Raspberries - spur blight
Many people will not grow raspberries because they are so many reasons for the plants to fail. In this area, the worst problem seems to be spur blight. This is a fungus which attacks leaf buds from the beginning of the growing season until the fruits form - assuming the plants last that long. The first I knew about it was when my leaf buds turned brown either before or during opening.
The fungus isn't difficult to spot, once you know the signs. Look at the stems; the skin will appear dry and cracked, and there will be dark purple or brown stains beginning at ground level and going up the stem. Closer inspection will reveal the fruiting bodies of the fungus. The dry, cracked skin on the stems, however, is unmistakeable.
If untreated, you might get some fruit, but it will be a race between the speed at which the fruit forms and ripens and the rate of ascent of blight up the stem.
Fungus thrives in damp conditions where there's too much foliage and not enough air movement. Anything you can do to get air through the plants and hinder the fungus will help.
I've found the following procedures all help:
*Spray the base of the stems with Bordeaux mixture (up to a height of about a foot) regularly through the winter - say 3 or 4 times altogether.
*Cut out all dead wood when it's fruited. This removes overwintering fungus.
*When the new canes grow, strip off lower leaves to a height of about a foot, and dispose of them. This helps get air through the plants.
*Continue to spray the base of the stems - old and new - through the spring and summer.
These measures should ensure that you get a decent crop.
One other point worth noting is that yellow canes are not so prone to spur blight, and nor are autumn fruiting varieties. Perhaps this is because there are fewer overwintering canes.
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