Cranberries
Kim Patten
Revised November 5, 2008
Preplant weed control  All major weed problems can be prevented by starting with a clean field and avoiding reinfestation. For proper preplant management, growers should consider spraying perennial weeds with several applications of an appropriate systemic herbicide, using sand free of weed seeds, fumigating soil, planting weed-free vines, cleaning equipment when moving between beds, and seeding dikes with cover crops effective in preventing weed infestation (e.g., dwarf perennial ryegrasses and some creeping fescues). 
Year-round weed management in bogs  Successful weed management in cranberries requires a comprehensive, year-round approach that alternates a combination of weed control practices over several years. Developing these strategies requires knowledge of each weed and weed control practice. First, identify weeds and gather information about the effectiveness of each weed control practice. Consider costs and select herbicide combinations that may be applied together or in split applications that control most weeds in the beds. Note each herbicide’s action within the plant. Then combine and alternate these products and other weed control practices to reduce the chance of developing resistant species or biotypes. Map the precise locations of different weeds in the bed to allow for spot application of herbicides. Removing weeds (especially perennial weeds) by hand is often necessary and should be done regularly. Mow dikes and other areas surrounding the beds periodically to prevent weeds from spreading or reproducing by seed. Shape dikes to accommodate mowing equipment. 
Applying herbicides  Herbicides must be applied at the correct rate and time to control weed growth with minimal chance for injuring the cranberries. Recalibrate your herbicide applicator every year. For spot applications make sure that your tank-mix is based on spray volume. Follow guidelines in this handbook on backpack sprayer calibration. Results will be more consistent if you read the herbicide label and other information about the proper application and timing of each herbicide. Rates suggested in this guide are stated as pounds of active ingredient per acre (lb ai/A) or pounds of acid equivalent per acre (lb ae/A). Numerous products with the same active ingredient are labeled for cranberries. These products may have different concentrations of active ingredient. To avoid rate problems, be sure cranberry is on the label and follow the rate listed on the label. Avoid applying herbicides when water is standing on the soil surface. To minimize phytotoxicity and improve weed control, apply herbicides to dry vines and water them in after application. At the beginning of each season, check with your Extension agent to see whether a Section 18 has been granted for a new herbicide. 
Warning  Using 2,4-D or similar materials on horticultural farms involves risk not only to the crop to which it is applied but also to crops in nearby fields. In some instances, however, careful use of 2,4-D enhances weed control with minimal chance for crop injury. Be careful to clean all 2,4-D from your equipment or to use separate sprayers before applying another product to other horticultural crops. Never use a volatile formulation of 2,4-D or similar material. Buy only a product that lists the intended crop on the label. 
CRANBERRIES—New Plantings
•  clopyralid (Stinger)
Rate  0.1 to 0.25 lb ai/A (0.25 to 0.66 pint/A)
Time  Apply only when cranberries are not actively growing. In new plantings, this begins when cranberry vines go dormant in late fall and ends with bud break.
Remarks  Newly growing vines are sensitive to Stinger. Identify susceptible weed species (legume and composite families), and apply postemergence when weed canopy becomes visible. Do not add surfactant or crop oil. Special local needs labels WA-030006 and OR-030009.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  mesotrione (Callisto)
Rate  0.33 to 0.67 lb ai/A (4 to 8 oz/A)
Time  Apply only after budbreak, but less than 45 days prior to flooding.
Remarks  Use a surfactant or crop oil as recommended by the label. 
Caution  Avoid using crop oils that injure cranberry vines. Do not exceed 16 fl oz/A or two applications per year. Allow at least 14 days between treatments.
Site of action  Group 28:  inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)
Chemical family  Triketone
•  napropamide (Devrinol 10G, Devrinol 50DF)
Rate   3 lb ai/A (30 lb/A Devrinol 10G), (6 lb Devrinol 50DF)
Time  Apply to weed-free soil surface after planting.
Remarks  Use lower rate on sandy soils. Requires irrigation or rain to activate. Results are best when applied just before weed seeds germinate.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide 
•  norflurazon (Evital)
Rate  1 to 1.5 lb ai/A (20 to 30 lb/A product)
Time  Apply after newly planted vines have rooted but  preferably in late winter or early spring, before weed growth begins.
Remarks  1 to 1.5 lb ai/A have performed adequately on new beds with low organic matter and high sand; 2.5 lb ai/A are required for new beds with high organic content.
Caution  Do not exceed 2.5 lb ai/A total on new beds in 1 yr. Hybrid varieties such as ‘Stevens’ and ‘Pilgrim’ are more prone to injury than ‘McFarlin’. Injury is likely in areas where water puddles. Some growers and researchers report reduced crop yields, especially with hybrids, when the product is applied in consecutive years. Use lower rates and alternate with other herbicides as soon as labels permit. 
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  Pyridazinone
•  clethodim (numerous product names)
Rate  0.94 to 0.125 lb ai/A (6 to 8 oz of 2 EC formulation)
Time  Apply to actively growing grasses, including annual bluegrass, at growth stage listed on label, using 0.5 to 1% nonphytotoxic crop oil or 0.25% nonionic surfactant.
Remarks  Carefully read label about adjuvants, effects of rain within 1 hr, application of other pesticides, and cultivation.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
•  sethoxydim (Poast)
Rate  Spray—0.28 to 0.47 lb ai/A (1.5 to 2.5 pints/A product). Spot treat—2 oz or 4 Tbsp/gal water + 2.5 oz or 4 Tbsp crop oil concentrate
Time  Apply at optimum growth stage listed on the label.
Remarks  Identify susceptible grasses and add 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues. Inhibits fatty acid production, cell membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family  Cyclohexanedione
CRANBERRIES—Established Beds
•  clopyralid (Stinger)
Rate  0.1 to 0.25 lb ai/A (0.25 to 0.66 pint/A)
Time  Apply only when cranberries are not actively growing. In new plantings this begins when cranberry vines go dormant in late fall and ends with budbreak. The second application period is after fruit set up to 60 days before harvest.
Remarks  Vines growing under the weed canopy may be sensitive to Stinger. Identify susceptible weed species (legume and composite families), and apply postemergence when weed canopy becomes visible. Results are best when applied before weeds mature. Do not exceed 0.67 pint/A per season. Do not add surfactant or crop oil. Special local needs labels WA-030006 and OR-030009.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  mesotrione (Callisto)
Rate  0.33 to 0.67 lb ai/A (4 to 8 oz/A)
Time  Apply only after budbreak but less than 45 days before flooding.
Remarks  Use a surfactant or crop oil as recommended by the label. 
Caution  Avoid using crop oils that injure cranberry vines. Do not exceed 16 fl oz/A or two applications per year. Allow at least 14 days between treatments.
Site of action  Group 28:  inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)
Chemical family  Triketone
•  norflurazon (Evital)
Rate  1 to 6 lb ai/A (20 to 120 lb/A product)
Time  Apply midwinter to early spring, before new vine growth begins.
Remarks  Use lower rates not exceeding 4 lb ai/A on sandy soils low in organic matter; on sensitive hybrid varieties such as ‘Stevens’ and ‘Pilgrim’; on young plants; or on beds with weak vines. Higher rates are required on older beds with higher organic content. Some growers and researchers report reduced crop yields, especially with new hybrids, when the product is applied in consecutive years. Injury may occur if applications overlap or if water stands in low, wet areas. Use lower rates and alternate with other herbicides to reduce possible injury. 
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  Pyridazinone
•  dichlobenil (Casoron)
Rate  1.2 to 4 lb ai/A (30 to 100 lb/A product)
Time  Apply from midwinter to early spring, before bud break.
Remarks  Results on sandy soils usually are best with split applications in midwinter to early spring. Allow 3 to 6 wk between treatments. Do not exceed 4 lb ai/A (100 lb/A) total per year. Irrigation or rain should follow applications to minimize vaporization and loss of chemical. Use higher rates only on very weedy beds and organic soils. Plants will temporarily redden after spring applications. 
Caution  Do not apply at or beyond popcorn stage or on newly sanded or new beds. Injury may occur where applications overlap or where water stands in low wet areas. Use lower rates (1.2 to 2.3 lb ai/A) on soils low in organic matter. Continued use at medium to high rates on sandier soils will result in a decline in production and plant health. 
Site of action  Group 20: inhibits cell wall synthesis Site A
Chemical family  Nitrile
•  napropamide (Devrinol 10G or Devrinol 50DF)
Rate  In sand beds 4 to 6 lb ai/A (40 to 60 lb/A of 10G formulation or 8 to 12 lb/A of 50DF formulation);  In peat beds: 6 to 9 lb ai/A (60 to 90 lb/A of 10G formulation or 12 to 18 lb/A of 50DF formulation)
Time  Apply before weeds begin to germinate and before spring growth begins, in mid-February to mid-March. 
Remarks  Requires ample rain or irrigation to activate. On 1-yr-old beds, use lower rates. Crop may be injured at high rates. Control may lessen with repeated use. Inhibits root and shoot growth.
Caution  Do not apply after buds begin to swell.
Site of action  Group 15: inhibits very long chain fatty acid synthesis
Chemical family  Acetamide
•  2,4-D low-volatile ester (Riverdale 2,4-D Granules)
Rate  2 to 4 lb ae/A (10 to 20 lb/A product)
Time  Apply winter to early spring while cranberries are dormant and leaves are completely dry.
Remarks  Use higher rates as spot treatments on certain perennial weeds only; use lower rates in combination with other herbicides. Experience suggests moderate rates (3 lb ae/A), combined with dichlobenil and applied in split treatments (half in February, half in March) may improve control of some of the more persistent perennial weeds. Mimics natural plant hormones.
Site of action  Group 4: synthetic auxin
Chemical family   Phenoxy acetic acid
•  clethodim (numerous products and formulations)
Rate  0.94 to 0.125 lb ai/A (6 to 8 oz of 2EC formulation)
Time  Apply to actively growing grasses, including annual bluegrass, at growth stage listed on label using 0.5 to 1% nonphytotoxic crop oil or 0.25% nonionic surfactant. Preharvest interval is 30 days.
Remarks  On label, carefully read about adjuvants, effects of rain within 1 hr, application of other pesticides, and cultivation. 
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitors
Chemical family  Cyclohexanedione
•  sethoxydim (Poast)
Rate  Spray—0.28 to 0.47 lb ai/A (1.5 to 2.5 pints/A product); spot treat—2 oz or 4 Tbsp/gal water + 2.5 oz or 4 Tbsp crop oil concentrate
Time  Apply at optimum growth stage listed on the label. Preharvest interval is 60 days.
Remarks  Identify susceptible grasses and add 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues. Inhibits fatty acid production, cell membranes, and new growth.
Site of action  Group 1: acetyl CoA carboxylase (ACCase) inhibitors
Chemical family  Cyclohexanedione
CRANBERRIES—Swab or Wick Treatment
•  glyphosate (several products)
Rate  20% solution for wick wiper
Time  Apply after fruit set. Preharvest interval is 30 days. Apply when weeds are actively growing and at least 6 inches taller than cranberries. 
Remarks  See label for growth stage of specific weeds. Retreatment may be necessary. Slower ground speed and/or application with wick to both sides of dense infestations may improve results. Avoid drips or contact with desirable foliage. Inhibits three amino acids and protein synthesis.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  glyphosate (several products)
Rate  Cut stump treatments
Time  Apply a 50% solution for woody brush control in and around cranberry bogs.
Caution  Preharvest interval is 30 days.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  sulfosate (Touchdown IQ)
Rate  25% solution for wick wiper
Time  Apply to target weeds, avoiding contact with vines.
Remarks  Use only on nonbearing vines. 
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  clopyralid (Stinger)
Rate  2% solution for wick wiper
Time  Use after budbreak to control late-emerging weeds.
Remarks Apply to target weeds, avoiding contact with vines.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
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