Submitted to: Washington State Weed Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 1, 1995
Publication Date: N/A
Interpretive Summary: Weed control in potato production is highly dependent upon herbicides. Environmental concerns, herbicide resistant weeds, the cost of pesticides, and loss of pesticides have led to research on developing alternative methods of weed control. A system has been developed that controls weeds in potatoes with 66% less herbicide than a typical broadcast herbicide application. Weeds are suppressed early in the season between the crop rows using a fall-planted green manure crop of rye or rapeseed. Later emerging weeds are controlled by a cultivation. Weeds in the crop row are controlled with a banded application of herbicide treating only 33% of the total area. Weed control and potato yield and quality using this system has been equal to that using a standard broadcast herbicide application. Another benefit of this integrated system is nematode suppression.
Technical Abstract: Prior to herbicide development for potatoes in the 1950's and 60's, weeds were controlled by mechanical cultivation, crop rotation, and other cultural practices. Once selective herbicides were developed for potatoes, they replaced cultivation as the primary tool used for weed control, weed control improved, and potato yield increased. Currently, most potato growers use a variety of chemical and nonchemical methods to control weeds in potatoes and other crops. Some nonchemical methods currently in use are crop rotation, proper seed size and quality, proper planting date and seeding rate, competitive cultivars, proper fertilization and irrigation, disease and insect management, cultivation, handweeding, weed surveys and monitoring, use of green manure crops, and control of weeds in fence rows and field margins. Cultivation has been shown to cause loss of soil moisture, spread pathogens, increase soil erosion, increase soil compaction, and injure roots and shoots of potatoes. The general recommendation is to keep cultivation to a minimum in potatoes. Yield loss due to cultivation in the absence of weeds ranges from 2 to 10%. Cultivation is also slow, often requires repeat applications, and increases fuel and equipment costs. Use of fall-planted green manure crops has received attention recently for nematode and weed suppression. Sudangrass and rapeseed have been used successfully as green manure crops to suppress nematodes in potatoes. Decaying residues of sudangrass, rapeseed, white mustard, and winter rye release allelopathic compounds, which can inhibit the growth of weeds. An integrated approach to weed management in potatoes should involve as many of the above methods as is feasible, economical, and effective.