For Release April 18, 2004
Trees That Need Attention
by Chuck Otte, Geary County Extension Agent
There are two subjects in today's column. The only thing that they have in common is that they are both dealing with woody plants. One is pine trees, especially Mugo and Scot's pines and the other is flowering crabapples.
If you have short needled pines such as Mugo or Scot's pines, you need to be looking for the European Pine Sawfly larvae. This pest does not feed on spruce trees or on junper/cedar trees and only rarely on long needled pines like Austrian pines. The dark greenish black larvae (worms) will be hatching any day now.
They will usually be found on the branch tips. At first look for curly white needles that have had the green eaten off of them by the very small larvae. Later on they will devour entire needles. They tend to stay all bunched together and if they are disturbed, they will move in a rather jerky fashion in unison. Fortunately they are easily found (if you are looking for them), there is only one generation per year, they are readily controlled with many tree insecticides and they are gone before the new growth emerges so damage is quickly covered up.
Don't spray for them unless you find them. Use a hose end sprayer to insure good thorough coverage of the tree or bush. Use a labeled insecticide such as carbaryl, permethrin, cyfluthrin or acephate following label directions for mixing.
The flowering crabapple trees have been spectacular! But many homeowners do not like the little fruit that comes on after the flowers go away. On the one hand, they are a nuisance. Sometimes they fall off all over the sidewalk. They are certainly too small to eat, or at least for us to eat. And if the birds eat them, they often leave other little deposits behind! But if you happen to enjoy the birds, the little crabapples will be very inviting through the winter time!
If you are selecting a new flowering crab, you can select one that doesn't produce fruit, or if you want the fruit, you can select one that retains the apples well into winter. Stop by the Extension Office and ask for the flowering crab bulletin to help you select the variety. You may also want to be careful not to plant one of these trees where they will hang over a driveway, sidewalk or patio to reduce the number of apples, or other deposits, that you may have to deal with.
But, if you really don't want those little apples there is a way for you to greatly reduce the amount of fruit on your tree. There are some sprays that can be applied that cause the little apples to fall off. You may be able to find products on the shelf of your local garden center specifically for this chore, but if not start checking the bottles of Sevin (carbaryl) to see if they mention fruit thinning.
It is important to wait until just after the tree is through blooming. Sevin is very toxic to honeybees and you don't want to spray the tree while bees are still visiting the blossoms. As soon as the blossoms have all dried up, mix two tablespoons of Sevin per gallon of water and thoroughly spray the tree. Stems of the small fruit should start to turn yellow and wrinkle and the apples should start to drop seven to ten days after spraying. If drop hasn't started in two weeks a second treatment may be needed. The longer you wait after blooming, the harder it will be to get the fruit to drop.
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