeds is to spray when weeds are ankle to calf high, regardless of the latitude of the stand.
For More information on specific species and weed situations reach out to your county agent for help.