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Preventing Cranberry Diseases: How To Treat A Sick Cranberry Plant

Preventing Cranberry Diseases: How To Treat A Sick Cranberry Plant


By: Liz Baessler

Cranberries are a quintessentially American fruit that not many people even realize they can grow at home. If you’re one of the lucky few who have cranberries in their garden, odds are you’re very protective of them and their tart, delicious fruits. Keep reading to learn more about common diseases of cranberries and how to treat a sick cranberry plant.

Common Cranberry Diseases

Here are some of the most common diseases of cranberries:

Leaf spot – There are several bacterial and fungal issues that can cause leaf spots on cranberries. These include red leaf spot, Proventuria leaf spot, Cladosporium leaf spot, early leaf spot, and Pyrenobotrys leaf spot. These diseases thrive in moisture and can usually be prevented by irrigating during the day when water has time to evaporate and ensuring the soil drains well. If plants are already infested, treat with fungicide.

Red shoot disease – Early growth becomes spindly and turns red. While it looks strange, red shoot disease isn’t a serious problem and doesn’t have a definitive treatment.

Rose bloom – A fungus that causes some new growth to become thick and pink, like a rose. It can usually be prevented by increasing sun and air flow. It can be treated with fungicide.

Cottonball – The berries fill with a cottony fungus, and stem tips wither into a shepherd’s crook shape. The disease can be prevented by good drainage and by removing the previous year’s infected fruits.

Stem gall/canker – Shoots die back and growths develop on stems. Bacteria enter through wounds, so the disease can be prevented by avoiding winter and human damage. Sprays containing copper can be effective treatment if the infection isn’t bad.

Twig blight – Infected leaves turn dark brown then light tan and stay on the vine all through the winter. Twig blight can be prevented by encouraging good sun and air circulation and treated with fungicide.

Fruit rot – Many causes include bitter and blotch rot, early rot, hard rot, scald, and viscid rot. You can prevent this by making sure the vines don’t sit in water for too long. If you use flooding, only do it late in the season.

False blossom disease – Transmitted by the blunt-nosed leafhopper, the flowers of the plant grow erect and never form fruit. Apply insecticides if you notice a leafhopper infestation.

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Plant Pathology

Developing long-term, sustainable disease management approaches for the cranberry industry in MA is the major goal of the plant pathology program at the UMass Cranberry Station. An important focus area is addressing short- and medium- term disease-related needs identified by Massachusetts cranberry growers. To meet these objectives, our program focuses on research studies regarding ways to preserve fruit quality and into the development of related management practices adaptable to cranberry cropping systems in MA. Field research activities include fungicide efficacy and product screening trials, monitoring pathogen populations for fungicide resistance, and demonstration studies assessing the impact of cultural practices on disease severity. Other research efforts focus on improving diagnostic methods and studies that increase our understanding of the biology and population structure of cranberry pathogens.

Inaccurate plant disease diagnoses can lead to many more problems than just unnecessary applications and expenses. In fact, inaccurate diagnoses or inefficient diagnostic tools frequently result in severe yield losses if disease control measures are not implemented in a timely manner. One of the main services provided by the plant pathology program is access to field and lab diagnostics, with the purpose of helping cranberry growers identify plant health problems and providing them with the information necessary to develop a management approach that best fits their needs. In addition to providing information and services to growers, our program strives to assess and set research needs and priorities that incorporate the interests of all stakeholders in the cranberry industry.


Cranberry (Vaccinium macrocarpon)-Phytophthora Root and Runner Rot

Note the dying patches within this cranberry bed.

Photo by Jay W. Pscheidt, 1991.

Cause Although three Phytophthora spp. have been found in Oregon and Washington beds, P. cinnamomi is the most pathogenic. These fungus-like microorganisms have spores that swim to healthy plants, enter them, and destroy roots and runners under flooded conditions. Most beds with root rot were wet picked root rot in dry-picked beds occurs in areas with poor drainage.

Symptoms Dead spots in the bed occur first in poorly drained areas. Dead spots continue to expand to healthy areas. Plants at the margin may be stunted, usually have reddened foliage, and exhibit unthrifty growth. Lower (underground) runners have a red to olive-brown discoloration and lack feeder roots. Newly planted vines also die.

Cultural control Focus on these methods first.

  • Improve drainage in low areas of the bed.
  • Sand-in and replant poorly growing and low areas.
  • Uniform application of sprinkler irrigation will help avoid excessive water.
  • Maintain ditches and drains around the beds.
  • Construct new beds so that the crown is high enough to drain adequately into surrounding ditches or install internal drains.

Chemical control Use if needed but rotate materials from different groups to prevent or delay the occurrence of resistant fungi. Resistance to Group 4 fungicides has been detected in New Jersey.

  • Aliette WDG at 5 lb/A. Do not mix with surfactants or foliar fertilizers or use with copper products. Do not apply within 3 days of harvest. Do not use with adjuvants. Group P7 fungicide. 24-hr reentry.
  • Fosphite at 1 to 3 quarts/A. Do not use copper products within 20 days of treatment and do not use spray adjuvants. Group P7 fungicide. 4-hr reentry.
  • Fungi-Phite at 1 to 2 quarts/A. Group P7 fungicide. 4-hr reentry.
  • OxiPhos at 2.5 to 5 quarts/A as a foliar spray. Group P7 fungicide. 4-hr reentry.
  • Phostrol at 5 to 6 pints/A as a foliar spray. Do not apply within 3 days of harvest. Group P7 fungicide. 4-hr reentry.
  • ProPhyt at 4 pints/A. Group P7 fungicide. 4-hr reentry.
  • Rampart at 1 to 3 quarts/A. Group P7 fungicide. 4-hr reentry.
  • Ridomil Gold SL at 1 to 1.75 pints/A. Do not apply within 45 days of harvest. Apply first in fall after harvest, again in spring, and again 45 days before harvest. Use Ridomil Gold GR at 20 to 35 lb/A for spot treatment. Extend treated area 10 ft beyond the margin of weakened vines. Nontoxic to fish. Group 4 fungicide. 48-hr reentry.


Cooperative Extension: Cranberries

[An abnormal physiological condition believed to be due to an imbalance of nutrients in the plant usually due to water stress–from too much water or too little]

The following text is excerpted and adapted with permission from the UMass Extension’s Cranberry Station Newsletter — July 2004 issue (pp 1 – 2 — by Carolyn DeMoranville):

Maine cranberry leaves exhibiting Yellow Vine Syndrome compare with injury from Evital® herbicide where the yellow and green color pattern is reversed.

Yellow Vine (YV) shows up as a yellowing along the leaf margins (edges) with the areas along the leaf veins remaining green (see photos below). Usually the symptoms show up first in the old leaves and then move up the stem into the new growth. The most common time for the symptoms to become severe is around fruit set when demand for resources in the plants is high and dependence on sprinkler irrigation is greatest.

What causes Yellow Vine? The YV symptoms are most likely due to nutritional imbalances in the cranberry plants [potassium and magnesium in particular]. But fertilizer management is not the cause of the problem. Instead, we believe that the nutrient imbalance is secondary to root problems caused by stress. The stress involved is most often water stress (too much OR too little) but may also involve herbicide stress on some bogs. These stress conditions lead to poor root development. [Very wet conditions] can lead to shallow rooting. Casoron® use can aggravate the problem and it has often shown up in Maine cranberries where Casoron® was used.

C. Armstrong Yellow Vine Syndrome (Maine: 8/8/2016)

Massachusetts bogs with patches of YV have had soil water content in the YV areas that was either much higher or much lower than that in the surrounding green areas. The consistent finding has been that the rooting depth in YV areas is shallower than that in unaffected areas. In drought conditions, common most years during July and August, uneven distribution of water occurs due to reliance on sprinkler irrigation and varying distance to the underlying water table. Put this together with the high nutrient demand during early fruit development and nutritional problems may be the result. Fertilizer tends to be washed away from the roots during irrigation and areas with poor rooting may not be able to move enough minerals and water to meet the demands of both shoots and fruit. This sets up a competition for resources in which the developing fruit and the youngest leaves (at the top of the shoot) are the best competitors, leaving the older leaves showing symptoms of nutrient stress, in this case, YV.

Treating Yellow Vine (short-term fixes): YV plants are not doing well at taking in nutrients from the roots. For this reason, adding more fertilizer to the soil most likely will do little to arrest or reverse YV. Instead, foliar feeding should be considered. Providing nutrients through the leaves, bypassing the roots, can help to bring the plants back into nutritional balance. Based on tissue testing in YV bogs over a period of years, and based on field research and grower experiences, the most likely foliar feeds to be helpful are magnesium (Mg) and urea. These should be used separately. If you have had success with Mg in the past, try it first, otherwise try the urea first. Apply at dawn or dusk (preferred) as you would a pesticide (minimize washoff). The aim is to have the plant stay wet for several hours after the material is applied so that it may penetrate into the leaves. Use urea at 2-4 lb/A (to give approximately 1-2 lb/A nitrogen). For Mg applications, use a commercial foliar feed (3% Mg) at 1-2 qt/A or apply 2/3 lb/A Epsom Salts (magnesium sulfate). Urea and Epsom Salts should be dissolved in water prior to application as a foliar feed.

Treating Yellow Vine (long-term solutions): In the long term, changes in water management may be needed. In most cases, YV appears in areas that were too wet early in the season. This leads to limited root development and these same areas are then the most susceptible to YV and water stress later in the season. Rooting depth can be improved by keeping the bed well drained early in the season. This is particularly important in years with frequent frost nights requiring sprinkler operation or in years with heavy rainfall. When the water table is closer than about 6 inches below the surface, root development and root function is impaired. A float device, designed by Bruce Lampinen, mounted in a perforated pipe (directions for constructing and installing these are available from the Station) is useful to monitor the depth to the water table and to minimize times when the water table is too close to the root zone. Water can move up from a water table at a depth of up to about 15 inches by the process of ‘capillary rise’. With a water table below 15 inches, capillary rise may be unable to keep up with plant water demands, particularly at midday under stressful conditions (hot, dry, windy). A tensiometer can also be used to monitor moisture in the root zone. A water table varying from 6 to 15 inches in depth (as recommended above) will result in tensiometer readings between 1.5 cbar (at 6″ water table depth) to about 4 cbar (at 15″ water table depth). Therefore, tensiometer readings can be used to assess water status and irrigation can be scheduled based on an early morning reading of the tensiometer (see below). Ideally, irrigation water should be applied as a combination of subirrigation (manipulation of the water table) and overhead sprinkler irrigation.

Morning tensiometer readings:

  • 0 – 1.5 cbar soil is too wet
  • 1.5 – 4.0 cbar adequate water is available
  • 4.0 – 7.0 cbar adequate water for mild conditions, but if hot and/or dry conditions are forecast, irrigation should be applied
  • >8.0 cbar irrigation is needed, regardless of weather conditions


Cranberries squashed as folk remedy for urinary infections

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CHICAGO – Another folk remedy bites the dust. Cranberry capsules didn’t prevent or cure urinary infections in nursing home residents in a study challenging persistent unproven claims to the contrary.

The research adds to decades of conflicting evidence on whether cranberries in any form can prevent extremely common bacterial infections, especially in women. Many studies suggesting a benefit were based on weak science, but that hasn’t stopped marketers and even some health care providers from recommending cranberry juice or capsules as an inexpensive way to avoid these uncomfortable and potentially risky infections.

The new study , published online Thursday in the Journal of the American Medical Association, used rigorous methods and the results are convincing, according to a journal editorial. Health care providers who encourage using cranberry products as a prevention method “are doing their patients a disservice,” the editorial says.

Urinary infections lead to nearly 9 million doctor visits and more than 1 million hospitalizations each year. Men, because of their urinary anatomy, are less vulnerable, while almost half of all U.S. women will develop at least one of these infections in their lifetime. Symptoms can include painful, frequent urination and fatigue. Antibiotics are often used to treat the infections, which usually are not serious but can lead to kidney infections and sometimes dangerous bloodstream infections. Urinary infections are the most commonly diagnosed infection in nursing home residents, but they often have no obvious symptoms and evidence suggests antibiotics have little effect in these older patients without symptoms, the study authors say.

The research included 147 older women in nursing homes who were randomly assigned to take two cranberry capsules or dummy pills for a year. The number of women with laboratory evidence of infection — bacteria and white blood cells in their urine — varied during the study but averaged about 29 percent overall in both groups. Ten infections in the cranberry group caused overt symptoms, compared with 12 in the placebo group but that difference wasn’t statistically significant. There also were no differences in hospitalizations and deaths between the two groups. The National Institutes of Health helped pay for the research, led by Dr. Manisha Juthani-Mehta, a Yale University infectious disease specialist.

Ocean Spray Cranberries, Inc., one of the best-known makers of cranberry-based products, promotes the purported health benefits on its website. Responding to the new study, company spokeswoman Kellyanne Dignan cited previous studies that suggested a benefit and said, “We take great pride in our cranberry products and the health benefits associated with them.”

People who think they have a urinary infection should see a doctor for diagnosis and treatment, but avoid cranberry products “in place of proven treatments for infections,” according to the National Institutes of Health alternative medicine branch.

The journal editorial says additional research is needed to find effective treatments for nursing home residents and others.

“It is time to move on from cranberries,” the editorial says.

More on urinary infections online: http://tinyurl.com/hd3p3r3


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