Over the past week, I've been working on getting the weeds and grass controlled around my pecan trees (photo at right). It is widely accepted that total vegetative control around young trees is one of the key factors in promoting rapid tree growth and greater nut production. There are several ways to achieve weed control around pecan trees including tillage, herbicides, and hardwood chip mulch. But in my orchard, I've opted for spraying herbicides.
When I first started working with pecans back in the early 1980's,
glyphosate (Roundup) was the easy choice for total vegetation control. All you needed to do was to make sure you didn't hit pecan leaves or green bark with the spray. However, once roundup ready crops were developed, the widespread use of glyphosate has led to the proliferation of roundup resistant weeds.
This year, I have used a combination of herbicides around my trees. I used Gramoxone (a plant desiccant) to control existing winter annual weeds, and Simazine (a pre-emergent herbicide) to control germinating weeds and grasses. Later this summer, I'll come back with a broad spectrum contract herbicide to address any additional weed problems. I'll rotate between
glufosinate ammonium (Rely) and glyphosate (Roundup) to help avoid resistance issues.
In my orchard, most of my trees started out as volunteer seedlings. So for these trees I drive a utility vehicle from tree to tree carrying a 25 gallon sprayer in the back (photo at left). I try to create a 6 to 7 foot weed-free zone around each tree. I do not try to drive and spray at the same time. At each tree, I stop and get out so I can spray around each tree being very careful not to get any spray drift on the tree.
Minimizing spray drift is very important when spraying around young trees. Last fall, I planted some one-year-old seedlings in some of the gaps in my volunteer orchard. I caged these trees to ward off the deer and carefully sprayed around the seedling (photo at right). When spraying near the small tree, I always ease up on the water pressure coming out of the nozzle. This dramatically cuts down the creation of a fine spray mist that can drift onto the green bark of the seedling.
Vegetation control is not so critical for the performance of mature pecan trees. The oldest trees on my farm are in the pecan breeding block which is planted in rows. Here, I spray a herbicide strip down the row using a simple one-nozzle boom sprayer mounted on my tractor. The herbicide strip has two functions. First, it serves to control climbing weeds such as poison ivy, trumpet vine, and wild grape. And second, it makes mowing the ground cover much easier. I can mow in one direction without having to try to weave in and out of the trees. In the volunteer orchard, I mow in two directions to get all the ground cover mowed. This means I'm covering the same ground twice every time I mow.
