Diseases
Black Root Rot
Damage
Black root rot mainly affects bearing plants but may occur on the main roots of young runner plants. It causes poor yields and serious plant losses.
Symptoms
Roots. The outer layers of main roots are usually black while the core remains a normal whitish colour. The root system fails to produce new roots. If new roots occur, they have black areas. The roots of seriously affected plants will be completely black, including the core, and eventually rot away.
Leaves. The foliage is a poor colour and reduced in size. Seriously affected plants may wilt and die when berries are ripening.
Disease Cycle
This condition is caused by a combination of factors including Rhizoctonia, Pythium, other root rot fungi, pathogenic nematodes, water-logged or compacted soil, and cold injury.
Monitoring
Look for the black discolouration on the outside of the main roots. Carefully scrape the outer layer of the root away to check the colour of its core. Except with dying plants, the core should be a creamy-white colour. Any new roots that are present will have black areas. Do not confuse black root rot with the natural darkening of older roots of healthy plants. These plants will produce new, creamy-coloured, healthy roots without the blackened areas.
Management
Cultural control
Plant only certified stock on well-drained fertile soils.
Use a long rotation (at least 2-3 years) between strawberry crops.
Improve the winter drainage by subsoiling between the rows, or planting on raised beds.
Chemical control
Soil fumigation before planting may reduce the problem.
In fields with a history of black root rot, apply:
Quadris (250 g/L azoxystrobin) at 6 mL/100 m of row as an in-furrow application at planting or at 1.1 L/ha (0.44 L/acre) as a banded drench within 8 days of planting. Post-plant drench should be in a 20 cm band over the row. Do not apply to day-neutral (ever-bearing) strawberries. A plant back interval of 30 days for broadleaf and root crops, and of 45 days for cereals is required. Do not apply within 365 days of harvest; or
Scholar 230 SC (230 g/L fludioxonil) at 1.2 L/ha (0.48 L/acre) or 6.5 mL/100 m of row as a drench application in a 15 to 20 cm band over the row. Use sufficient water to ensure even and thorough coverage. For new plantings apply within one week of transplanting and repeat in late July/early August. For established plantings apply in the spring when leaves emerge and repeat after renovation. Do not apply more than two times per year over two years. Do not apply more than 552 g/ha (220 g/acre) per season. Do not apply within 1 day of harvest.
Scholar may also be applied through a drip irrigation system. Refer to the product label for more information.
Fruit Rots
Several different fungal organisms cause fruit rot. The main cause is Botrytis (grey mould). Rhizopus (leak) usually occurs after harvest but may develop on ripe fruit in the field in warm weather. Fruit infected with Rhizopus softens rapidly and collapses. Anthracnose infected fruit can be a problem in summer-harvested dayneutral varieties. Botrytis fruit rot is described below. A fungicide program for Botrytis will also control other fruit rot organisms such as Rhizopus and Cladosporium.
Anthracnose (Colletotrichum spp.)
Damage
Anthracnose can affect leaves, petioles, runners, crowns, buds, blossoms and fruits. It is caused by several species of the fungus Colletotrichum; C. fragariae, C. gloeosporioides and C. acutatum. Although, anthracnose has generally been considered to be a “warm weather” or “southern” disease of strawberry, over the past few years, incidence of fruit anthracnose, associated with C. acutatum, has been reported from the northern US and BC. Fully opened flowers and ripening fruit are most susceptible to infection. In BC, this disease has not been severe to date, causing only limited fruit rot in late harvested June-bearing varieties and on day neutral varieties harvested through the summer. However, anthracnose should be monitored carefully to determine if incidence is increasing so appropriate preventative action can be taken.
Symptoms
On petioles and runners, symptoms first appear as dark spots, and then develop into elongated, dry, sunken lesions which girdle the plant tissue resulting in wilting and death of leaves or entire daughter plants. On leaves, anthracnose appears as small black spots and, in some cases, dark-brown to black lesions appear on leaf margins and tips. The fungus sporulates on these lesions and becomes an inoculum source for flower, fruit, and crown infections. Infected flowers become blighted and dry quickly. On fruit, symptoms appear as whitish, water soaked lesions, and later turn into dark-brown to black, sunken lesions with pale-orange to salmon-colored spore masses. When crown tissue becomes infected, crown rot may develop and the entire plant may wilt and die. The internal crown tissue will show reddish-brown to dark-brown discoloration.
Disease Cycle
Infected transplants and soil associated with transplants appear to be the primary source of inoculum. Once the disease is established in the field, the fungus can overwinter on infected plants and plant debris, such as dead leaves and mummified fruits. In spring and early summer, spores are produced in abundance on previously infected plant materials. Spores are spread by splashing or wind-driven rain or irrigation, by people or equipment moving through the field. Spore germination, infection and spore production of the fungus are favoured by warm, humid weather and rainfall.
Monitoring
Watch the crop during the early growing season for foliar symptoms that may lead to heavy infections later in the season, especially on ripening fruit.
Management
Cultural control
Use disease-free planting stock.
The fungus is spread by splashing water. If using overhead irrigation, sprinkle in the early morning so plants dry during the day, thus minimizing new infections.
Remove old, infected plant debris including infected berries during harvest.
Narrow rows to leave enough space for air movement to encourage rapid drying.
Spores can spread on containers and flats; therefore avoid moving such items from farm to farm. Practice good disinfection and sanitation measures.
Cool fruit as soon as possible after harvest to minimize post-harvest rot.
Chemical control
In fields with a history of anthracnose, apply one of the following fungicides beginning at early bloom:
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 5 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 apply within 1 day of harvest; or
Group 11
Cabrio EG (20% pyraclostrobin) 0.56 to 1.0 kg/ha (225 to 450 g/acre) in at least 1000 L/ha (400 L/acre). Begin applications no later than bloom and repeat applications as required at 7 to 14 day intervals. Do not apply more than 5 times per season. Do not apply within 1 day of harvest.
Note:Cabrio and Pristine applied for anthracnose control will also provide suppression of powdery mildew.
Botrytis Fruit Rot (Grey Mould) (Botrytis cinerea)
Damage
Botrytis can cause very serious crop losses, especially in wet seasons. The disease affects all stages of fruit development from blossoming through post-harvest marketing. Rot can occur on blossoms, blossom stems, and green and ripe berries. After harvest, the disease can spread rapidly from rotted to healthy berries, causing whole loads to be unmarketable. If not controlled by a spray program, losses of fruit can be expected every year.
Symptoms
Blossoms. Affected flowers turn brown and may be killed. Infection of the flower stem causes it to collapse. A fuzzy, grey growth sometimes develops on the brown petals and stems.
Berries. The infection starts as a light-brown spot, usually near the stem, which spreads over the entire berry. Rotted berries have the characteristic fuzzy, grey growth of the fungus. This growth contains spores which spread easily to other berries and blossoms.
Disease Cycle
Botrytis over-winters in old leaves and fall fruit. In the spring, the fungus produces spores which infect the blossoms. The fungus grows down through the flower parts into the young green berries as they develop. Infected green fruit may not show symptoms until they ripen. The grey mould produces abundant spores which cause more infections.
Monitoring
Cool, wet weather and high humidity favour the disease. Start applying protectant sprays when the first flowers open. Bravo 500 or Echo 720 should be applied earlier (see below).
Management
Cultural control
Renovate and rotovate in early spring to remove and destroy old leaves and fruit.
Fertilize for optimum leaf growth.
Over-fertilization with nitrogen before harvest can cause excessive growth and increase fruit rot.
Manage row spacing and row widths to allow adequate air movement and rapid drying of leaves.
Time irrigation so flowers and leaves dry off quickly.
Control weeds to reduce humidity around the plants and carry-over of disease.
Ensure that fields are picked clean and discard any rotten berries away from the field.
Keep harvested berries in the shade until they are removed from the field. Covering flats with a reflective tarp will help reduce heating.
Cool fruit destined for the fresh market (best to 1°C) as soon as possible after harvest to slow down disease development.
Chemical control
Refer to Fungicide Chart in this section.
Fungicide sprays must be applied regularly to prevent the disease from becoming established in the blossoms and developing fruit. Apply the first spray when the first blossoms open, and repeat every 7-14 days depending on weather. Observe days to harvest and re-entry times listed on product labels.
To obtain adequate coverage, use at least 1000 L/ha (400 L/acre) of water. To delay development of resistance, rotate sprays from the different groups listed below. Never apply fungicides from the same group more than twice in succession.
| Strawberry Botrytis Fruit Rot (Gray Mould) Fungicides | ||||
| PRODUCT | ACTIVE | RATE | PHI* | COMMENTS |
| Group 2 Fungicides | ||||
|
Rovral WP or Rovral WDG |
500 g/L iprodione | 2 kg/ha (0.8kg/acre) | 1 |
|
| Group 7 Fungicides | ||||
| Cantus WDG | 70% boscalid |
560 g/ha (224 g/acre) |
0 |
|
| Fontellis | 200 g/L penthiopyrad | 1.0 to 1.75 L/ha ( 0.4 to 0.7 L/acre) | 0 |
|
| Kenja 400SC | 400 g/L isofetamid | 1.0 to 1.24 L/ha (0.4 to 0.5 L/acre) | 0 |
|
| Sercadis | ||||
| Group 7/Group 9 Fungicides | ||||
| Luna Tranquility | 125 g/L fluopyram 375 g/L pyrimethanil | 1200 ml/ha (486 ml/acre) | 1 |
|
| Group 7 / Group 11 Fungicides | ||||
| Pristine WG | 25.2% boscalid 12.8% pyraclostrobin | 1.3 to 1.6 kg/ha (0.52 to 0.64 kg/acre) | 1 |
|
| Group 17 Fungicides | ||||
| Elevate 50 WDG | 50% fenhexamid | 1.7 kg/ha (0.7 kg/acre) | 1 |
|
|
Elevate 50 WDG |
50% fenhexamid 80% captan |
1.2 to 1.7 kg/ha (0.5 to 0.7 kg/acre) 2.75 kg/ha (1.1 kg/acre) |
2 |
|
| Group 9 Fungicides | ||||
| Scala SC | (400 g/L pyrimethanil) | 2.0 L/ha (0.8 L/acre) | 1 |
|
| Group 9/12 Group Fungicides | ||||
| Switch 62.5 | (37.5% cyprodinil and 25% fludioxinil) | 975 g/ha (390 g/acre) | 1 |
|
| Group M Fungicides | ||||
|
Captan 80 WDG |
80% captan 50% captan 80% captan |
2.8 to 4.2 kg/ha (1.1 to 1.7 kg/acre) 4.5 to 6.75 kg/ha (1.8 to 2.7 kg/acre) 2.75 to 4.25 kg/ha (1.1 to 1.7 kg/acre) |
2 |
|
| Folpan 50 WP | 50% folpet | 2.0 kg in 1000 L water | 1 | |
| Thiram 75 W | 75% thiram | 2.25 to 2.5 kg in 1000 L of water | 3 | |
|
Bravo 500 Echo 720 |
500 g/L chlorothalonil 720 g/L chlorothalonil |
3.5 L/ha (1.4 L/acre) 2.4 L/ha (1.0 L/acre) |
30 |
|
| Biological Fungicides | ||||
| Serenade Opti |
Bacillus subtilis |
1.7 to 3.3 kg/ha (0.68 to 1.32 kg/acre) | 0 |
|
| Regalia Maxx | 20 % Reynoutria sachalinensis | 0.125 to 0.25 % v/v in 500 to 1,000 L/ha water (200 to 400 L/acre). | 0 |
|
| Actinovate SP | 0.037% Streptomyces lydicus | 425 g/1100 L water | 0 |
|
| Double Nickel 55 | Bacillus amyloliquefaciens | 0.6-2.5 kg/ha (0.23-1 kg/acre) | 0 |
|
| Timorex Gold | 23.8% tea tree oil | 1.5-2.0 L/ha (0.6 -0,8 L/acre) in 400-800 L/ha (160-320 L/ac) | 2 |
|
*PHI - Pre Harvest Interval
Note: Serenade Max no longer produced.
Common Leaf Spot (Ramularia Spot or Bird’s-eye Spot) (Mycosphaerella fragariae)
Damage
When the spots are numerous, common leaf spot can reduce plant vigour, yield and fruit quality. Minor infections do not cause significant damage.
Symptoms
The disease first appears as small, red or purplish spots. As the spots get larger, they turn grey or light brown in the centre with purplish edges. The disease is most often seen on leaves and petioles but similar symptoms may occur on runners, flower stems, and fruit. Flower stem infection can cause blossom drop on very susceptible varieties. Fruit infection results in “black seed” disease –hard, brown spots on the fruit.
Disease Cycle
The common leaf spot fungus can survive on infected transplants in cold storage, and on plant debris in the soil. The disease develops and spreads during wet weather when temperatures are from 7 to 25°C. It is most severe in the spring and fall. The spores are moved by splashing rain or irrigation. Infection occurs on leaves or stems that are wet for at least 12 hours.
Monitoring
Start to watch for leaf spots when the first new leaves are fully open in the spring. The disease can spread rapidly during periods of prolonged wet weather and may reach damaging levels on susceptible varieties.
Management
Cultural control
Most varieties show some resistance but may develop the disease during long wet periods. Puget Reliance and Shuksan are very susceptible.
Use certified disease-free planting stock.
Mow and rotovate old leaf debris in the spring and renovate after harvest, to reduce disease.
Chemical control
If leaf spotting is severe in the spring a fungicide application may be necessary. Puget Reliance and other susceptible varieties should be sprayed 7-14 days before blossoms start to open. Fall infections generally do not need to be controlled with fungicides.
Apply:
Topas 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) in enough water to obtain good coverage when leaf spots are detected in the spring. Do not apply more than two consecutive applications of Topas. Do not apply more than 4 times per season. Do not apply within 1 day of harvest; or
Captan 80 WDG (80% captan) at 2.8 to 4.2 kg/ha (1.1 to 1.7 kg/acre). Do not re-enter treated fields within 48 hours of application. Do not apply within 2 days of harvest; or
Captan 50 WP (50% captan) at 4.5 to 6.75 kg/ha (1.8 to 2.7 kg/acre). Do not re-enter treated fields withing 48 hours of application. Do not apply within 2 days of harvest; or
Senator 70 WP (70% thiophanate-methyl) at 1.1 kg/ha (440 g/acre) commencing when buds are visible in the crown. Repeat every 7-10 days as needed and reduce spray interval to 3-5 days during rainy periods. Do not apply within 1 day of harvest; or
Folpan 50 WP (50% Folpet) at 2 kg/ha (0.8 kg/acre) in 1000 to 2000 L of water/ha (400 to 800 L/acre). Apply before first infection and repeat at 7 day intervals to protect crop until harvest. Do not apply within 1 day of harvest.
Other products recommended for Botrytis fruit rot control will also suppress leaf spot.
Occasionally, other fungi, such as Phomopsis, may cause leaf spots but these are usually controlled by sprays used for fruit rot.
Nematodes
For detailed information on this pest refer to “General Berry Pests – Nematodes”.
Damage
Nematodes are microscopic worms that live in the soil. When plant parasitic nematodes are present in large numbers, they cause stunting and reduced vigour of plants by feeding on the roots. Damage is usually patchy in fields.
Management
New fields should be sampled for nematodes in the year before planting so fumigation can be done in late summer or early fall, if necessary. Compost or manure should always be applied the following spring after fumigation treatment.
See “General Berry Pests—Nematodes” in this guide for details on soil sampling, field preparation and application of fumigants.
Powdery Mildew (Podosphaera aphanis (syn Sphaerotheca macularis)
Damage
This fungal disease attacks flowers, leaves and fruit and can cause heavy crop losses during warm, humid conditions. There are no completely resistant varieties, but Hood and Totem have shown some tolerance. Shuksan is moderately susceptible. Damage can be severe on dayneutral varieties.
Symptoms
Leaves. Infected leaves curl upward exposing the white powdery fungus on the underside. Diseased leaves later turn reddish purple or have small purple flecks or spots.
Flowers. Flowers are covered with white mycelium and may be deformed or killed. Poor pollination leads to poor fruit set.
Fruit. Infections on green fruit can stop ripening, leaving hard, russetted and cracked fruit. On ripening fruit, the fungus first grows under individual seeds, raising them from the fruit surface. The white, powdery fungus then spreads over the surface of the fruit. Infected ripe berries may be firm, or soft and pulpy, and usually have a somewhat flat, or bitter taste.
Disease Cycle
The disease overwinters in infected leaves. Spores produced on infected plants or debris, are carried by wind to infect new spring growth. The disease develops in moderate to high humidity and warm temperatures (15 to 27°C).
Monitoring
Watch for the first signs of the disease—leaf distortion (curling) and a general purple discolouration—especially in the spring and fall. Closely monitor dayneutral varieties for mildew on the leaves and fruit during the late summer and early fall when days are warm with heavy evening dews.
Management
Cultural control
Renovate plantings soon after harvest to destroy old, infected foliage.
Chemical control
Apply fungicides when the disease is first seen, especially during warm, humid conditions. If the disease was a problem the previous year, apply sprays before symptoms appear. It is usually not necessary to spray after harvest in August or September except for very susceptible and dayneutral varieties.
Use:
Lime Sulphur at 15 L/ha applied in 1000 L/ha of water (6.0 L/acre in 400 L/acre water). Apply when foliage is dry. Apply well before fruit ripening or after harvest.
Cueva (Copper octoanate 1.8%) Use a 0.5% to 2% solution,applied at 470-940 L/ha (188-377 L/acre). Apply 1 month after planting or before flowering on established plants, and twice more at 7 day intervals. Do not apply within 1 day of harvest, or
Group 3
Nova 40W (40% myclobutanil) at 340 g/ha (145 g/acre) in enough water to ensure thorough spray coverage (500 to 1000 L/ha). Begin applications when disease first appears or when conditions favour disease development. Repeat applications as required at 14 to 21 day intervals. Do not apply more than two consecutive applications of Nova or other Group 3 fungicides. Do not apply more than 6 times per season. Do not apply within 3 days of harvest; or
Mettle 125 ME (125 g/L tetraconazole) at 219 to 365 mL/ha (88 to 146 mL/acre) in enough water to ensure thorough spray coverage. Begin applications when disease first appears or when conditions favour disease development. Repeat applications as required at 14 to 21 day intervals. Do not apply more than two consecutive applications of Mettle or other Group 3 fungicides. Do not apply more than 4 times per season. May be used up until the day of harvest; or
Fullback 125SC (125 g/L flutriafol) at 510 to 1024 mL/ha (200 to 400 mL/acre) in enough water to ensure thorough spray coverage. A nonionic surfactant at 0.25 v/v may be added to the spray mix. Do not apply more that 2048 mL/ha (800 mL/acre) per season. Do not apply within 8 days of harvest.
Group 7
Luna Privilege (500 g/L fluopyram) at 500 mL/ha (200 mL/acre) applied through the drip irrigation system preventatively. Apply as needed on a 5 to 7 day interval. Do not exceed 1.0 L/ha (400 mL/acre) per season. Do not apply Luna Privilege or other products containing Group 7 fungicides more than twice in succession. May be used up until the day of harvest; or
Sercadis (300 g/L fluxapyroxad) at 250-333 mL/ha (100-135 mL/acre) in enough water to obtain good coverage. Apply beginning no later than 10% 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
Velum Prime (500 g/L fluopyram) at 500 mL/ha (200 mL/acre) through the drip irrigation system only. Apply preventatively and continue on a 5 to 7 day interval as needed. Do not apply more than two sequential applications of any group 7 fungicide before rotating with a fungicide from another group. Do not apply more than 500g of fluopyram/ha per year. Can be applied up until the day of harvest; or
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 preventatively and repeat as required at 7 to 14 day intervals. Do not apply within 1 day 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 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 5 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 apply within 1 day of harvest; or
Group 11
Flint (50 % trifloxystrobin) at 140 g/ha (56 g/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 3 times per crop per season. Do not apply Flint or other products containing Group 11 fungicides more than twice in succession. May be applied up to the day of harvest; or
Group 13
Quintec (250 g/L quinoxyfen) at 300 to 440 mL/ha (120 to 176 mL/acre) as a preventive treatment before visible powdery mildew symptoms appear. Use enough water to ensure thorough coverage of foliage. Use the high rate when disease pressure is severe. Repeat as required at 10 to 14 day intervals. Do not make more than 2 consecutive applications of Quintec. Alternate with fungicides from other groups to delay development of resistance. Do not apply more than 4 times per season. Do not apply within 1 day of harvest.
Biological Fungicides
Actinovate SP (0.037% Streptomyces lydicus) at 425 g/1100 L of water. Apply as a foliar spray ensuring coverage of leaves and blossoms. Make the first application when conditions are conducive to disease development and repeat applications every 7 to 14 days. Use the shorter application interval under high disease pressure. Approved for organic production. May be used up until the day of harvest; or
Regalia Maxx (20 % Reynoutria sachalinensis) at 0.125 to 0.25 % v/v in 500 to 1,000 L/ha water (200 to 400 L/acre). Apply as a preventive foliar spray when disease symptoms first appear ensuring coverage of leaves and blossoms. Repeat applications every 7 to 10 days depending on disease pressure. May be used up until the day of harvest; or
Double Nickel 55 (Bacillus amyloliquefaciens strain D747 at 5X1010 spores/g) at 0.5 to 2.5 kg/ha (0.20 to 1 kg/acre) as a foliar spray in enough water to ensure coverage. Apply at or just before flowering until fruit maturity if conditions favour disease development. Use the low rate (0.2 to 0.4 kg/acre) when plants are small or disease pressure is low, and the high rate (0.4 to 1 kg/acre) when disease pressure is high. Repeat applications every 3 to 10 days depending on disease pressure. May be used up until the day of harvest; or
Timorex Gold (Tea tree oil 23.8%) at 2-8 L/ha (0.8-3.2 L/acre) in 400 to 800 L/ha (160-320 L/acre). Apply at 7-14 days intervals for preventive treatments depending on disease level. Do not apply within 2 days of harvest.
Note: Avoid spraying in the heat of the day or when temperatures are above 35 C. Do not spray this product through irrigation system.
Red Stele Root Rot (Phytophthora fragariae)
Damage
This is a common disease, especially in the Fraser Valley. It can cause serious plant losses and poor yields.
Identification
Roots
In early spring, the central core (or stele) of infected roots is a pinkish-red colour, turning to black-red. Feeder roots may rot away completely, giving the main root a “rat-tail” look.
Left – Healthy Strawberry Root
Centre – Early stage red stele root rot
Right – Advanced stage of red stele root rot
Far Right – Black root rot
Leaves
The leaves turn a red, yellow or pale green colour early in the season from lack of nutrient uptake. Severely infected plants are undernourished and stunted. The plants eventually wilt and die.
Disease Cycle
The disease is caused by a fungus-like organism called Phytophthora fragariae var. fragariae. It lives in the soil and attacks the roots. It attacks only strawberries, but can remain in the soil for many years without strawberries being present.
Infection occurs in cool, wet soil at temperatures from 1 to 10o C. The most damaging periods for infection are during the formation of new adventitious roots in the fall and new feeder roots in early spring. The disease is much more severe under conditions of poor drainage and will often appear in low spots in the field.
In water-logged soils, Pythium and other Phytophthora species may also cause root and crown rots (see Black Root Rot).
Monitoring
In early spring, carefully scrape the infected tips of the main roots, or slip off the outside layer of the root, to see the pinkish-red to black-red colour of the stele. This symptom usually disappears when soil temperatures rise in June.
Management
Cultural control
Use certified disease-free planting stock. This prevents soil contamination and is the best method of controlling red stele.
Plant only on well-drained sites.
Do not grow strawberries repeatedly in the same field.
Avoid fields where the disease has been severe in the past.
If the disease is present, improve the winter drainage and subsoil between the rows.
Choose varieties showing some resistance to red stele (Puget Reliance and Rainier). These may become infected if certain races of the fungus are present.
Chemical control
If necessary, apply:
Ridomil Gold 480SL or 480EC(480 g/L metalaxyl-M) at 20 ml per 200 meters of row in a 0.5 m wide band (30 ml per 1000 ft. row per 20 inch band) centered over the row. At a 110 cm (44in) row spacing, this works out to 0.9 L/ha (0.4 L/acre).
Apply in late October or November when the soils are cool and damp. Ridomil moves readily into the soil root zone with rain. Do not apply after November 30.
Aliette WDG or Aliette WP (89% fosetyl-Al) at 5.6 kg/ha (2.2 kg/acre. Apply as a directed spray to young growing leaves in spring and/or in fall before leaves die. This fungicide is taken up by the leaves and moves down into the plant roots. Apply not more than 4 times/year (twice in spring and twice in the fall), with applications 30 to 60 days apart. Where Ridomil resistance is not a problem, Ridomil may be applied in the fall and Aliette in the spring. Do not apply within 30 days of harvest.
Verticillium Wilt (Verticillium dahliae)
Damage
This disease is not common in the Fraser Valley but can appear in strawberry plantings that follow potatoes or raspberries. It is more common in the southern Interior.
Symptoms
Young, infected leaves in the centre of the plant are small, bluish and dull. Older leaves curl up along the mid-vein, turn brown along the edges and between veins. They may also turn a yellow or reddish colour and wilt. The leaves dry up as the disease progresses. Browning of the older leaves while the younger leaves remain green is typical of Verticillium wilt. Individual plants or small patches of plants in the field may wilt and die during the summer following planting. The plants are often stunted. Brownish streaks occur in the vascular tissue of crown, roots or base of the leaf stem.
Disease Cycle
The disease is caused by a soil-borne fungus called Verticillium. It enters the roots and moves up through the vascular system of the plant. It inhibits the movement of water and nutrients to the leaves. The disease is more severe on light, sandy soils where root lesion nematodes are also present.
Monitoring
To check plants suspected of Verticillium wilt, slice open the crown to look for the brownish streaks often seen in the vascular tissue. This disease can be mistaken for other crown or root rots. A laboratory diagnosis may be necessary to confirm this disease.
Management
Cultural control
Avoid planting susceptible varieties (especially Shuksan) where the disease is likely to cause losses.
Avoid planting strawberries in fields planted to potatoes, raspberries or alfalfa the previous year.
Chemical control
Soil fumigation reduces the disease temporarily but will not eliminate it.
