Cranberry Station Newsletter 2025 Vol. 26:3

ALERT! Winter Injury Appearing on Beds this Spring

by Katie Ghantous with imput from Peter Jeranyama

It has come to our attention that there are widespread reports of winter injury showing up on MA cranberry bogs this spring as both winterkill (desiccated uprights) and injury to cranberry buds on non-desiccated uprights. Reports range from mild to severe and are being seen in all areas including the Cape. In some areas the winterkill injury is extensive, and it is increasingly appearing that the MA crop yield will be impacted. Some growers have been estimating that they will be down by as much as 30% this year.

We experienced a very cold period this winter. While it provided a rare opportunity for some ice sanding, it also created a potentially injurious time for the cranberry vines. The evening temperatures averaged 18.6ºF in January and 20.2ºF in February. January had 5 nights with temperatures below 9 degrees and February 11 and 12 had low night temperatures of 2 ºF.

To make matters more complicated, there were freeze and thaw cycles. The cold snaps were followed by some days of thawing and then followed by MORE cold and windy days. Some beds that were flooded for the first cold period lost some ice/water and vines were then exposed for the second cold period. We are hearing that many growers feel that the injury happened during the second cold period. There are some beds that cannot hold water, and it is expected that those sites could have incurred more extensive injury (most likely from both cold periods).

During the Crop Summit held at the Cranberry Station in December 2024, there was a lot of discussion about the drought conditions during harvest and whether that would impact the vines for next year. One grower stated that in his many years of experience, vines can tolerate one major stress per season, but a second stress causes major problems. This week, more than one grower has mention to me that they think the dry fall may have played into the vines being more prone to winter injury.

WHAT IS WINTERKILL? 

Cranberry vines may be injured or killed by severe winter weather. The most common injury, referred to as “winterkill”, is classified as a physiological drought. This can occur when the root zone is frozen. Unlike deciduous woody plants, cranberry plants hold onto their leaves all year long which makes them vulnerable to winterkill. Water in leaf and bud tissues is lost from the vines due to wind and evaporation and it cannot be replaced because the water in the soil is frozen and unavailable to be taken up by the cranberry roots. According to the 2008 Cranberry Production Guide, in addition to direct damage to buds the “desiccation may result in leaf loss in the spring. Since cranberries accumulate nonstructural carbohydrates (the fuel for metabolism and growth) in the spring, the loss of leaf tissue may have a significant impact on subsequent production of new growth and fruit.”

Winter floods are used to protect the vines when winterkill conditions are predicted (root zone is frozen to a depth of 4 inches, air temperature is below freezing, and strong winds (10 mph or greater) are expected to occur). To be optimally effective, the flood should be deep enough to cover all vine tips. In many cases, this is not possible if the bed is out of grade, has tufty spots, or other circumstances where some vines are not fully protected by the flood. Inherent varietal differences may influence the severity of the winter injury. 

In most cases where winterkill symptoms show up, the uprights are affected but the plant itself is still alive and will recover. Most of the plant was protected, and the desiccation has not been severe enough to kill down to the roots. 

WHAT DO I DO IF I HAVE SYMPTOMS ON MY BOG?

After reaching out to colleagues in other regions that experience winterkill conditions like New Jersey and Quebec, it turns out that there are no formal recommendations for how to deal with winterkill anywhere! Most of the research focuses on preventing winterkill, and there is not much research focused on how to manage beds with winterkill injury.

The Chart Book states that for winter injury:

• Start fertilizer early. If leaf drop occurs after withdrawal of winter flood, early spring fertilizer applications will aid in recovery by encouraging rapid, early production of new leaves. Do not skip spring fertilizer. Note that the Chart Book recommendation is that you can apply up to 20% of the total N between roughneck and hook.  If you do not usually apply fertilizer that early but have winterkill you may want to consider incorporating that timing into your program this year.

• SulPoMag. SulPoMag (or similar material) at 100-200 lb/A may also aid recovery. If your injury is severe you may want to select the higher end of the rate range.

We have had growers question whether or not to alter their fertilizer programs (either increase or decrease N amounts, add in other fertilizers like Sul-po-mag, etc.) to compensate for injury and help vines recover. 

It is important to consider adjusting the total amount of Nitrogen you plan to apply this year. Just as you would add more N if you expect a large crop, if you expect your crop to be smaller than usual you should think about adjusting the amount of N down so as not to encourage excessive vegetative growth. 

WINTER INJURY TO CRANBERRY BUDS ON NON-DESICCATED UPRIGHTS. 

On State Bog, we have been seeing some uprights (not obviously showing signs of winterkill) present with buds that are damaged. Cranberry buds that will grow into flowering uprights contain multiple floral initials. Not every flower will result in a fruit. If some of those floral initials are damaged from winter or spring frost, that upright can still go on to successfully bear fruit. Some injury does not necessarily translate into a loss in yield. Peter’s research shows that a cranberry bud typically has four to six floral initials and damage to two floral initials means the remaining two to four initials will produce flowers and result in fruit production. So, moving into the frost season with some preexisting winter injury to buds is not a doom scenario. If the winter damage to buds was more extensive than one or two floral initials per bud, yield could be impacted.

To check a bud for injury, create a cross section to examine it. Remove the leaves around the bud, lay the upright on a flat surface, and cut through the bud half-way between the top of the bud and the point where the bud joins the stem. Use a sharp, thin blade - a razor blade works well. See the Frost Protection Guide for more information or reach out to us at the Cranberry Station for assistance!

News from the Cranberry Pathology Lab

by Leela S. Uppala and Salisu Sulley

LATE WATER (LW)- KEY BENEFITS AND GUIDELINES

As we approach the Late Water (LW) period, this is a great time to evaluate whether it’s the right option for your bog. Below is a brief overview of the key benefits and guidelines, including when LW is recommended and when it should be avoided. If you choose to hold Late Water, proper post-flood management is essential to maximize its benefits. Please refer to the 2024 Chart Book (pages 96–99) for detailed guidance.

What is Late Water: Late Water is a cost-effective, one-month spring flooding technique that can offer multiple agronomic and pest management advantages when applied under the right conditions.

Timing: Apply flood from mid-April to mid-May. Historically this has been between April 15 to May 15. If spring temperatures are unusually warm, this window may shift slightly. Ensure that your cranberry vines are still fully dormant before flooding. Recommended once every three years.

Key Benefits:

• Delays and compresses bloom into a shorter window.
• Improves fruit set, size uniformity, and quality.
• Suppresses pests: mites (especially Southern red mite, scale), spring caterpillars, cranberry fruitworm.
• Reduces weeds (e.g., dewberries/brambles) and fruit rot incidence.
• Enhances keeping quality and lowers nitrogen needs.

When is Late Water is Advised:

• If your bog looks healthy and not showing any signs of stress.
• The flower buds are still red and tight.
• If your bed was properly flooded at the periods of coldest temperatures.
• If the scale and/or fruit rot incidences were high in 2024.
• If you have access to good quality water supplies.

When is Late Water Not Advised:

• If you held late water in the past two years.
• If your bog produced a heavy crop in 2024.
• If the buds have broken dormancy.
• If the bed was sanded the previous year.
• If the bog is stressed and shows signs of winter injury.
• If your bog is severely out of grade. 

For more information, see the Flood Management BMP. If you have any questions, feel free to contact Leela Uppala at suppala[at]umass[dot]edu (suppala[at]umass[dot]edu) or 508-970-7644.

Special Local Needs 24(c) label for Cutrine Plus for algae control in late water floods Cutrine Plus is a liquid copper-based formulation that has been used for decades to control algae in late water floods. During recent reviews of the Chart Book, we realized that the Section 3 label language was ambiguous as to whether the application of Cutrine to flood waters was permitted under our conditions (as a result, we removed Cutrine Plus language from the 2021-2023 Chart Book). Working with the registrant, SePRO, we sought approval of an SLN that would clearly address its use as an application to flood waters in MA cranberry production. In March 2023, MDAR granted approval of the SLN. If you plan to use Cutrine-Plus, please obtain a copy of the SLN at https://ag.umass.edu/cranberry/services/special-pesticide-labels. 

Notes on using Cutrine-Plus. If your flood is shallow or if you have had scum problems in late water floods (LW) in the past, plan to treat 2 weeks into the flood period. Scout for algae and apply when growth is first visible on the water surface.  Remember that copper only prevents further algal growth (it does not eliminate existing scum), so prompt treatment is necessary.   

The material is injected into the sprinkler system running at 20 psi (e.g., when doing a 30-minute injection, you may continue running for 1-2 hours after to disperse the material). Rates are calculated using label information and the number of acre-feet to be treated. To calculate acre-feet, multiply the number of acres by the depth of the flood in feet. Multiply the desired rate (gallons per acre-feet based on chart from pesticide label) by the acre-feet of water you have calculated for the bed being treated. We typically recommend a rate in the range of 0.6-1.2 gal per acre-foot.   

News from the Extension Education and Entomology Lab

by Marty Sylvia

UPCOMING SPRING PESTICIDE CREDIT OPTIONS

Respirator Training! (2 credits)

• April 8, 2025

• 8:30-10:30 AM, hybrid option at CCCGA office

• Register through CCCGA

UMass Cranberry Pesticide Safety Meeting (4 credits)

• April 30, 2025

• 7:30-12:00 PM, hybrid option 

• $60 per person 

• see page 9 for payment form

UMass Cranberry Insect & Disease Clinic I (2 credits)

• May 7, 2025

• 7:30-9:30 AM, in-person UMass Cranberry Station

• No charge

UMass Cranberry Insect & Disease Clinic II (2 credits)

• May 21, 2025

• 7:30-9:30 AM, in-person UMass Cranberry Station

• No charge

SPRING WPS HANDLER TRAININGS

 Thursday, April 17, 2025, Friday, May 2, 2025, or Thursday, May 29, 2025

• 8:30 - 9:30 AM, hybrid option

• Cost is $5 per person

 Anyone working on the cranberry bogs (bogs that have been treated within 30 days) who does not have a Massachusetts Pesticide Certification needs to have worker protection training each year. I am offering several dates with a hybrid option (in-person or Zoom) for your workers to attend to cover this requirement. This will be a handler training and will allow workers to help apply general use pesticide and Roundup (glyphosate) or spot treat with Intensity or Stinger.  This training can be done with each person on a smartphone or computer, or in a group setting around a screen – but I need verification of each person attending.  Paperwork will be completed that can cover EPA WPS requirements.

Trainings will be held in the AD Makepeace Meeting Room, at the UMass Cranberry Station. To attend a training or for more information please contact Marty Sylvia martys[at]umass[dot]edu (martys[at]umass[dot]edu) or 508-265-6921.

2025 UMass Cranberry Pesticide Safety Meeting

• Wednesday, April 30, 2025
• 7:30 AM - 12:00 PM

• Early Registration fee is $60 per person (by 4/18/25)

• 4 pesticide credits are available

This will be a hybrid meeting; you can choose to join via Zoom or in-person. The meeting will be held in the AD Makepeace Meeting Room, at the UMass Cranberry Station. In-person seating may fill up fast due to room capacity allowance. Please return the meeting form as soon as possible to get your preferred attendance choice. 

TENTATIVE AGENDA

7:30 Check in starts, in-person coffee chat

7:45 Frost Update – Peter Jeranyama

8:00 WPS Requirements and Pesticide Safety – Marty Sylvia

8:25 Biopesticide Available in Cranberry – Crysta Taylor, Ocean Spray

8:50 Pesticide and Regulatory Updates – Katie Ghantous 

9:10 New Insects, Old Insects – Marty Sylvia

9:40 Keeping Quality Forecast & Optimizing Fruit Rot Fungicides– Leela Uppala

10:00 **Coffee Break**

10:15 Strategies Against Cranberry Fruit Rot, Upright Dieback & Phytophthora Root Rot– Leela Uppala

10:45 Herbicide Use Patterns – Katie Ghantous

11:15 Pesticide reminders: spray intervals, zone II, and restrictions! – Marty Sylvia

11:30 Chemigation - Brian McGrath, AD Makepeace

TO ATTEND THE 2025 UMASS CRANBERRY PESTICIDE SAFETY MEETING:

• Registration fee $60 per person (must be postmarked by 4/18/25)
• After 4/18/25 please contact Robyn Hardy by phone or email to register and cost will be $75 per person.

Please contact Robyn Hardy at 508-970-7635 or rmhardy[at]umass[dot]edu (rmhardy[at]umass[dot]edu). to have an email registration form sent to you to complete and return as soon as possible. In-person seating will go fast due to room capacity allowance. Once your form and payment are received, a confirmation email will be sent to each person confirming your selection of attendance via Zoom or in-person.  The Zoom confirmation email will have a link to register online. All meeting attendees MUST pay to attend whether receiving credits or not.