Thursday, May 15, 2014

Controlling weeds around young pecan trees

   During most years, regular spring rains and muddy soil conditions keeps us out of the field at this time of year. In fact, the vast majority of floods that occur on the Neosho River happen during the months of May and June. However, a drier than normal Spring has enabled us to get an early jump on weed control this year. During periods of calm winds, we use a 30-gallon, electric sprayer to apply roundup in a seven foot circle around each tree (photo at right).
   Roundup (gyphosate) is a systemic, contact herbicide that can damage pecan trees if spray droplets contact any green tissue. To limit possible spray drift problems, we use a hand held spray wand and adjust the nozzle to a course spray pattern (large droplet size). We use a generic form of roundup at the rate of 2 oz. per gallon. To help the roundup penetrate weed leaves, we add liquid ammonium sulfate and a non-ionic surfactant to the spray tank.

    What you don't see in the photo above is the fact that we walk through the orchard a week before spraying and trim off any basal sprouts or any new shoots sprouting from the lower portion of the trunk. One of the most common causes of roundup injury to young pecans is accidentally hitting unseen basal sprouts hidden in tall weeds.
    During this preliminary walk through the orchard, we discovered several trees that were killed back to the ground by mid-winter cold. In the photo at left, you can see we had two years of strong growth on this young graft but the entire tree died back to the ground line following last winter's intense cold.  However, all is not lost. This tree has already developed a couple of basal sprouts that will provide a new place to graft in the future.
    In the mean time, we were fortunate to discover these new shoots before applying our herbicide spray. First, we pulled the weeds away from the stump sprouts by hand. Then, we very carefully sprayed the rest of the area around the tree. Roundup can penetrate both the leaves and green bark of tender pecan shoots, so be very careful.