WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Cane Blight

(Leptosphaeria coniothyrium)

Insects and Invertebrates

 

Cane Blight

 

Symptoms

Cane blight is not commonly found in the Pacific Northwest, but if present can be quite serious; it can weaken fruiting canes, wilt plants, and reduce yield. The fungus invades through wounds, such as those resulting from fruit catching plates of mechanical harvesters, pruning, and insect damage. Dark brown to purplish cankers form on new canes near the end of the season where wounds are present. The cankers enlarge and extend down the cane or encircle it, causing lateral shoots above the diseased area to wilt and eventually die. Black reproductive fungus bodies (pycnidia) develop within the brown cankered bark. In wet weather, large numbers of microscopic spores ooze from the pycnidia which give the bark a dark-gray, smudgy appearance. During winter, infected canes commonly become cracked, brittle, and snap off easily. Wilting death may also occur on the side branches of infected floricanes typically between blossoming and fruit ripening. Early cane blight infections may resemble spur blight; however, cane blight usually covers the whole stem and is not confined to the leaf node areas as with spur blight.

 

Cane Blight

 

Life History

The cane blight pathogen survives over winter on infected or dead canes. The following spring, spores are released during wet periods. These spores are carried by splashing rain or overhead irrigation, wind, and insects to nearby canes. Under moist conditions, spores germinate and penetrate any type of wound, rapidly killing cane tissue. Fungal fruiting bodies are formed in older cankers which complete the disease cycle. Infection occurs at almost any time during the growing season. Dead canes continue to produce reproductive spores and remain a source of infection for several years. Young canes are most susceptible to infection.

 

Monitoring

Scout 3-5 sites per field, (depending on field size) and evaluate 10-20 hills, spaced 3-5 hills apart on both sides of the aisle way. In early spring, infected tissue appears as a reddish lesion up the cane from the wound site. Examine floricanes at the catcher plate height by scraping the bark away to inspect the vascular tissue. External symptoms are usually not visible on primocanes during harvest. Suspect areas should be checked closely in the fall by scraping away the epidermis of primocanes near wounds. In infected canes, a vertical, reddish or brown stripe lesion within the vascular tissue can be seen. Record percent infected hills.

 

Cane Blight

 

Thresholds and Management

The best timing for fungicide applications is during or immediately after harvest, but inspection during the dormant and pre-bloom period confirms presence of the disease. Treatment should be considered in fields with a history of the disease or where monitoring has revealed that 1-3% of primocanes and/or floricanes are infected. Make sure that the bottom half of canes receive adequate fungicide coverage. Cane blight infection is likely to be more severe in years where heavy rainfall occurred during the harvest period.

The incidence of disease can be minimized by adopting and following proper management techniques. Adjust the fruit catcher plates on the mechanical harvester to minimize wounding. Improve air circulation within the canopy by keeping fruiting rows narrow, spacing canes adequately, and controlling weeds. Adjust irrigation to reduce the number and duration of wet periods. Avoid excessive use of nitrogen fertilizers, since it promotes excessive growth of very susceptible succulent plant tissue. After harvest, remove and destroy floricanes and any new primocanes that are infected before growth starts in the spring.

 

Resources

Cornel University, Department of Horticulture: Managing Raspberry Cane Diseases
http://www.fruit.cornell.edu/berry/ipm/ipmpdfs/Raspberry%20cane%20disease%20mgmt.pdf

Ohio State University Extension: Cane Blight of Raspberries
http://ohioline.osu.edu/hyg-fact/3000/pdf/HYG_3202_08.pdf

Oregon State University Extension, An Online Guide to Plant Disease Control: Raspberry – Cane Blight
http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=945

University of Illinois Extension, Integrated Pest Management: Spur Blight and Cane Blight of Raspberries
http://ipm.illinois.edu/fruits/diseases/spur_blight/index.html

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WSU Whatcom County Extension 1000 N. Forest St., Suite 201, Bellingham, WA 98225 (360) 778-5800 whatcom@wsu.edu