My question concerns my plum tree which is about 14 years old. It produces a combination of a prune plum and a yellow plum, I believe it was grafted in its infancy! It has these big brown gnarly "growths" on most of the branches and now (first time this has happened) it has tiny little white spiders all over the leaves. I am thinking because it is quite big I will never be able to spray it enough to get rid of the bugs, that I should just prune it right back to the main branches (there would be no foliage left)? These little white things are spreading to my flower garden quickly.
Hello, It sounds like your plum tree has black knot. If the black knot occurs infrequently on the small limbs they can be pruned out and burned. Prune to 5 to 10 cm below the growth. Do not prune to the major limbs as you described in your post. This will either kill your tree or cause water sprouts, weakly attached growth arising from the tree. If you are considering this more extreme measure you should simply cut the tree down (and I am not suggesting that you do). It is possible that the small insects that you see are spider mite. Here is link with a photograph, and a second to show the variation in the appearance of the two-spotted spider mite. The two spotted spider mite damage appears as leaf stippling and webbing on the leaves. Plum rust mites cause the leaves to take on a silver hue and curl up. Be sure of the identification of the insect before you attempt to control the problem. If you do find that you have spider mites there are a couple things to consider. Spider mites dislike rain, humidity and cool weather. It is raining at UBC today, I wonder if it is raining in Delta? If so the population may be reduced. Additionally there are a number of naturally occurring predatory insects that will help to keep the population in check. They will be attracted to your tree as spider mite numbers increase. There has to be a threshold level before you take things into your own hands. Here is a link link for organic control methods if you are looking for more suggestions. Raakel
