By Moorton
United Kingdom 
My pyracantha has developed a cankerous growth with produces a white sticky cottonlike appearance . it effects 20% of the plant but the remaining still produces some white flowers and berries.any advice on treatment would be most helpful Thanks
31 Jul, 2010
Answers
it could also be scale insect, but as Tugbrethil says, provado will eliminate them.
31 Jul, 2010
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Welcome, Moorton!
By cankerous growth, do you mean distorted stems and foliage on some branches, or tumor- like growths on the thicker branches? You might have more than one problem going.
When I hear "white sticky cotton" in conjunction with Pyracantha my first thought is wooly aphid. If it's them, somewhere under that wool is a pear-shaped, gray, white, or pinkish, pinhead-sized bug. They aren't all that easy to get rid of, but Provado will eventually do it, with consistent, thorough spraying, and/or with a soil drench.
31 Jul, 2010