In orchard situations woody perennial weeds are very common and difficult to control. Preemergence herbicides have little or no activity on most woody perennial weeds and Gramoxone, Rely, and 2,4-D generally do not provide adequate control either. Touchdown and Roundup Ultra are only effective when application is appropriately timed. In general, woody perennials are most susceptible to Roundup or Touchdown near flowering or in late summer when the herbicide is most likely to be translocated to roots. However, this does vary from species to species and there are exceptions like English ivy and greenbrier. In the table below I listed four commonly found woody perennial weeds in orchards with application rate and time information. A more complete table with additional weed species is in the apple spray guide. Roundup and Touchdown labels are also very informative with application time and rate for controlling a number of perennial weeds.
There are several things to remember when controlling woody perennial weeds in the orchard.
Know the weed species you are trying to kill and determine the appropriate application time using the spray guide table or the product label. For identification assistance contact the cooperative extension service in your county.
Scout regularly. This may prevent missing the application widow for the species you want to control. Scouting can result in early detection of weed problems before they impact a large area in the orchard.
Remember woody perennial weeds are difficult to manage and it may take two or three years to clean up an area in the orchard.
A number of these species require applications in late summer and fall. Extreme caution must be taken around trees while using Roundup and Touchdown during late summer and fall or serious injury may occur.
% Solution of Roundup Ultra
(weed growth stage)
First Flowering through November
2 weeks either side of full bloom (early summer)
Late summer until first sign of fall color.
Full flower (Late summer)
1 % solution is equivalent to 1.25 ounces of herbicide per gallon of water