EM 8737 • Revised October 1999 Preventing Phenoxy Damage to Grape Vineyards

E. Hellman and J. Fults

What are phenoxy This family of pesticides GrapevinesDATE. are ? includes many very effective highly sensitive broadleaf weed killers. They are Phenoxy herbicides include Grapevines and many ornamen- used on lawns, golf courses, rights- 2,4-D, MCPA, Crossbow, Banvel, tal plants are extremely sensitive to of-way, and agricultural fields. OF Garlon, Weed-B-Gone, and Brush They are very popular for control- herbicides containing phenoxy- Killer. They also are the active type active ingredients. These ling blackberries and poison oak. ingredient (2,4-dichlorophenoxy- These products come in contain- plants are sensitive to phenoxy acetic acid, 2-methyl-4-chloro- herbicides throughout the growing ers ranging from 1-quartOUT bottles of phenoxyacetic acid, , or ready-to-use solution to 5-gallon season, but grapevines are most ) in “weed and feed” and vulnerable from the early growing drums of highly concentrated brush control products for use in active ingredient.IS They do not season through the bloom period the home landscape. (early April to mid-July). require a pesticide license for During the active shoot growth purchase and are readily available from department stores, home period, phenoxy damage often causes growth to stop temporarily improvement stores, co-ops, retail nurseries, farm chemical dealers, and to be retarded for several weeks. If the effects are not too etc. information:severe, normal growth will resume the same or following year. Severely injured vines may not recover for 2 years or more. Flower clusters are particularly sensitive; exposure during bloom can greatly reduce fruit set. Injured current vines also may have delayed fruit PUBLICATION ripening. Severe injury can prevent complete maturation of the fruit. The delayed maturation effect may exist in a vine for 1 to 3 years most before normal ripening resumes. THIS Slight injury may have little or no effect upon fruit maturity. Figure 1.—NewFor leaves and Figure 2.—Farther down the shoot, leaves growing tips show the most have a fan-shape appearance. Leaves severe damage. Affectedhttp://extension.oregonstate.edu/catalog leaves sometimes are cupped, and margins often are small, narrow, and mis- end in sharp points. shapen. Edward Hellman, Extension agent, North Willamette Research and Extension Center, Oregon State University; and Janet Fults, Oregon Department of . Oregon are small, narrow, and If you need to use a phenoxy vineyards have misshapen, and have herbicide, decrease the risk of experienced closely packed, volatilization by using an amine significant crop thick veins that (dimethylamine salt) formulation loss and long-term lack chlorophyll. instead of an ester formulation. damage to vines Farther down the Consider making applications in inadvertently exposed to shoot, damage early spring before grapevines phenoxy herbicides applied symptoms are begin to grow or in the fall after to distant targets. In contrast, progressively less their leaves have dropped. minor symptoms on grape severe; leaves have a Always use extreme caution leaves probably do not cause distinctive fan-shape when making applications when crop loss, but it can take signifi- appearance with desirable vegetation is present and cant time and energy to resolve parallel, strap-like, temperatures start warming up. the issue with a neighbor. clear veins (Figure 2). Monitor wind speed and direction The leaves sometimes are closely. Read and follow all label How damage occurs cupped, and the leaf margins directionsDATE. and precautions before Unintended drift of herbicides often terminate in sharp points. using any pesticide. Adding a can be caused by wind, shifting air Small, puckered, interveinal spots spray-thickening agent (drift currents, climatic inversions, or retain some green chlorophyll. OFretardant) may reduce spray drift, spraying at high pressure (which Damaged flower clusters set very although recent evidence suggests causes a very fine mist). Even small few or no berries. some drift retardants may break up amounts carried by the wind can or lose their chemical integrity create symptoms in grapevines. Reducing the risk when agitated or repeatedly Grapevines, caneberries, or other of phenoxy damageOUT passed through a spray pump. sensitive vegetation in close Be a good neighbor and don’t Consider using a herbicide with trespass with your chemicals, proximity to a sprayed area are at a different active ISingredient, such highest risk. However, even either directly by spray drift or as (Roundup), when indirectly through vapor drift. grapevines some distance from a you are trying to control difficult phenoxy-treated area can be Either way, as the applicator who weeds such as blackberry or decides to spray a product, you damaged under certain conditions. poison oak. Fall applications of Even slight winds can carry small will be held responsible for dam- glyphosate tend to be more effec- age, even if it is unintentional. spray droplets toward a vineyard. tive than spring applications. Temperatures above 70–75°F allow information: ester formulations of phenoxy herbicides to volatilize (vaporize) and be carried by the wind, even For more information several days after the spray appli- Additional copies of this publication are available from Willamette cation. Valley and Metro county offices of the Oregon State University Exten- currentsion Service. Symptoms PUBLICATIONThis publication, our Publications and Videos catalog, and many of phenoxy injury other educational materials and information resources are available on The symptoms of phenoxy the World Wide Web at: herbicide damage are most dra- eesc.orst.edu (Extension and Experiment Station Communications) matic on the youngestmost leaves and theTHIS tips of growing shoots osu.orst.edu/dept/infonet/ (Northwest Berry & Grape Information Net) (Figures 1 and 2). Affected leaves For

© 1999 Oregon State University. This publication may be photocopied or reprinted in its entirety for noncommercial purposes.http://extension.oregonstate.edu/catalog This publication was produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Exten- sion work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities, and materials-without regard to race, color, religion, sex, sexual orientation, national origin, age, marital status, disability, and disabled veteran or Vietnam-era veteran status-as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. Oregon State University Extension Service is an Equal Opportunity Employer. Published July 1999. Revised October 1999.