Agricultural pest management
Special Weed Problems
(Reviewed 4/13, updated 4/13)
Primary species that are difficult to control are the perennial grasses bermudagrass, johnsongrass, and dallisgrass. Control of these weed species before planting has been discussed under the preplant section. While it is best to control (eradicate) them before planting, if after planting these weeds are still present, a program is needed for their management.
All three species are sensitive to glyphosate. To achieve the best control, cultivate the weeds where possible to chop the stems and rhizomes into small pieces. Then encourage regrowth by irrigating; this will produce a lot of new leaf area on the weeds. Before the weeds produce flowers or seeds, treat with glyphosate and spot-treat any regrowth that occurs.
It will be necessary to control seedlings of these grasses with preemergence materials or spot treatments of glyphosate or paraquat before they become established. Seeds of these species last at least 2 years in the soil, so frequent monitoring is necessary for continued control. Do not allow perennial plants to reestablish or set seed.
Two other species difficult to control are field bindweed and yellow nutsedge. Seedling bindweed or young nutsedge can be controlled by cultivating when the soil is dry. Established populations of field bindweed can be reduced by irrigating in summer to encourage vigorous growth, then treating with glyphosate at flowering. This is a nonselective treatment and will kill other weeds as well. Regrowth will also have to be treated. Yellow nutsedge can be reduced in a similar manner by re-treating with glyphosate before the nutsedge reaches the five-leaf stage so new tubers do not have the opportunity to form. To be effective, this treatment usually requires multiple applications during the season at intervals of 21 to 28 days apart. It may take two or more seasons of repeated timely treatments to eradicate yellow nutsedge.
Young kiwifruit vines can be injured by glyphosate. Protect green wood or the foliage of young vines by using:
UC IPM Pest Management Guidelines: Kiwifruit
K. J. Hembree, UC Cooperative Extension, Fresno County
Acknowledgment for contributions to Weeds:C. L. Elmore, Vegetable Crops Weed Science, UC Davis
W. T. Lanini, Plant Sciences, UC Davis