Weeds are a problem year after year even where they have been diligently controlled. A major reason for this is that weed seeds continually move into fields by irrigation water, wind, equipment, contaminated seed and other means. Controlling weeds on irrigation ditch banks can greatly help to reduce weed seed movement into fields.
The EPA regards non-crop areas as those that are not dedicated to crop production. Although crops are not normally grown on irrigation ditch banks, these areas should not be managed as non-crop. Several very broad spectrum and long lasting herbicides are registered for non-crop areas which include roadsides, industrial sites, fence rows, around structures, railroads etc.. Irrigation ditch banks should be considered separately because of their proximity to crop fields and irrigation water and the potential for herbicide movement into sensitive areas.
It is important to read the label carefully and only use those products that are specifically allowed for use on ditch banks. Some products are restricted to drainage ditch banks or dry ditches. Some can be used only above the water line and some can only be used for non-irrigation ditch banks Because most ditches here are used for irrigation, this can be confusing. The definition of a ditch however, can include an open trench or natural channel. It can also include ditches that are not in use for long periods of time. Some labels specify how long this non-use period should be. Some herbicides that have been used on ditch banks in the past are now restricted from this use because of groundwater contamination or off target movement that has occasionally occurred. Do not assume that products that were used for ditch banks in the past can still be used. Even very old products like MSMA can no longer be used for irrigation or drainage ditches. The following summarizes how some of the more common products that have been used on ditches can be used although the product labels should be read for more complete directions. There are several broad spectrum herbicides that are registered for “Non-Crop” sites but that are retricted from use on irrigation ditches. These include Bromacil,Triclopyr,Imazapyr,Thiazapyr Flumioxyzin,Imazomox,Topamezone,Valpar and others.