Raspbery Spur blight
|
Raspberry Spur Blight
 Raspberry Spur Blight is a fungal disease caused by Didymella applanata. This disease thrives in wet conditions and is spread by rain and wind, especially during a damp spring.Susceptible Plants- Raspberry and loganberry Symptoms- Raspberry Spur Blight symptoms first appear on young first-year canes in late spring or early summer. Purple to brown areas (lesions) appear just below the leaf or bud, usually on the lower portion of the stem. These lesions expand, sometimes covering all the area between two leaves. In late summer or early fall, bark in the affected area splits lengthwise and small black specks, which are fungal fruiting bodies appear in the lesions. They are followed shortly by many slightly larger, black, erupting spots; another form of fungal fruiting body. Leaflets sometimes become infected and show brown, wedge-shaped diseased areas, with the widest portion of the wedge toward the tip of the leaf. Infected leaflets may fall off, leaving only petioles without leaf blades attached to the cane. When diseased canes become fruiting floricanes during the next season, the side branches growing from diseased buds are often weak and withered. The raspberry spur blight fungus has been reported to reduce yields in several ways. It can blight the fruit bearing spurs that are produced on the side branches, cause premature leaf drop, and kill buds on the canes that later develop into fruit bearing side branches. In addition, berries produced on diseased canes may be dry, small and seedy.
Prevention and Control- Cut and burn diseased canes. In spring, thin canes to reduce overcrowding. Cultivars ‘Boyne’ and ‘Festival’ have some resistance to raspberry spur blight.
Excessive applications of fertilizer (especially nitrogen) should be avoided, since it promotes excessive growth of very susceptible succulent plant tissue. Plants should be maintained in narrow rows and thinned to improve air circulation and allow better light penetration. Weeds are very effective in reducing air movement; therefore, good weed control within and between rows is important for improving air circulation within the planting. Fungicide Spray- Where the raspberry spur blight disease has been a problem, spray with Bonide Copper Fungicide Bordeaux Spray
|
|
