Maine Cranberry Management Calendar

February: This is typically when Maine growers will apply sand (if needed). A 2006-2008 study out of Massachusetts has steered researchers there towards recommending that a good all-around canopy management strategy appears to be this: Sand every 5 to 6 years, with pruning in between. For the least impact on yield, the study found that whenever a ‘sanding’ or ‘pruning’ is done, it should be done on the light side (~half inch of sand in the case of sanding, and a single pass with the pruner in the case of pruning).


  • Frost Protection: Know the tolerance levels for your variety or varieties, and monitor your bud stage throughout the month (use the bud stage that the majority of your vines are showing).
  • Mid to Late April: Pre-emergence herbicides need to be applied before cranberry vines break dormancy. For a list of herbicides, and individual target weeds, check the weeds portion of the Maine Cranberry Pest Management Guide.
  • Late April: Late-Water Flood (MS Word) | Late-Water Flood (pdf). Do not apply this flood if the buds have broken dormancy, or if the winter has been severely cold and long, oxygen deficiency conditions are suspected, or if the bed has been sanded since the preceding fall. The flood provides very good control of fruit rot fungi, boosts keeping quality, and kills overwintering Cranberry Fruitworm and may eliminate the need for sprays for this insect during the Late-water year (Expect 90% or more Cranberry Fruitworm control if the flood is held for four weeks, 40-50% control if less than four weeks); virtually wipes out Southern Red Mite infestations and may suppress False Armyworm and Gypsy Moth larval populations; can delay the development of weeds (suppresses growth of some perennials, most notably brambles; the flood does not control dodder)


  • After terminal buds have broken dormancy & begun to swell or grow: The approximate window for spraying for Upright Dieback control is April 30 – May 20. For Washington County growers, the target window is likely a bit later (May 6 – 26). But, exact timing depends on whether the variety is early or late-season.  For a list of available fungicides you can use, and details about Upright Dieback disease, consult the Maine Cranberry Pest Management Guide. Note:  Fungicides will not cure upright dieback but will prevent the spread of the infection.
  • Callisto® for weeds just starting to emerge (but avoid using it year after year so as not to encourage resistance): (best if <5″ tall, yet growing  actively) (~From May to 45 days before harvest or flooding, and not during bloom) Callisto® is reportedly an extremely good choice for weed control, having both pre-emergence activity as well as post-emergence activity (especially when weeds are <5″ tall), and you are encouraged to wait for that stage.  If you apply too early, some weeds with vast root systems–such as cinquefoil–can quickly recover. Thus, for cinquefoil, wait until the first flush of new growth has taken place.  The maximum application rate is 8 oz/acre/application; no more than two apps. per season, and split apps. need to be at least 14 days apart. Callisto® is effective against a large number of different weeds (will control most all annual broadleaf weeds if under 5″ tall), but plan on several years of treatment in order to achieve permanent control of many perennial weeds, especially yellow loosestrife/swamp candles. Birdsfoot trefoil and other Lotus members are very sensitive to Callisto® (but more difficult to control if they are completely covering over the cranberry canopy). Cranberry vines are highly tolerant of Callisto® – they can readily metabolize its active ingredient (mesotrione).
  • ~May 14 – May 31 (vegetative buds elongated 1/2″ and flowering buds at bud break stage): Cranberry tipworm often begins, but in recent years this pest has not been as much of a problem as it was in the late 1990s and early 2000s.  Also, for reasons unknown, it has also been showing up a month or more later than in the past (so late June rather than late May).  If tipworm does show up at your location, it is the adult flies that appear first, followed by eggs and larvae once new tips have begun to grow. Overwintering pupae will be hatching out into flies (the length of this period is a bit uncertain and probably varies from year to year).  Individual flies only live for about three days (five at most), so right out of the gate they are busy mating and laying eggs on the terminal leaves of uprights (mostly on the tips of brand new uprights sprouting up from the runners).  The more dormant the upright, the less likely its chances of being chosen for egg-deposition by the female tipworm fly. Conventional wisdom is to treat at the peak of egg hatch, or slightly before that period in the case of any material that provides a good residual or has systemic activity.  The window for either of these timings is somewhat narrow.
  • ~May 20th – Early June (tip elongation):
    • False Armyworm larvae begin (If no Late Water flood was used). These cutworms have been consistently found in significant numbers on Maine cranberry beds annually. The larvae feed on leaves, stems and buds (basically consume entire uprights), and get quite big when mature (2” long), at which point (late June into July) they feed almost exclusively at night. Sweepnet-Captured ‘First Dates’: 6/6/97, 5/28/98, 5/28/99*, 5/24/00, 5/31/01, 5/13/02*, 5/24/05, 5/25/07, 5/14/08, 5/14/09, 5/16/2013*♦, 5/20/2014*♦ (Average of these = May 23rd)
    • 1st-generation Blackheaded fireworm larvae begin! Spend some time visually scanning for upright tips with terminal leaves that have been webbed tightly together!  Break off any tip of that sort, and carefully tease apart the terminal leaves.  If a small larva suddenly squirms out, wriggling backwards and possibly right across your hand and down to the ground (often attached to a strand of silk)…and if this happens before you’ve even blinked, then you’ve probably encountered a fireworm larva. You should then sweep to see if you pick up any in your net.  They do not get picked up in sweeps very easily, so if you average even just one larva per 25 sweeps, you may well be justified in taking action (depending on your history with this pest, your expected crop value, etc.). View the Maine Cranberry Pest Management Guide for the most current recommended Action Threshold (AT) to consider using (traditional AT is 1), and for a list of control materials.  Infestations of 2nd-generation larvae are far more dangerous, because their numbers are much higher, especially, of course, if any 1st-generation populations are left uncontrolled.  Infestations of both generations are usually patchy, at least at first, and larvae tend to be more numerous along edges. Spot-treatment is desirable in such cases. Sweepnet-captured ‘First Dates’ for 1st-generation larvae: 6/12/06, 5/25/07, 5/14/08, 5/14/09, 5/16/13, 5/20/14, 5/27/17, 5/21/18 (Average of these = May 22nd); See also the Pest Report each year for news of Maine’s first detection of 1st-generation fireworm larvae.


  • All of June: Cranberry Tipworm
  • All of June: Cranberry Weevil (spring brood)
  • All of June: False Armyworm larvae
  • All of June: Blackheaded Fireworm larvae
  • All of June: Cranberry Blossomworm larvae (Average Start Date for Maine = May 29th but most often they begin to appear in early June)
  • All of June: Blunt-nosed Leafhopper (nymphal stages) (this pest is a vector of Cranberry False Blossom disease)
  • First Week of June (plus or minus a week): Gypsy Moth caterpillars begin to show up on beds, mostly blown in from forested areas though they can also overwinter right on the beds. Their numbers can be fairly numerous in some years, although zero were seen during the entire 2009 season by UMaine Extension’s Cranberry Professional.  Add the number of these larvae to any cutworms and humped green fruitworms found when using a thresholds table. This insect is cyclic and in the past has undergone major outbreaks every 9 to 10 years in the northeastern U.S. and Canada. The larva is one of North America’s most devastating forest pests (especially fond of oak and aspen). It has no problem eating cranberry foliage as well. Check for patchy infestations that can be spot-treated, e.g. along bed edges facing trees that might be infested. Check any previously infested areas. Early detection is key: larvae consume terminal buds and any new growth that has begun. Some Sweepnet ‘First Dates’: 5/29/00, 5/20/01, 6/13/02, 6/12/06, 6/6/07, 5/16/2013 (central Maine), 5/21/2018 (western Maine) (Average of these = May 30th)
  • Late June: Spanworms may become increasingly abundant.



  • Cranberry Tipworm (any remaining larval stages should finally begin to wind down for the year by month’s end)
  • 2nd-Generation Blackheaded Fireworm larvae (this is the generation to really watch out for, particularly if you saw threshold levels–or higher–of 1st-generation larvae and are uncertain as to the effectiveness of any control actions you may have taken earlier in the season)
  • All of August: Cranberry Fruitworm larvae
  • Late August: Red-headed Flea Beetles (adults begin to show up and will continue well into September) – High levels of them can impact bud development for the following year. They feed primarily on the undersides of the leaves, consuming the outer surface layers and leaving only the veins behind.  They also will gouge the berries.
  • Cranberry Tissue Testing: Tissue samples should be taken during the last two weeks of August or during the first week or two of September. The reason for this is that the concentrations of the 13 required minerals (macronutrients) are stable during this period. Also, the standard values against which the results are compared are based on sampling that was done during this period.

September – October:

  • Early September: Still time for doing some Cranberry Tissue Testing
  • Throughout September: Red-headed Flea Beetles (adults) They begin to show up in August but will often linger well into September.
  • Frost Protection: Know the tolerance levels for your variety or varieties, and monitor your berry color (go with the color that the majority of your berries are showing).
  • Late September – October: Harvest Time
  • Plan your harvest water-flow from bed to bed such that, if possible, water is not moved from disease-infested or weed-infested beds into clean beds or less infested beds.


  • Trash Flooding: Flooding after harvest is a good means of removing ‘trash’ — i.e. dead cranberry leaves, twigs, and bruised berries.  On a windy day, the ‘trash’ will be driven to a corner or edge where it can be skimmed from the water and then disposed of at a location far from the bed.  Dead leaves and leftover berries serve as a source of disease inoculum and provide habitat for insect pests.  Removing this material may reduce how often you need to sand.
  • Post-Harvest Flooding: Ongoing research in Massachusetts (and grower practice) is finding that flooding for up to 4 weeks post-harvest suppresses dewberry plants and cranberry fruitworm.  In some studies, mortality of overwintering cranberry fruitworm (in their hibernacula/cocoons on the bed) was close to 100%.  No reduction of the crop has been reported after several years of experimentation with this particular flood.

Fall Chores:

    • Thoroughly clean all equipment used for harvest. Use a pressure washer to clean debris from tractors, beaters, blowers, conveyers, berry pumps, booms, trucks, gondolas, etc. As you clean note anything that needs to be repaired, re-engineered, or painted.
    • Throw out or recycle junk that is no longer useful to you. Don’t let junk pile up around the farm. Inventory fasteners, welding supplies, lubricants, solvents, filters, etc. Do you have needed items on hand which might reduce emergency trips to town?
    • Take a few moments to review your production records such as fertilizer and pesticide applications and make sure they are legible and accurate. Make a copy to store in another secure location besides your primary office.
    • Take a few moments to consider harvest. What went well? What didn’t work very well that is under your control? Did vital equipment break down? If so, what can be done to avoid similar problems next year?
    • Consider having an employee roundtable (if applicable to your situation) where all are free to reflect on the entire crop season providing feedback on what went well and what didn’t. Invite employees to offer suggestions of what might be done differently in the future.
    • Review your nutrient management plan. Did your actual application of nutrients follow your plan? How did you decide to vary from your plan? What criteria did you use to make your decision(s)? How will this change your plan for the future?
    • Have you mapped where you had problems with specific weeds? If you know where the troublesome weeds were can you use that information to make better weed management decisions next year?
    • Ponder mistakes that were made with regard to pest management, personnel management, fertilizer, irrigation, drainage, etc. What policies or approaches could change next year to good advantage?
    • Inventory any of your unused fertilizer or pesticides. Make sure pesticides are appropriately stored in a clean, dry and secure location. Ideally, pesticides are stored in a location separate from machinery, etc.
    • Check the oil, tire pressure, brake fluid, steering fluid and other hydraulics on all equipment and fill as necessary.
    • Continue to monitor weather through the fall and be prepared to flood beds or irrigate if precipitous temperature drops are forecast.
    • Should you use any fall fertilizer? (see below)

Should you use any fall fertilizer?

By Dr. Carolyn DeMoranville [Excerpted from the Sept. 2009 issue of the UMass Cranberry Experiment Station’s cranberry newsletter. Used with permission.]

Each fall, growers ask me – should I apply fall fertilizer? The answer for many growers may be a cautious yes if the plants are looking weak or the crop is heavy. If this is your situation – how should you decide if this is needed on your bog and what should you use? First look at your vines, crop, and fertilizer use so far this year. Follow the decision tree below to decide if fall fertilizer is right for you:

Question Answer Fall fertilizer?
Are your vines lush or long? Yes No
Did you have a big crop this year? No No
Have you already applied more than
30 lb. N (50 lb for hybrids)?
Yes Probably not
If you have deep organic soil with little need for
early fertilizer normally
Yes Probably not

But if your fertilizer use was modest, the vines are not pumped up, and you had a great crop, then consider using fall fertilizer. Choose a material and apply it between early and mid-November when the soil has dried from harvest but well ahead of the winter flood.

So what to use and how much? My best recommendation is to apply 5 lb/acre N, little or no P and as much K as you can find among the available fertilizer choices. The N will build up the vines, P is not needed in the fall (natural release from the soil is occurring), and added K may enhance hardiness. Also, N and K are the two elements that are removed in the greatest quantity in harvested fruit; P is at much lower concentrations in the berries.

Most growers try to apply in 100 pound increments for ease and uniformity of application, so let’s discuss fall fertilizer choices on that basis.

Look at your choices of fertilizer and determine how much N, P, and K (in pounds) would be applied in 100 lb of fertilizer material. Remember that you are looking for about 5 lb/acre N.

Choice N P K
5-15-30 5 6.6 24.9
3-13-26 3 5.7 16.6
5-10-10 5 4.4 8.3
8-32-16 8 14.1 13.3
6-24-24 6 10.6 19.9
5-5-20 5 2.2 16.6

Many common materials (like 12-24-12, 15-15-15, and 18-8-18) are just too high in N. Some of the choices in the table would give around the 5 lb/acre N rate with 100 lb/acre of fertilizer but would add much more P than is desired, creating an environmental risk. Those include the 8-32-16 and the 6-24-24. While both give about the right N and fairly high K, seasonal P will exceed 20 lb/acre even if you used 18-8-18 during the season with these choices. If you choose the 8-32-16 at 75 lb/acre (to get the N down closer to the recommended 5 lb/acre), you still add more than 10 lb P/acre and now only about 10 lb K/acre.

The best off-the-shelf choices are 5-15-30 (good N, lots of K, moderate P) or 3-13-26 if you want less than 5 lb/acre N. I do not recommend using 3-13-26 at higher than 100 lb/acre rates to boost N since then you are paying for more materials to apply and again increasing P. The 5-10-10 is a good choice but a bit lower in K. This should be fine if your vines aren’t stressed or crunchy. If they are, I would prefer the 5-15-30 to get the additional K.

The best material for low P in the table is the 5-5-20. This gives very low P, target N and substantial K.

What about fish fertilizer? An application of 5-10 gal/acre can replace granular fall fertilizer. If you have pop-up sprinklers and can apply this post-harvest, that is an additional option. Remember, this fertilizer is taken up through the roots, so water it in enough to wash it to the soil.

Finally, what about zero P fertilizers? These are predominantly formulated for turf and most have 25-30 lb N in a 100 lb/acre application (first number is 25 to 30) leading to issues with applying the low N desired in the fall. If you can find one with N in the desired range, by all means use that.

The bottom line? — if you use fall fertilizer, choose one with the lowest possible P.

Disclaimer: Pesticide registration status is subject to change and varies from state to state; therefore the author and the University of Maine Cooperative Extension cannot assume liability for any pesticide recommendations. It is the responsibility of the pesticide applicator to verify the registration status of any pesticide before applying it. The label is the law! Always read and follow the label when applying pesticides. Use of product names does not imply endorsement.