Pests of Specific Crops

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Pest Description Chemical Control (rate per 100 L water; or per unit area if indicated) Cultural Management Powdery Mildew (Microsphaera spp.): White, powdery growth on leaves. See General Disease Management: Powdery Mildew, Chapter 9. MAGNOLIA Diseases: Bacterial Blight (Pseudomonas syringae pv. syringae): New shoots wilt and blacken. Leaves exhibit dark, irregular spots, often with yellow haloes. Also causes twig and branch dieback. MAHONIA - OREGON GRAPE Diseases: Leaf Spot/Anthracnose (Phyllosticta spp./ Gloeosporium berberidis): The Phyllosticta fungus causes small red, circular spots that later become tan coloured in the centre. Anthracnose is characterized by larger lesions, often at the margins of leaves. Both diseases may occur together. Rust (Cumminsiella mirabilissima): Large spots on leaves become swollen and break open to release spores. This disease is very common at the Coast but is not serious except in unusually wet seasons. MALUS - APPLE and CRABAPPLE Diseases: Anthracnose Canker (Cryptosporiopsis curvispora): This destructive disease of apples in Coastal areas has also been found in the Kootenays and North Okanagan. Infection of new bark occurs in fall and causes small, red spots that lengthen and crack open the following spring forming “stringy” cankers. Large, girdling cankers kill entire branches. The fungus also causes a “bull’s eye” fruit rot. Fungicides applied for rust (see below) should also help to control leaf spot and anthracnose. DACONIL 2787F: 250 mL DACONIL Ultrex: 150 g SULPHUR (DOMESTIC): 0.4-0.9% liquid or other formulations. See label for rates and application. Cankers: Fungicides are generally ineffective in preventing spread of cankers. No products are specifically registered for control. Bull’s eye fruit rot: CAPTAN 50-WP: 6 kg/ha CAPTAN 80-WP: 3.75 kg/ha Apply if rainy periods occur before harvest. Do not apply within 7 days of harvest. Prune out and destroy infected shoots and branches in the dormant season and again if infection occurs in the spring. Space plants to provide good air drainage. See General Disease Management: Bacterial Blight and Canker, Chapter 9. Remove and destroy infected leaves. Avoid overhead irrigation. Remove and destroy infected leaves if practical. Protect new leaves. Avoid overhead irrigation in the latter part of the day. Remove and destroy severely affected trees. Prune out and burn all cankers and infected twigs in winter or whenever they are found in the year. Isolate susceptible stock from older infected apple trees to help prevent new infections. Bull’s eye rot appears in storage although fruit is infected before harvest. Fungicides are not usually needed if good pruning and cultural practices are followed. 20 • Pests of Specific Crops Nursery Production Guide
Pest Description Blister Spot (Pseudomonas syringae pv. papulans): Occurs on ‘Mutsu’ and ‘Fuji’. Light spotting on ‘Jonagold’. Spots on fruit start as small, green, water-soaked blisters, which later darken and expand to 4-5 mm in diameter. Leaves may exhibit a mid-vein necrosis and be curled and puckered; or have white to brown spots. Bacteria spread in water and overwinter in buds, leaf scars and fallen fruit. Fruit are susceptible to infection for about six weeks, starting about two weeks after petal fall. Crown Gall/Hairy Root (Agrobacterium tumefaciens / Agrobacterium rhizogenes): Large, warty or hairy growths appear on roots, crowns and stems. Galls on mature apples can be mistaken for physiological “burrknots” or wound callus. The bacteria spread in soil and drainage water and carry over in soil for many years. M9 and M26 rootstocks are susceptible to crown gall. Crown and Root Rot (Phytophthora cactorum): This soil-borne organism invades crowns of 3- to 10- year-old trees. Eventually, the trunk is girdled just below ground level and the tree dies. First indication of infection may be off-colour foliage in late summer. The problem is most serious on irrigated land in the Okanagan. European Canker (Nectria galligena): Causes severe damage to apple and pear trees at the Coast. Twigs and branches wilt and die back above cankers. First-year cankers have blistered, yellowish bark. Second-year cankers develop deeply sunken edges with concentric rings. Red fungal bodies (perithecia) may be visible at the edge of cankers in fall. Most infections occur through leaf scars during fall rains but infections can occur whenever wounding and rainfall or irrigation coincide. Fire Blight (Erwinia amylovora): M9 or M26 rootstock combined with ‘Braeburn’, ‘Fuji’ or ‘Gala’ are particularly susceptible to crown infection, although it can also occur with other rootstocks. Perennial Canker (Cryptosporiopsis perennans): Fungal cankers consist of overlapping concentric rings of woody tissue. Each year the canker enlarges, gradually girdling the limb or trunk. This disease is common in the Okanagan but rare in Coastal areas. Causes “bull’s-eye” rot on fruit. Very similar to anthracnose. Chemical Control (rate per 100 L water; or per unit area if indicated) ALIETTE WDG: 2.5 kg/ha Start at petal fall and repeat at 7 day intervals. Maximum 3 applications per year; no more than 10 kg/ha before harvest. BORDEAUX MIXTURE: 100 g COPPER 53W + 600 g HYDRATED LIME Start applying 10 days after calyx and repeat at 10 day intervals. Do not apply either product within 30 days of harvest. No effective chemical control. DYGALL (A. radiobacter) root dip is not registered for use on apples because it has been shown to be generally ineffective in preventing infection of this crop. Orchards - foliar or drench: ALIETTE WDG: Rate varies with tree density. Read label carefully. Drench: RIDOMIL GOLD: 1 mL/5 L of water/tree In Coastal areas, BORDEAUX MIXTURE as for fire blight, applied twice at leaf fall, may help reduce spread of cankers. Cultural Management The disease is worse in years when very wet weather occurs while green fruit are sizing. Follow good pruning and tree care practices; disinfect pruners between cuts. Remove fallen (windfall) fruit and bury or compost. See General Disease Management: Crown Gall, Chapter 9. Nursery stock should be planted in disease-free soil. For propagation, avoid soils and irrigation water with a history of crown rot. M4, M9 and and M26, and M2 to a lesser extent, are more resistant than other commonly-used rootstocks. The disease is worse in very wet years. Prune out infected branches below cankers and burn or bury. The fungus can continue to produce spores on dead wood. Nurseries: Destroy infected trees. Old infected apple and pear trees near the nursery should also be destroyed. See General Disease Management: Fire Blight, Chapter 9. Bull’s eye fruit rot: CAPTAN 50-WP: 6 kg/ha CAPTAN 80-WP: 3.75 kg/ha MAESTRO 80DF: 3.75 kg/ha Cankers: Research suggests fungicides are generally ineffective in preventing spread of cankers. No fungicides are specifically registered. Control the woolly apple aphid that can spread the disease. Prune out cankers whenever possible. Nursery Production Guide Pests of Specific Crops • 21
Page 1 and 2: Pests of Specific Crops 14 (updated
Page 3 and 4: Pest Description Bacterial Blight (
Page 5 and 6: Pest Description Rusts: Fungal frui
Page 7 and 8: Pest Description Mealybugs: These s
Page 9 and 10: Pest Description Insects: Mealybugs
Page 11 and 12: Pest Description CORNUS - DOGWOOD D
Page 13 and 14: Pest Description Insects: Cotoneast
Page 15 and 16: Pest Description Leaf Spot (Cercosp
Page 17 and 18: Pest Description Web Blight (Rhizoc
Page 19: Pest Description Juniper Webworm (D
Page 23 and 24: Pest Description Insects and Mites:
Page 25 and 26: Pest Description Sydowia Blight/Tip
Page 27 and 28: Pest Description Needle Cast (Cycla
Page 29 and 30: Pest Description Sooty Mould: Black
Page 31 and 32: Pest Description Coryneum Blight, S
Page 33 and 34: Pest Description PSEUDOTSUGA - DOUG
Page 35 and 36: Pest Description Pear Trellis Rust
Page 37 and 38: Pest Description ROBINIA Diseases:
Page 39 and 40: Pest Description SALIX - WILLOW Dis
Page 41 and 42: Pest Description Berckmann’s Blig
Page 43 and 44: Pest Description ULMUS - ELM Diseas

Pests of Specific Crops

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