Weed Management

Prepared by Hilary A. Sandler and Katherine M. Ghantous

New Herbicides and Updates 

Check our web site (ag.umass.edu/cranberry) and upcoming newsletters for further information about any new uses or products. UPI has discontinued the production of Devrinol 10G and 50DF formulation. It is still legal to use remaining stock. Follow the label of the product you are using!

Cranberries have been removed from the Princep label. Other products with the same active ingredient (simazine), such as Simazine 4L, are labeled for cranberry and registered in Massachusetts. We are unaware of product availability or efficacy. 

Special Labels available for herbicides (see Cranberry Station website under “Services” for labels):

• Callisto: Special Local Need (24c) label for concentrated spot-treatment, and adjusted adjuvant rate for chemigation.
• Cutrine-Plus: 24c for management of algae in late water flood. See Late Water section.
• Devrinol 2-XT: 24c for the use of 1) multiple applications on new plantings and 2) multiple applications before bloom or after harvest on established beds.
• Intensity One: 24c allows for application by chemigation, and application between hook and fruitset. NOTE: The 24c for Intensity has been rescinded, and ONLY Intensity One can be chemigated.
• QuinStar: 2ee to permit shorter injection times.
• Spartan 4F/Zeus XC: 24c to allow use for control of moss and other susceptible weeds. NOTE: The 24c for Spartan was added in 2023, and will be the only sulfentrazone available when Zeus expires December 31, 2024.

Weed Life Cycles 

Annual plants complete their life cycle in one year and reproduce by seed (e.g., dodder). They germinate from seeds, grow to maturity, flower, and make seeds all within a single growing season. Biennial plants take two years to complete their life cycle. They typically germinate from seeds and grow vegetatively in the first year, then enter a period of dormancy over the winter. They flower and make seeds the following growing season. Perennial plants can live for many years and may reproduce by seed, runners, rhizomes, etc.  Most of the weeds in cranberry production are perennials. With the exception of dodder, annual weeds are much less common and easier to control than perennials. However, infestations of annual weeds should not be taken lightly, especially on new plantings. Annual plants are designated with an (A). Unless otherwise noted, all other weeds are perennials.

Weed Priority Ratings (Very High, High, Medium, and Low)

The Priority Rating of each weed is determined by considering the following: 1) impact of a given weed on cranberry, 2) the biological form or type of weed, 3) its invasive and/or reproductive capacity, and 4) its adaptation to the cranberry habitat. Each criterion has 4 possible values (1, 2, 4, or 8). The values of the 4 criteria are added together to determine the rating. Totals of 24 to 32 points = Very High Priority, 16 to 23 = High, 8 to 15 = Medium, and 1 to 7 = Low. Please see the ID Guide for Weeds in Cranberries (available for purchase at the Cranberry Station) for the specific ranking criteria of each weed (pp. 261-272) for more details. Page numbers in the ID Guide are provided in this section as appropriate. Some weeds are in the Chart Book but were not included in the ID Guide and have been given a Priority Rating by the Extension Weed Specialist.

Weed Mapping

Weed maps can help you organize the management of your weed problems, especially with perennial weeds. Weed maps should be done every few years, depending on weed pressure and management objectives. Several steps are involved: 1) Correctly identify the weeds, 2) Document the location of the weeds (by drawings, GPS, or photographs), and 3) Designate a priority rating to the weed. Growers may change and adapt weeds into priority ratings to best fit their own management program.

Weeds

Herbicides

OFF-BOG AQUATIC WEED CONTROL

OFF-BOG USE: WEED MANAGEMENT OUTSIDE OF PRODUCTION AREAS 

• AQUATIC WEEDS. Reports of grower problems with aquatic weeds have been increasing. Aquatic weeds can be submersed, floating plants, floating leaf plants or emergent plants. Common aquatic species for our area may include fanwort, variable watermilfoil, bladderwort, hydrilla, duckweed, and water lilies. Be sure to get a correct identification of the weed problem before treating. Treatment of some water areas may require a permit. Non-chemical methods (e.g., harvesting, suction, hand pulling, dredging) are available but are very expensive. The use of grass carp for aquatic weed control is NOT permitted per MA Fish and Wildlife. Call 508-389-6300 for more information.
• DIQUAT. This herbicide should only be used on water weeds growing in areas outside of the bog. Do not use in any ditch associated with the production area. Diquat will control water weeds such as bladderwort, coontail, elodea, and pondweeds. A non-ionic surfactant (e.g., Induce, Activator 90) may improve performance. Check the label for rate information, and directions on spot treating surface weeds.
• RODEO. This glyphosate product can only be used to control weeds that occur outside of the production area. Application is spray to wet leaf surfaces, not to runoff. Extremely cool or cloudy weather following application may slow the activity of this herbicide. Best control is obtained when plants are at late growth stages approaching maturity. Weeds under stress will not be controlled as well as healthy plants. Rainfall within 6 hours of application may reduce effectiveness, and heavy rainfall within 2 hours of application may necessitate reapplication. Do not add ammonium sulfate to Rodeo mixtures.
• ALGAEICIDES 
  Algaecides for control of algae (green scum) are usually prescribed on an acre-foot basis. An acre-foot is the amount of water needed to cover one acre of bog with one foot of water (~300,000 gallons of water). These include products like Cutrine Plus (can be used both off- and on-bog, see Late Water section), which are labeled for use in ponds, ditches, and canals.  Read all product labels carefully before using.
• NAUTIQUE (by SePro) is a copper carbonate (double-chelated copper formulation) product that is labeled to control floating, emerged, and submerged vegetation in still or flowing aquatic sites such as reservoirs, ponds, slow-flowing water bodies, crop and non-crop irrigation systems.  Use lower rates if carbonate hardness of the water is less than 50 ppm (this is generally the case in MA); as water hardness increases (>50 ppm), efficacy may be decreased and non-target toxicity may be increased. If applying to public waters, check with the local authorities for permit process. Nautique can be mixed with other aquatic herbicides; check the label. When applying to irrigation ponds, hold water for a minimum of 3 hours before irrigating plants. It is highly corrosive and carries a DANGER label. It may be fatal if absorbed through the skin. Be very careful with this product!! Wear all recommended protective equipment. Application rate varies by vegetation density and depth of treated area. Please read the label. If you have any questions, please consult with a Weed or Aquatic Weed Extension specialist prior to treating.
• NOTE ON IRRIGATION SOURCES TREATED WITH AQUATIC HERBICIDES: In some instances, municipalities or homeowner associations (or similar) may opt to apply aquatic herbicides to water bodies that cranberry growers use for irrigation or flooding. Some products may or may not have a tolerance, some have ‘incidental tolerances’ and some are tolerance-exempt. Depending on the product and timing of application, the impact to your farm operation could be small or great. Please reach out to the Station and your handler if you anticipate that a situation might occur.

OFF-BOG WOODY AND BROADLEAF PERENNIALS CONTROL 

(not in ditches or canal banks)

Hand pulling is most beneficial in Spring and early Summer when the soil is moist and the plants are fairly small. 

CROSSBOW, WEEDONE (2,4-D). Crossbow and Weedone are labeled for non-bog use only and are State Restricted Use pesticides. Be cautious! Crossbow contains triclopyr for which there is no food tolerance. Do not use Crossbow or Weedone on dikes or canal banks. Use it only on weeds located far away from the bog.  These products have considerable potential to evaporate and cause crop injury. They have the potential to drift far from the site of application, and can injure nearby plants such as apple trees, grapes, etc. Avoid applying 2,4-D on hot, sunny, and humid days when there is little air movement. 2,4-D products can be highly effective at controlling some weeds.

• Weedone 650 (WSSA/HRAC Group: 4)    
  Follow spot treatment instructions    
  Spray to wet. Avoid drift onto bog. Controls woody plants on roadsides and non-crop areas.
• Crossbow (WSSA/HRAC Group: 4)    
  1-1.5% solution, see spot treatment instructions    
  Drift to desirable plants may cause injury (esp. grapes and tomatoes). Do not apply to water. Read the label! See Notes on 2,4-D.

RENOVATION AND NON-PRODUCING BOGS

• FUMIGANTS. Basamid (dazomet) and Vapam (metam-sodium) are soil fumigants that can be used on cranberry beds. They can only be used if fruit will not be harvested and delivered for 12 months post-application. DO NOT USE FUMIGANTS AS A SPOT-TREATMENT IF ANY VINES WITHIN A DIKED SECTION WILL BE HARVESTED. If it is used on part of section, no fruit can be harvested or delivered from the entire (contiguous) section. If you are renovating an entire section, a portion of that section can be spot-treated with a fumigant. More information on the use of fumigants may be found in the Planting New Cranberry Beds Fact Sheet (http://ag.umass.edu/cranberry/fact-sheets). Contact the Weed Specialist if you have any questions about using these chemicals.
• You must complete EPA fumigant training before applying any fumigant. You must get certified/pass the module on EPA's web site. As required by updated soil fumigant product labels, certified applicators must successfully complete an EPA-approved training program covering the new soil fumigant provisions. Please go to the EPA’s web site for more information:
  https://www.epa.gov/soil-fumigants/soil-fumigant-training-certified-app…
• Note: There is a provision that if you are already certified in a soil fumigation (sub)category and your state is listed with additional training option and requirements, you can bypass the training. Massachusetts is NOT one of these states! So you must take and pass the modules.  
• REGLONE, and others (Diquat dibromide). Non-selective herbicide. Reglone and other diquat products registered for use on non-producing beds should only be used on bogs that will be renovated or will not be harvested for 1 year. The intended use is as a site-preparation product, not for use for spot weed control on an active farm. This product works as a plant desiccant and should be used as a directed spray. Reglone cannot be applied by chemigation. Use 1.5-2 pt/A in a minimum of 15 gallons water by ground. May need repeat applications. Add NIS. WSSA/HRAC Group: 22.
• FUSILADE (Fluazifop). This selective grass herbicide can only be used on non-producing bogs. It is used postemergence for control of true grasses. Sprayed grass will turn yellow and die back over a 1-4 week period depending on climatic conditions. It is rainfast after 1 hour. Add a COC at 0.5-1% v:v or 0.25-0.5% v:v if using a NIS. Use 0.75 fl oz herbicide per gallon water. REI is 12 hr. WSSA/HRAC Group: 1.

DITCH MANAGEMENT

• WOODY AND BROADLEAF PERENNIALS ON DIKES (BOG-SIDE)
  Cultural controls include mowing the ditch and dike areas during the summer months. Some areas may need to be done more than once. Hand pulling is most beneficial in the spring and early summer when the soil is moist and the plants are fairly small. Controlling weeds on the dikes may be useful in reducing spread of these weeds onto bogs.
• DITCH WEEDS (e.g., Arrowhead, Pickerelweed, Pond lilies, Bur-reed, Duckweed) 
  Clean ditches by hand or mechanically preferably twice a year. Draining ditches can sometimes be helpful in killing some aquatic weeds (e.g., duckweed). Preemergence herbicides registered for use on the bog may NOT be used in the ditches for weed control. Roundup use is permitted in dry ditches as a wipe or a spray. See notes on Roundup. Flame cultivation may be an effective nonchemical tool for ditch weed management. 

CAUTIONS AND OTHER NOTES

1. Chemicals not registered for use on cranberries must not be used.
2. Herbicide use may weaken vines and crops may be reduced.
3. To be most effective, rain should follow the application of any dry herbicide formulation within 4 days or the bog should be irrigated.
4. Wash equipment with soap (or detergent) and water immediately after using. Rinse with ammonia after using hormone-type herbicides (such as 2,4-D).
5. Hand wiping with glyphosate products is often practical with some weeds if roots are weakened. This is particularly useful for dewberries after late water or a summer flood.
6. Mowing of tall weeds helps to prevent shading and reduces seed formation.
7. Late water causes general reduction of annual grasses and may reduce dewberry populations and re-growth.
8. Agricultural burning of brush or grass is allowed under regulations from the Director of Air Pollution Control, Southeastern Office of the Dept. of Environmental Protection and under permit from the local fire chief.
9. Review the Weed Management BMP in the UMass Best Management Practices Guide: 
   ag.umass.edu/cranberry/publications-resources/best-management-practices