Berries Production Guide

Blueberries
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Diseases

This section was updated - 13 June 2017

Rates of fungicides recommended are for mature blueberry plantings unless otherwise specified. Reduced amounts of spray volume should be applied for smaller, immature bushes. For small area applications refer to "Spray Calibration".

Alternaria Leaf Spot and Fruit Rot (Alternaria spp.)

Damage

Alternaria fungus can cause fruit rot and leaf spot. Leaf spot is not usually a serious problem except that leaf spots will produce spores during cold, wet periods which then can cause fruit infections.

Symptoms

Leaf spots are small (1 to 5 mm wide) and light brown to grey with a brownish red border. Infected fruit becomes soft with a flat, fuzzy greenish-black mould which contains many spores. Fruit can begin to rot before and after harvest.

Disease Cycle

The Alternaria fungus overwinters on the ground, on and in twigs, and on plant debris. Infected tissues produce spores during the spring which are transferred to fruit by wind and other means. Fruit infection may occur before harvest or during the post-harvest period.

Monitoring

During the spring, check for leaf infections if weather has been cool and wet. High levels of disease development on leaves may promote fruit infection. Watch the crop closely during harvest. If fruit infection was severe, watch for leaf symptoms the following spring.

Management

Cultural control

The most important control measure is to cool fruit rapidly after harvest. Do not let fruit become over-ripe. Minimize wounding or bruising during the harvesting operation.

Biological control

None.

Chemical control

Where Alternaria fruit rot has been a problem, apply at green tip, pink bud and petal fall:

Bravo 500 (500 g/L chlorothalonil)at 7.2 L/ha (2.9 L/acre) or Bravo 720 or Echo 720 (720 g/L chlorothalonil) at 5.0 L/ha (2.0 L/acre). Apply in 1000 L/ha (400 L/acre) of water. If the bushes are small, reduce spray volume appropriately. Do not re-enter treated areas within 48 hours of application. Do not apply within 54 days of harvest

For control of alternaria leaf spot, apply at green tip, pink bud and petal fall:

Inspire Super (86 g/L difenoconazole, 249 g/L cyprodinil) at 836 to 1475 ml/ha (338 to 597 ml/acre). Apply in a minimum of 200 L/ha (81 L/acre) of water. Do not apply more than two consecutive treatments of Inspire Super before alternating with another fungicide with a different mode of action.  Do not use more than 5.9 L/ha (2.4 L/acre) per crop per season.  Do not apply within 1 day of harvest.

Other fungicides registered for Mummy Berry, Anthracnose and Botrytis fruit rot (below) will help protect against Alternaria.

Anthracnose (Colletotrichum acutatum)

Damage

Anthracnose is present at low to moderate levels in all blueberry production areas in BC, but not on all farms. Under warm and wet conditions, the fungus causes primarily pre- and post-harvest fruit rot, but can also cause shoot and blossom blight and stem canker. The fungus often spreads from infected berries to healthy berries during and after harvest leading to significant post harvest losses.

Symptoms

On berries, infected areas initially appear as soft, sunken spots near the calyx (blossom)-end of the fruit. As the disease progresses, the fungus produces salmon to orange coloured masses of spores on sunken fruit surfaces which become more apparent on harvested fruits. Heavy infections on flower buds and young twigs can cause shoots and blossoms to turn brown to black colour. Stem cankers are rare, but brown to black sunken lesions of 1/8” in diameter with raised margins can appear on stems under favourable conditions.

Disease Cycle

The pathogen Colletotrichum acutatum over winters in or on live twigs and flower buds, and also on dead twigs, spurs and fruit trusses. In the spring, the fungus produces spores which get splashed onto flowers and developing fruits mainly by rain and overhead irrigation. At least twelve hours of continuous leaf wetness at temperatures between 12 to 27o C is required for new infections to occur. Some infection may also occur at cooler temperatures. Infected young shoots and blossoms may show blight and die-back like symptoms. Berries are susceptible to infection at all stages in their development. The fungus remains dormant on the developing berries until berries begin to ripen. Spent fruit trusses can be infected after harvest.

Monitoring

Watch the crop during harvest for symptoms of the disease.

Management

Cultural control

Prune to allow good air movement. This speeds up the drying of plants after a rainfall.

Where possible, avoid overhead irrigation. If using overhead irrigation, sprinkle in the early morning so plants dry during the day.

Cool fruit as soon as possible after harvest and store at cool temperatures to slow down rot.

Spores can be spread on totes, flats and harvesting machines. Where possible, avoid introducing anthracnose to the farm through infested totes and flats. Do not take a harvester from an infected field to a healthy field.

Chemical control

Where anthracnose has been a problem, apply:

Group M

Bravo 500 (500 g/L chlorothalonil) at 7.2 L/ha (2.9 L/acre) or Bravo 720 or Echo 720 (720 g/L chlorothalonil) at 5.0 L/ha (2.0 L/acre). Apply at petal fall. In unusually mild springs, apply at green tip and pink bud also. Apply in 1000 L/ha (400 L/acre) of water. If the bushes are small, reduce spray volume appropriately. Do not re-enter treated areas within 48 hours of application. Do not apply within 54 days of harvest; or

Group U

Aliette WDG (80% fosetyl-Al) at 5.6 kg/ha (2.2 kg/acre) in 300 to 1000 L/ha (120 to 400 L/acre) of water. Begin sprays at the pink bud stage and continue on a 14 to 21 day interval. Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply more than 4 times per year. Do not apply within 1 day of harvest; or

Confine Extra (53% mono and di-potassium salts of phosphorous acid) at 4.0 to 5.0 L/ha (1.6 to 2.0 L/acre) in enough water to provide coverage. Begin sprays when conditions are favourable for disease and continue on a 7 to 21 day interval. Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply more than 5 times per year. Do not apply within 1 day of harvest; or

Group 3

Quash (50% metconazole) at 180 g/ha (72 g/acre) in enough water to obtain good coverage. Apply at bloom.  Do not apply more than 3 times per year. Do not make more than 2 sequential applications. Do not apply more than 540 g/ha (216 g/acre) per season. Do not apply within 7 days of harvest; or

Group 3/ Group 9

Inspire Super (86 g/L difenoconazole, 249 g/L cyprodinil) at 1161 to 1475 ml/ha (470 to 597 ml/acre) in early bloom. A second application can be made 7 to 10 days later. Apply in a minimum of 200 L/ha (81 L/acre) of water. Do not apply more than two consecutive treatments of Inspire Super before alternating with another fungicide with a different mode of action.  Do not use more than 5.9 L/ha (2.4 L/acre) per crop per season.  Do not apply within 1 day of harvest; or

Group 3/ Group 11

Quilt (125 g/L propiconazole, 75 g/L azoxystrobin) at 1.0 L/ha (0.4 L/acre) in enough water to obtain good coverage. Do not apply more than 3 times per season. Do not apply within 30 days of harvest; or

Group 7/11

Pristine WG (25.2 % boscalid, 12.8 % pyraclostrobin) at 1.3 to 1.6 kg/ha (0.52 to 0.64 kg/acre) in enough water to obtain good coverage. Apply at full bloom through fruit development. Sprays should be timed to provide protection when conditions are wet and average temperatures are over 15oC. Use the shorter interval when disease pressure is high. Do not apply more than 4 times per crop per season. Do not apply Pristine or other products containing Group 7 or 11 fungicides more than twice in succession. Do not re-enter treated fields for hand harvesting within 1 day of application. If mechanical harvesting, application can be made up to the day of harvest; or

Group 11

Cabrio EG (20% pyraclostrobin) at 1.0 kg/ha (400 g/acre) in enough water (up to 1000 L/ha) to get good coverage. Apply beginning at full bloom and continue through early fruit development. Sprays should be timed to provide protection when conditions are wet and average temperatures are over 15°C. Do not apply more than 4 times per season. Allow at least 10-14 days between applications. Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply within 1 day of harvest; or

Group 9/12

Switch 62.5 WG (37.5% cyprodinil and 25% fludioxinil) at 775 to 975 g/ha (310 to 390 g/acre) in enough water to obtain good coverage (500 to 1000 L/ha (200 to 400 L/acre)). Sprays should be timed to provide protection when conditions are wet and average temperatures are over 15oC. Do not apply Switch more than twice in succession. Alternate with fungicides from other groups. Do not apply within 1 day of harvest; or

Group 29

Allegro 500 (40% fluazinam) at 2.24 L/ha in 300 to 1000 L of water (0.9 L/acre in 120 to 400 L of water). Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply more than 4 times per season. Do not apply within 30 days of harvest.

Armillaria Root Rot (Armillaria spp.)

Damage

Root rot caused by the fungus, Armillaria, is not widespread in BC blueberry fields, but in recent years the incidence has increased. It can cause substantial damage to blueberries.

Symptoms

Plants infected with Armillaria can express a range of symptoms, depending on the age and vigour of the plant and soil conditions. Generally, symptoms are slow to develop and can take a few years to express. Plants may show initial symptoms of nutrient deficiency followed by a gradual decline/dieback over several years. Affected plants tend to have small, chlorotic leaves and produce less fruit. Severely infected plants lose vigour, wilt and die. Infection may confined to a localized area or randomly spread throughout the field, depending on the distribution of the pathogen in the soil.

Disease Cycle

Armillaria is known to infect nearly five hundred plant species, mostly woody perennials. The fungus is most likely to be present in fields that are adjacent to wooded areas or have recently been cleared. Armillaria survives as mycelial strands or shoestring-like structures called “rhizomorphs” and thrives on organic debris and decaying roots and stumps. Infection of blueberry roots occurs, primarily, when roots come in contact with rhizomorphs. Further spread of the fungus between infected and healthy plants is by root-to-root contact. If the infection is confined to the roots plants show gradual decline over several years. However, if the fungus girdles the crown, then decline and death is rapid.

Monitoring

In late spring and summer, look for early symptoms of nutrient deficiency and reduced plant vigour. The growth of Armillaria is often visible as pale-yellow or white, thread-like mycelium and/or dark-brown to black rhizomorphs beneath the bark of the infected roots and base of the stem or trunk region. In late summer and fall, if conditions are favourable, the fungus may produce yellowish brown mushrooms at the base of the affected plants.

Management

Cultural control

Newly cleared fields selected for blueberry planting should be thoroughly worked and all stumps, root pieces and decaying wood materials removed. Newly cleared fields should be left fallow for at least two to three years or cropped to annual non-host crops to reduce the inoculum of the fungus. Soil fumigation can be used to further reduce or eliminate the fungus. Fungal inoculum found in the deeper soil may not be killed by fumigation.

In established fields, infected plants, including the trunk and all roots should be removed and burned. Examine all adjacent healthy plants and remove them if infected or suspected of infection. Soil fumigation of the infected area helps to reduce the inoculum and spread of the fungus. Avoid using sawdust mulch in and around infected area.

Biological control

None.

Chemical control

None.

Bacterial Blight (Pseudomonas syringae pv syringae)

Damage

This disease can be damaging under cool, wet conditions. Severely infected flower buds and canes can reduce yields. Young plants may be killed if lesions are extensive. Frost and winter injury on plant tissues encourages bacterial entry into plants and increases blight severity.

Symptoms

Symptoms first appear in late winter on young canes as water-soaked lesions. These lesions develop into irregular brownish-black areas up to a few millimeters long which can expand to the entire length of one-year-old canes. Buds found within these lesions on infected canes are killed and stems may become girdled. Flower buds may be killed before they fully open. Spring frosts often accelerate bacterial blight incidence and severity. The disease also attacks young plants and cuttings in propagation beds.

Disease Cycle

This disease is caused by the bacterium Pseudomonas syringae pv. syringae. The bacterium lives on plant surfaces, e.g. stems and buds, but it can only cause damage after it gains entry into the plant. It enters through natural openings, wounds, and frost- and winter-damaged tissues. Once the bacterium gains entry, under favourable conditions, it multiplies and spreads internally. Most strains of this bacterium kill plant tissues by producing plant toxins. At below freezing temperatures, the bacterium also produces a protein which triggers ice nucleation resulting in freezing damage to plant tissues. Freeze damaged tissue can be more prone to secondary infection.

Monitoring

Look for symptoms of the disease during pruning to determine if fall copper sprays will be required.

Management

Cultural control

Prune out and remove diseased wood, especially before fall rains, to reduce the chance of new infections.

Apply the appropriate amount of nitrogen based on tissue test results. Over-fertilization or N applications after mid-July can cause overly vigorous growth which is very susceptible to fall infection.

The varieties Duke, Bluecrop, Patriot, Brigitta, Jersey and Bluetta are susceptible. Elliott, Rancocas and June have shown some resistance. Bluecrop, Patriot, Brigitta and 1613A appear to be more susceptible to blossom blight than others.

Biological control

None.

Chemical control

Copper Oxychloride 50 or Copper Spray Fungicide (50% copper oxyehloride). Apply at 2 to 4 kg with a spreader sticker in 500 to 1000 L water per hectare (0.8 to 1.6 kg in 200 to 400 L water per acre). Apply the high rate (4 kg) once before fall rains and again at 50% leaf fall. In the spring, apply the low rate (2 kg) at bud burst and at two week intervals if the weather is cool and wet (maximum of 6 applications per year). For backpack sprayers, use 20 to 40 g of Copper oxychloride WP in 10 L water. Do not re-enter treated fields within 48 hours of application. Do not apply within 2 days of harvest.

Note: Surveys in 2000 and 2001 have shown that copper tolerant strains of the bacterium exist in some fields. Copper applications to fields with tolerant bacteria will increase copper tolerant populations which may result in higher disease levels. Higher copper rates will not provide better control and will increase the risk of plant damage in the spring. Repeated copper applications over time will continue to select for more copper tolerant strains in the field. Alternatives to copper are being explored.

Note: Copper can damage new spring foliage. Use the lower rate for spring applications and apply under fast drying conditions to reduce the risk of plant injury. Avoid application on cool, cloudy days; or

Bordeaux Mixture (8-8-100). Apply twice in the fall, once before fall rains (about Oct. 1) and again one month later. Refer to “Bordeaux Mixture” in General Pests for formula and mixing directions. Copper is the active ingredient in Bordeaux so copper tolerance comments above apply to it also; or

Cueva (Copper ocanoate 1.8%) use a 0.5 % to 2% solution, applied at 470-940 L/ha (188-377 L/acre).Apply at the start of flowering and continue every 7 to 10 days. Do not apply within 1 day of harvest, or

Serenade Opti (QST 713 strain-Bacillus subtilis) at 0.6 to 1.7 kg/ha (0.24 to 0.68 kg/acre) . Apply before fall rains and again during dormancy before spring.  Use enough water to obtain thorough coverage. Serenade may be applied up to and including the day of harvest.

Note: Serenade is a bacterial-based biofungicide. It is approved for organic production.

Serenade Max: no longer produce.

Botrytis Blight and Fruit Rot (Botrytis cinerea)

Damage

The fungus Botrytis occasionally causes significant losses especially if wet weather occurs during bloom, fruit ripening or harvest. Infected fruit often does not develop symptoms until after harvest which creates dissatisfaction with retailers and consumers.

Symptoms

Botrytis infected twigs appear grey and dried-up. Grey, fuzzy growth can be seen on infected twigs. Infected blossoms turn brown and dried-up and may resemble symptoms of blueberry scorch or bacterial blight.

Fruit rot symptoms often are not visible until after harvest when the distinctive grey, fuzzy growth develops. Healthy berries next to infected ones quickly become infected. With prolonged wet weather after bloom, old flowers can remain attached to developing berries. Then Botrytis may infect developing berries through the flower tissue. These berries develop purplish, sunken areas where the old flower has stuck. Infected berries usually do not mature.

Disease Cycle

Botrytis is a very common fungus. It cannot be eliminated from fields, only reduced. The fungus overwinters on branch tips, and on dead plants or organic debris on the ground. In the spring, masses of spores are produced on this material and carried by wind currents to new blueberry growth. Blossoms, twigs and fruit can be infected under periods of high relative humidity (>95%) and cool temperatures (15-20°C). Twigs damaged by cold are more susceptible to infection. The fungus enters through blossoms and may remain in a dormant state until the fruit is harvested. The fungus produces numerous spores on infected twigs, blossoms and pre- and post-harvested fruits.

Monitoring

Examine twigs for symptoms of Botrytis infection. Alert workers to symptoms of twig infection and attempt to prune these out where possible.

Watch for infection of blossoms.

Management

Cultural control

Improve air movement in the plant canopy through selective pruning. Avoid high levels of nitrogen which promotes excessive leaf growth. Carefully time overhead irrigation so plants can dry as quickly as possible. Early morning applications are preferred. Cool fruit as quickly as possible after harvest.

Biological control

None.

Chemical control

To guard against losses from fruit rot, protect the blooms with sprays applied at the start of blossom. Repeat sprays in 7 to 10 days and, if necessary, during fruit ripening. To delay development of resistance rotate sprays from the different groups listed below.

Apply:

Group M

Captan 80 WDG (80% captan) at 2.0 kg/1000 L of water/ha (0.8 kg in 400 L/acre). Do not re-enter treated fields within 72 hours of application unless protective clothing is worn. For hand harvesting, do not apply within 3 days of harvest. For machine harvest, do not apply within 2 days of harvest; or

Captan 50 WP (50% captan) at 3.6 kg/1000 L of water/ha (1.44 kg in 400 L/acre). Do not re-enter treated fields within 72 hours of application unless protective clothing is worn. For hand harvesting, do not apply within 3 days of harvest. For machine harvest, do not apply within 2 days of harvest; or

Maestro 80 DF (80% captan) at 2.25 kg/1000 L of water/ha (0.9 kg in 400 L/acre). Do not re-enter treated fields within 72 hours of application unless protective clothing is worn. For hand harvesting, do not apply within 3 days of harvest. For machine harvest, do not apply within 2 days of harvest;or

Ferbam 76 WDG (76% Ferbam) at 3.75 kg/1000 L of water may be applied from when flower buds break to mid-bloom. Use enough spray volume for thorough coverage. Do not apply within 40 days of harvest; or

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

Group 3/ Group 9

Inspire Super (86 g/L difenoconazole, 249 g/L cyprodinil) at 1033 to 1475 ml/ha (418 to 597 ml/acre). Apply in a minimum of 200 L/ha (81 L/acre) of water.  Begin applications in early bloom or when condiitions are conducive to Botrytis. A second application can be made 10 to 21 day later. Do not make more than two applications per crop per season for Botrytis. Do not apply within 1 day of harvest; or

Group 7

Kenja 400SC (400g/L Isofetamid) at 1 to 1.24  g/ha (0.4 to 0.5 g/acre). Begin applications in early bloom or when condiitions are conducive to Botrytis. Spray on a 7 to 14 days interval. Do not use more than 2 consecutive applications of isofetamid or other group 7 fungicide. Do not use more than 5 applications per year, or

Lance WDG or Cantus WDG (70% boscalid) at 560 g/ha (224 g/acre) in enough water to obtain good coverage. Apply beginning at early bloom. Spray in rotation with fungicides from other groups on a 7 to 14 day schedule. Use the shorter interval when disease pressure is high. Do not apply more than 4 times per crop per season. Do not apply Lance, Cantus or other Group 7 fungicides more than twice in succession. Lance or Cantus can be applied up to the day of harvest; or

Sercadis (300 g/L fluxapyroxad) at 250-666 mL/ha (100-266 mL/acre) in enough water to obtain good coverage.  Apply beginning at early bloom, prior to onset of disease development. Spray in rotation with fungicides from other groups on a 7 to 14 day schedule.  Use the shorter spray interval when disease pressure is high. Do not apply more than 3 times per crop season. Can be applied up until the day of harvest; or

Note: Sercadis will only provide suppression of Botrytis 

Group 7/9

Luna Tranquility (125 g/L fluopyram, 375 g/L pyrimethanil) at 1200 ml/ha (486 ml/acre) in a minimum of 500 L/ha (202 L/acre) of water. Begin applications in early bloom or when conditions are conducive to Botrytis and repeat as required at 7 to 10 day intervals.  Do not apply more than twice per crop per season for Botrytis.  Can be applied up until the day of harvest; or

Group 7/11

Pristine WG (25.2 % boscalid, 12.8 % pyraclostrobin) at 1.3 to 1.6 kg/ha (0.52 to 0.64 kg/acre) in enough water to obtain good coverage. Apply beginning at early bloom. Spray in rotation with other fungicides on a 7 to 14 day schedule. Use the shorter interval when disease pressure is high. Do not apply more than 4 times per crop per season. Do not apply Pristine or other products containing Group 7 or 11 fungicides more than twice in succession. Do not re-enter treated fields for hand harvesting within 1 day of application. Do not enter fields for all other activities until residues have dried. If mechanical harvesting, application can be made up to the day of harvest; or

Group 9

Scala (400g/L pyrimethanil) at 2.0 l/ha (0.78 l/acre) in a minimum spray volume of 1000 l/ha (393 l/acre). Make the first application at early flowering and repeat applications as required at 7-10 day intervals. Do not apply more than 2 times per crop per season.  Application can be made up to the day of harvest; or

Group 9, Group 12

Switch 62.5 WG (37.5% cyprodinil and 25% fludioxinil) at 775 to 975 g/ha (310 to 390 g/acre) in enough water to obtain good coverage (500 to 1000 L/ha (200 to 400 L/acre)). Apply when conditions are favourable for disease development. Do not apply Switch more than twice in succession. Alternate with fungicides from other groups. Do not apply within 1 day of harvest; or

Group 17

Elevate 50 WDG (50% fenhexamid) at 1.7 kg/ha (0.7 kg/acre) in enough water (up to 1000 L/ha) to obtain good coverage. Apply up to 4 times per season beginning at early bloom. Do not make more than two consecutive applications of Elevate. Do not apply within 1 day of harvest; or

BioFungicides

Serenade Opti (QST 713 strain-Bacillus subtilis) at 1.7 to 3.3 kg/ha (0.68 to 1.32 kg/acre). Begin applications at early bloom when conditions favour disease development. Repeat as necessary on a 7-10 day interval. Serenade may be applied up to and including the day of harvest; or

Note: Serenade is approved for organic production.

Serenade Max : no longer produced.

Regalia Maxx (20% extract of R. sachalinensis) at  0.125 - .0.25% v/v in 400 to 800 L/ha (160 to 320 L/acre) of water. Begin applications at early bloom when conditions favour disease and repeat at 7 to 10 day intervals. Regalia Maxx may be applied up to and including the day of harvest; or

Note: Serenade and Regalia Maxx are bacterial-based biofungicides.  They  will only provide suppression of fruit rot.

Timorex Gold (23.8% tea tree oil) at 1.5 to 2.0 L/ha (0.6 to 0.8 L/acre) in 400 to 800 L/ha (160 to 320 L/acre) of water.  For preventative treatments, apply at 7 to 14 day intervals. Avoid spraying in the heat of the day or when temperatures are above 35ºC. Do not apply within 2 days of harvest.

 

Crown Gall (Agrobacterium tumefaciens)

Damage

This disease is usually of minor importance but can be an issue in the nursery.

Symptoms

It is characterized by the presence of dark brown, rough galls on the roots, crown, stems and branches. The galls are normally round but they may appear as elongated structures on branches where several galls have grown together. Stems may be girdled by crown gall. Leaves above the infection may turn red and look similar to Godronia canker “flags”. Symptom development is often worse following winters where cold injury has occurred.

roots

Disease Cycle

Crown gall is caused by a bacterium. It is introduced into the plant as infected cuttings or through wounding. A common method of introduction is on infested pruning shears.

Monitoring

Look for swellings at the crown or along the branches. Use fluorescent tape to identify infected plants, and show pruners how to reduce the risk of contaminating healthy plants after working on infected ones.

Management

Cultural control

Obtain clean nursery stock.

If galls are found on established bushes, prune out and destroy infected stems. Take precautions to avoid spreading the disease on the pruning shears. Disinfect pruning shears after each cut by dipping them in a solution of 5% Virkon, Chemprocide or CleanGrow (16 mL/L) or a 1:10 dilution of household bleach. Caution, bleach will corrode metal. Make fresh solutions frequently as the pruning shears will not be disinfected if the water is dirty.

Control weevils as the crown gall organism can enter the blueberry plants through weevil feeding wounds.

Biological control (pre-plant only)

Dygall is a formulation of a naturally occurring bacterium that attacks the crown gall bacterium. It is applied to cuttings or plant roots before planting in infested soils. Dygall may be ordered from Mori Nurseries Ltd. in Ontario (416) 468-3218. Only trained nursery personnel should use this product.

Chemical control

There are no chemical controls.

Godronia Canker (Godronia cassandrae or Fusicoccum purifaciens)

Damage

Godronia or Fusicoccum canker is the most serious canker disease of blueberry in BC. Disease incidence seems to be increasing in recent years. Branches on affected plants are killed, reducing yields. Plants will die if too many branches are killed.

Symptoms

The leaves of infected branches turn a bright reddish-brown. These so called “flags” clearly stand out, even from a considerable distance, during the growing season.

Disease Cycle

The Godronia fungus overwinters as mycelium in living stems and crowns of infected plants. Small, black dots (pycnidia) that contain spores develop on the previous season’s cankers. The spores are released in wet weather and spread by water. Spores are released from early March to October but most infections occur during wet conditions in spring and fall. Infections usually begin at leaf scars and axils of leaf and flower buds, but may also occur at other openings in the bark. Cankers first appear as small, reddish discolourations on the stem. As the cankers enlarge, the centres usually become grey and the margins develop a reddish or dark brown colour. The cankers eventually girdle the stem, causing wilting and sudden death. Dead leaves turn a bright reddish-brown and remain attached. This symptom is called the “flag”.

Monitoring

It may take two or more years for complete girdling of the cane to occur. The “flag” in any given year may be the result of infections from several years ago – a point to consider when evaluating the effectiveness of control measures. Infected branches should be pruned out when first observed. Inform pruners of symptoms.

Management

Cultural control

Prune out and remove all diseased branches.

Prune to promote good air movement around plants.

Try to avoid overhead irrigation in fields with Godronia canker. If overhead irrigation is used, try to schedule irrigation periods early in the morning so plants can dry as quickly as possible.

Duke, Earliblue and Bluecrop are highly susceptible to this disease. The effect on Duke may be more severe as it is slow to produce replacement shoots from the crown. Rubel and Rancocas are resistant.

Biological control

None.

Chemical control

There are no fungicides registered for control. Fungicides applied for mummy berry, fruit rot and other diseases may help reduce Godronia infections.

Mummy Berry (Monilinia vaccinii-corymbosi)

Damage

This fungal disease is a serious disease of blueberries in south-coastal BC. Yield losses can be large if the disease pressure is high and the spring is wet. All varieties are susceptible to mummy berry but they differ in susceptibility to the primary and secondary disease stages.

Symptoms

Spring symptoms. Developing leaf shoots and flower clusters suddenly droop. Within 24 hours, the upper sides of these shoots and the veins in the leaves turn brown, and then develop a tan-grey fuzz. Secondary spores are produced in the fuzzy area. Bees are attracted by the sugars produced there and spread the secondary fungal spores to flowers. Affected leaves, shoots and flowers eventually fall off the plant. No further symptoms are seen until the berries start to ripen.

Berry symptoms. Infected berries turn cream to pink and then tan or whitish grey just before they start to ripen. White cottony mycelium can been seen when the berry is cut in half. The infected berries usually shrivel, harden, become pumpkin shaped and fall off the bush before harvest.

mummy berry

Disease Cycle

Primary infection. Mummies — the hard, black, pumpkin-shaped form that contain the fungus inside can live for several years in or on the soil. The fungus requires a chilling period during the winter before they can start to produce the trumpet-shaped cups (spore-producing structures called apothecia) in the spring. In late February to March, small cups grow from the mummies and produce spores (ascospores). These are ejected into the air about the time the buds start to open. The spores infect opening vegetative and flower buds. This stage is called the primary infection. Mummies buried 2.5 cm or more in the ground will not develop spores because the sprout-like structure (stipe) that grows from the mummy must be exposed to light before it can mature into an apothecium. Spores are only produced in the cup (apothecium).

Secondary infection. Infected buds become watersoaked, wilt and turn brown. A second type of spores (conidiospores) form on the diseased shoots about 3 weeks after the primary infection. These secondary spores are carried by the wind, water and pollinating bees to healthy flowers. The spores germinate and grow into the base of the flower where the berry will develop. This stage is the secondary infection. Infected berries develop normally until they near maturity. Before harvest, infected berries eventually turn whitish grey, and fall to the ground. Eventually the outside part of the berry decays and the black, pumpkin-shaped berry with fungus within remains on the soil surface.

Monitoring

Starting in mid-February monitor for bud development. Time fungicide applications according to plant growth stage. Start to apply fungicides when 5 mm of green tissue is showing on the leaf buds or when the bud scales are showing on the flower buds. Infection cannot occur before the buds have reached this stage. Continue protective sprays for primary infections until leaf buds start to unroll.

Keep a close watch for the development of primary infections. If seen, apply 1 to 2 additional sprays to protect the opening blossoms from secondary infections. This stage usually occurs between late April and late May depending upon the variety and growing conditions.
 

Caution: Fruit russeting has been observed when Funginex is applied during 50-80% bloom. These later sprays are not necessary if primary infections are prevented. Therefore, it is extremely important to prevent berry infections by monitoring the field for the development of the plant buds.

Management

Cultural control

Anything that damages the mummies or the developing apothecia will reduce mummy berry infections. In fields that do not have permanent cover crops between the rows and/or sawdust mulch, mummies may be raked between the rows in early spring. Rotovating or frequent harrowing after raking will bury mummies and destroy developing apothecia. Disease development is usually most severe in low-lying, moist areas, or beside windbreaks where air circulation is poor.

Biological control

None.

Chemical control

Timing of fungicide sprays is critical for successful mummy berry control. It is especially important to protect the buds from primary infections. To prevent primary infections, apply the first spray when 5 mm of green tissue is showing on developing leaf buds or when the bud scales are exposed on the flower buds. This usually occurs in March but varies with location and weather conditions. Repeat the spray in 10 to 14 days. If wet weather continues, a third spray in another 10 to 14 days may be required. These sprays protect the buds but do not kill the apothecia on the ground.

Apply:

Group 3

Funginex DC (190 g/L triforine) at 3 L/1000 L of water/ha (1.2 L/400 L of water/acre) Thoroughly wet the bushes including all buds and shoots. Do not re-enter treated fields within 48 hours of application. Do not apply within 60 days of harvest; or

Topas 250E or Jade or Tilt (250 g/L propiconazole) at 500 mL/ha (200 mL/acre) or Mission 418 EC or Bumper (418 g/L propiconazole) at 300 mL/ha (120 ml/acre) using a minimum of 200 L of water per hectare (80 L/acre). Do not use more than 4 applications per year. Do not re-enter treated fields for pruning within 5 days of application. Do not apply within 60 days of harvest; or

Quash (50% metconazole) at 180 g/ha (72 g/acre) in enough water to obtain good coverage. Do not apply more than 3 times per year. Do not make more than 2 sequential applications. Do not apply more than 540 g/ha (216 g/acre) per season. Do not apply within 7 days of harvest; or

Proline 480 SC (480 g/L prothioconazole) at 315 to 420 mL/ha (126 to 168 mL/acre) in enough water to obtain good coverage. Do not apply more than twice per year. Do not apply more than 820 mL/ha (328 mL/acre) per crop per year. Do not apply within 7 days of harvest; or

Indar (75% fenbuconazole) at 140 g/ha (56 g/acre) in enough water to obtain good coverage. Do not apply more than 4 times per season. Do not apply within 30 days of harvest; or

Group 3/ Group 9

Inspire Super (86 g/L difenoconazole, 249 g/L cyprodinil) at 558 to 836 ml/ha (226-338 ml/acre) starting at flower bud swelling.  Apply in a minimum of 200 L/ha (81 L/acre) of water. Additional applications can be made at leaf bud  swelling, pink bloom and early bloom.  Do not make more than four applications a year.  Do not apply within 1 day of harvest; or

Group 3/Group 11

Quilt (125 g/L propiconazole, 75 g/L azoxystrobin) at 1.0 L/ha (0.4 L/acre) in enough water to obtain good coverage. Do not apply more than 4 times per season. Do not apply within 30 days of harvest; or

Group 29

Allegro 500 (40% fluazinam) at 2.24 L/ha in 300 to 1000 L of water (0.9 L/acre in 120 to 400 L of water). Do not apply more than 4 times per season. Do not apply within 30 days of harvest; or

Note: Allegro only provides suppression of mummy berry.

BioFungicides

Serenade Opti (QST 713 strain-Bacillus subtilis) at 2.0 to 3.3 kg/ha (0.8 to 1.32 kg/acre). Begin applications at bud break and repeat on a 7-14 day interval. Serenade may be applied up to and including the day of harvest; or

Note: Serenade is approved for organic production.

Serenade Max: no longer produced.

Regalia Maxx (20% extract of R. sachalinensis) at  0.125 - .0.25% v/v in 400 to 800 L/ha (160 to 320 L/acre) of water. Begin applications at bud break and repeat at 7 to 10 day intervals. Regalia Maxx may be applied up to and including the day of harvest; or

Actinovate (0.0371% Streptomyces lydicus) at 425 to 840 g/ha (172 to 340 g/acre) in 200 to 1400 L/ha (80 to 566 L/acre) of water to obtain uniform coverage.  Begin applications when conditions are conducive to disease development and repeat every 7 to 14 days.  Apply spray within 4 hours of mixing.

Note: Serenade, Regalia Maxx and Actinovate are bacterial-based biofungicide.  They will only provide suppression of mummy berry.

Phomopsis Canker (Phomopsis vaccinii)

Damage

A serious disease in eastern highbush blueberry growing regions which is becoming more prevalent in BC blueberry fields. When cankers are found, they are often associated with bushes that were wounded or growing under stressful conditions.

Symptoms

Cankers develop on one-, two- and three-year old stems. Cankers on one-year old stems are 5 to 15 cm long—much longer than young Godronia cankers. Older cankers on two- and three-year old stems are grey and somewhat flattened. When the canker girdles the stem, the leaves turn red and remain attached to the stem. The appearance is similar to Godronia canker “flags”.

Disease Cycle

The fungus overwinters inside infected stems and produces spores in the spring. Spore release is triggered by rainfall and may occur from blossom bud swell until late August. Wounded plants are more susceptible to infection.

Monitoring

Watch for the appearance of “flags” during the summer.

Management

Biological Control

None.

Cultural Control

Prune out infected branches by cutting as deep into the crown as possible. Destroy prunings.

Promote good air movement by pruning and controlling weeds.

Chemical Control

Apply:
Group M

Bravo 500 (500 g/L chlorothalonil) at 7.2 L/ha (2.9 L/acre). Apply before disease development. Do not re-enter treated areas within 48 hours of application. Do not apply within 54 days of harvest; or

Bravo 720 or Echo 720 (720 g/L chlorothalonil) at 5 L/ha (2.5 L/acre). Make three applications at green tip, pink bud and petal fall. Do not re-enter treated areas within 48 hours of application. Do not apply within 54 days of harvest; or

Group U

Aliette WDG (80% fosetyl-Al) at 5.6 kg/ha (2.2 kg/acre) in 300 to 1000 L/ha (120 to 400 L/acre) of water. Begin sprays at the pink bud stage and continue on a 14 to 21 day interval. Do not apply more than 4 times per year. Do not apply within 1 day of harvest; or

Group 3

Quash (50% metconazole) at 180 g/ha (72 g/acre) in enough water to obtain good coverage. Apply before bloom when conditions favour disease.  Do not apply more than 3 times per year. Do not make more than 3 sequential applications. Do not apply more than 540 g/ha (216 g/acre) per season. Do not apply within 7 days of harvest; or

Group 7/11

Pristine WG (25.2 % boscalid, 12.8 % pyraclostrobin) at 1.6 kg/ha (0.64 kg/acre) in enough water to obtain good coverage. Apply before disease development. Do not apply more than 4 times per crop per season. Do not apply Pristine or other products containing Group 7 or 11 fungicides more than twice in succession. Do not enter treated fields for hand harvesting within 1 day of application. Do not enter fields for all other activities until residues have dried. If mechanical harvesting, application can be made up to the day of harvest; or

Group 11

Cabrio EG (20% pyraclostrobin) at 1.0 kg/ha (0.4 kg/acre) in enough water (up to 1000 L/ha) to get good coverage. Apply prior to disease development. Do not apply more than 4 times per season. Allow at least 10-14 days between applications. Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply within 1 day of harvest; or

Group 29

Allegro 500 (40% fluazinam) at 2.24 L/ha in 300 to 1000 L of water (0.9 L/acre in 120 to 400 L of water). Do not apply more than 4 times per season. Do not apply within 30 days of harvest.

Root and Crown Rot (Phytophthora cinnamomi and others)

Damage
Root and crown rot is primarily caused by Phytophthora cinnamomi. It can cause substantial damage to plants grown under wet conditions resulting in decline, yield loss and plant death. In addition to P. cinnamomi, several other soil pathogens, including Pythium spp, notably Pythium sterilum, can also contribute to the severity of the disease.

Symptoms

As a result of root and crown damage, leaves become yellow or reddish as they starve for nutrients. New growth may be stunted, and leaves may develop brown edges. Leaves may also start dropping from the base of the bush upwards. These symptoms are similar to those caused by nutrient deficiencies, Godronia canker or crown gall.

Affected bushes are often grouped together in low-lying or wet areas. Roots are soft and brown under the bark and the entire root system is reduced. As the infection progresses, crown tissue becomes brown under the bark.

Disease Cycle

This species of Phytophthora infects many other trees and shrubs in the Pacific Northwest and is common in soil. Infection is favoured when soils are wet over long periods as a result of compaction, poor drainage or over-irrigation. Warmer temperatures between 20-32°C favour P. cinnamomi. This is a different species from the one that causes raspberry root rot. The raspberry pathogen is favoured by cooler temperatures.

Monitoring

Examine the root system and crown of ailing plants to determine if the roots have been damaged, especially in low areas. Scrape the outer layer of tissue from the root or crown to look for the typical brown colour.

Management


Cultural control
Pre-plant.

Select suitable well-drained sites and install subsurface drainage, where needed.

Plant nursery stock at the same depth they were planted in the pots. Deep planting may cause crown death that resembles Phytophthora root rot.

Established plantings.

Carefully manage irrigation. Avoid drought stress but do not overwater and cause roots to be in wet soil for long periods.

Avoid any extra stress on the plants such as fertilizer or herbicide burn.

After heavy rains, observe areas with poor drainage. Improve the drainage in these areas.

Remove plants infected with Phytophthora.

Biological control

None.

Chemical control

Soil drench

Ridomil Gold 480SL or 480EC (480 g/L metalaxyl-M) at 37 ml per 100 m of row. Apply to the soil surface in a one-meter wide band centered over the row in spring just prior to growth. If the row spacing is 3 m (10 ft), use 0.5 L/acre. Rain or irrigation is essential to wash Ridomil into the root zone as soon as possible after application. Do not apply more than once per year. Do not apply within 80 days of harvest.

Foliar application

Aliette WDG (80% fosetyl-Al) at 5.6 kg/ha (2.2 kg/acre) in 300 to 1000 L/ha (120 to 400 L/acre) of water. Apply first spray in late spring when there is at least 7 cm of new growth and continue on a 14 to 21 day interval. Do not apply more than 4 times per year. Do not apply within 1 day of harvest; or

Confine Extra (53% mono and di-potassium salts of phosphorous acid) at 6.0 L/ha (2.4 L/acre) in enough water to provide coverage. Begin sprays when conditions are favourable for disease and continue on a 7 to 21 day interval. Do not apply more than twice in succession. Alternate with fungicides from other chemical groups. Do not apply more than 5 times per year. Do not apply within 1 day of harvest; 

Phostrol (53.6% mono- and dibasic sodium, potassium and ammonium phosphites) at 2.9 to 5.8 L/ha (1.1 to 2.3 L/acre) in a minimum of 400 L/ha of water (160 L/acre).  Begins sprays at the pink bud stage and continue on a 14 day interval.  Do not apply more than 4 times per season. Can be applied up until the day of harvest.  

Note: Phostrol may cause crop injury in the form of brown spots and marginal leaf necrosis. 

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