Cottonball 

Cottonball is caused by the fungus Monolinia oxycocci. The life cycle of this disease, which is called tip blight or hard rot in eastern Canada and eastern US, is similar to that of mummy berry of blueberry. It is caused by a closely related fungus. In the fall as cranberries ripen, those infected with cottonball remain waxy green. These berries contain a white cottony mass of fungus surrounding the seeds. The infected berries later turn brown and then black. The black mummies overwinter and in the spring produce apothecia which discharge spores just as new growth is starting. The spores infect the tips which later turn brown and wilt, becoming covered with a mass of greyish-brown spores just as blossoming commences. These spores infect the open flowers from which cottonball berries develop, thus completing the cycle.

Control

Remove and destroy infected fruits during harvest to prevent a build-up of disease inoculum.

For very susceptible varieties, such as Bergman, apply:

Topas 250E or Jade or Tilt (250 g/L propiconazole) at 500 mL/ha (200 mL/acre) or Mission 418 EC (418 g/L propiconazole) at 300 mL/ha (120 mL/acre) using a minimum of 200 L of water per hectare (80 L/acre). First application at or near flower bud swelling. Second application at leaf bud swelling (approx. 10–14 days later). Do not apply more than 4 times per year. Do not apply within 45 days of harvest.

Funginex 190 EC (190 g/L triforine) at 3 L/ha in 1000 to 1500 L of water (1.2 L/acre in 400 to 600 L of water) in the spring at leaf-bud break. Repeat 10 to 14 days later. Apply third spray at early bloom and repeat 10 to 14 days later. Thoroughly wet all buds and shoots. Do not apply more than 4 times per season. Do not re-enter treated fields within 48 hours of application. Do not apply within 60 days of harvest; or

Note: Funginex is not acceptable for U.S. and other markets. Check with your handler before using.

Quadris F (250 g/L azoxystrobin) at 1.0 L/ha (0.4 L/acre). Begin application at 5 to10 % bloom. Alternate with other fungicides on a 7 to 10 day schedule. Do not make more than 3 applications per year. Do not apply by air.  Do not apply within 30 days of harvest.

Note: Quadris is registered for suppression of cottonball only.

Fruit Rots

Several fungi cause pre- and post-harvest fruit rots of cranberry. The organisms that cause the rot are generally present in the beds and can cause the disease under adverse conditions. Symptoms vary, depending on the fungus, but usually consist of tan to black colourations on soft berries. Any abnormal change in colour or consistency of the berry during development is evidence of fruit rot. Externally, most of these rots are very similar and it usually requires laboratory culturing and identification from culture before the fungus causing the disease can be named.

The number of fungus species involved in fruit rot, each with a different life cycle, ensures that there are spores available for infection throughout most of the growing season. Where fruit rot was a problem the previous year, three sprays will be required to gain satisfactory control. Apply at 5% bloom, at 80% bloom or just after bloom.

Control

Apply as directed above:

Bravo 500 (500 g/L chlorothalonil) at 6.8 to 11.6 L/ha (2.7 to 4.7 L/acre). Apply at early bloom, late bloom and 10 to 14 days later. Use higher rate under severe conditions. Do not apply to fields when flooded or allow release of irrigation water for at least 3 days after application. Maximum of 3 applications per season. Do not re-enter treated areas within 48 hours of application. Do not apply within 50 days of harvest; or

Echo 720 (720 g/L chlorothalonil) at 4.7 to 8.1 L/ha (1.9 to 3.2 L/acre). Apply at early bloom, late bloom and 10 to 14 days later. Use the higher rate under severe conditions. Do not apply to fields when flooded or allow release of irrigation water for at least 3 days after application. Do not re-enter treated areas within 48 hours of application. Do not apply within 50 days of harvest; or

Quadris F (250 g/L azoxystrobin) at 1.0 L/ha (0.4 L/acre). Begin application at 5 to10 % bloom. Alternate with other fungicides on a 7 to 10 day schedule. Do not make more than 3 applications per year. Do not apply by air.  Do not apply within 30 days of harvest; or

Copper Spray, Copper Oxychloride 50 WP (50% copper oxychloride) at 4 kg/500 to 1000 L water/ha (1.6 kg/200 to 400 L water/acre). Apply at early bloom and repeat at 10 to 14 day intervals. Apply no more than 3 times per year. Ground application only. Do not re-enter treated fields within 48 hours of application. Do not apply within 2 days of harvest; or

Ferbam 76 WDG (76% Ferbam) at 6.75 kg/ha beginning at early bloom and repeat twice at 2 week intervals for a total of 3 applications. Do not apply within 28 days of mid-bloom.

Note: Ferbam is not acceptable to some markets. Check with your handler before using.

Red Leaf Spot 

Red leaf spot is caused by the fungus Exobasidium rostrupii. Glossy red spots which may coalesce to form large blotches appear on the upper leaf surface. Cream-coloured spores appear below the spots on the lower surface. Petioles and stems may be infected; they turn red and become enlarged. Secondary infection can cause damage to the tender new shoots. The terminal growth of uprights may be killed under heavy disease pressure, reducing the crop the following year. Berries are occasionally infected.  

This disease is not usually a problem on mature beds but often appears in young bogs where excessive growth has occurred due to high nitrogen availability. Shaded areas with poor air circulation may contribute to the disease. Fruit buds and blossoms injured by frost or insects are very susceptible. Symptoms may appear during a period of rainy, misty or cloudy weather at any time after growth has started in the spring.

Control

There are no fungicides registered for the control of this disease. The disease is rarely severe enough to warrant chemical control. However, the following cultural practices will help reduce the severity of infections:

Examine the nitrogen fertility program to avoid excessive growth in new beds.

Protect new growth from frost and insect damage.

Prevent growth of trees around edges of the bed as they may interfere with air circulation and create shade.

Red Shoot

Red shoot is caused by the fungus Exobasidium  perenne. This disease primarily infects dry pick fields. Infections appear on new growth in the spring. Infected shoots are stunted and have red, round-shaped leaves.  Leaves turn yellow or orange later in the season. Infected shoots become brittle.  This disease releaes spores in mid to late summer.  This disease is rarely of economic importance.

Rose Bloom

Rose bloom is caused by a fungus Exobasidium oxycocci. This disease is commonly seen in the spring, prior to bloom on buds that were infected the previous growing season.  Rose bloom infected shoots have abnormally thick swollen branches that are pale pink in colour.  These abnormal fleshy growths develop a whitish hue when close to spore release. Spore release occurs in May and June in Washington, and timing is likely similar in BC.  Rosebloom can reduce yield if not controlled.

Control

There are no fungicides registered for the control of rose bloom. However, fungicides applied for fruit rot will provide control of rose bloom if application timing coincides with spore release.

Upright Dieback and Twig Blights

Several fungi, including Phomopsis vacinii and some of those that cause fruit rots, cause upright dieback and twig blights on cranberry. Symptom expression depends on the fungus causing the disease. Some cause defoliation of runners and uprights combined with leaf reddening. Other twig blights may cause infected leaves to turn from a dark red to a bleached tan on dead uprights. The fungi may overwinter as mycelium in the young uprights where fruiting structures develop in the spring, or they may form black fruiting structures on the undersurface of dead leaves. In all cases, spores are released from these fruiting structures throughout the growing season. Control is based on the protection of new growth during the period of spore discharge. The same spray schedule used for fruit rot control will help to reduce damage from twig blight.

Control

Bravo 500 (500 g/L chlorothalonil) at 6.8 to 11.6 L/ha (2.7 to 4.7 L/acre). Apply at bud break, early bloom and late bloom. Use higher rate under severe conditions. Do not apply to fields when flooded or allow release of irrigation water for at least 3 days after application. Do not re-enter treated areas within 48 hours of application. Do not apply within 50 days of harvest; or

Echo 720 (720 g/L chlorothalonil) at 4.7 to 8.1 L/ha (1.9 to 3.2 L/acre). Apply at bud break, early bloom, and late bloom. Use the higher rate under severe conditions. Do not apply to fields when flooded or allow release of irrigation water for at least 3 days after application. Do not re-enter treated areas within 48 hours of application. Do not apply within 50 days of harvest; or

Copper Spray, Copper Oxychloride 50 WP (50% copper oxychloride) at 4 kg in 500 to 1000 L water/ha (1.6 kg/200 to 400 L water/acre). Apply at bud break, and repeat at 10 to 14 day intervals. Apply no more than three times per year. Ground application only. Do not re-enter treated fields within 48 hours of application.Do not apply within 2 days of harvest.