Page:Growing Black Locust Trees.djvu/24

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In midsummer or early fall the foliage of black locust trees often turns from its usual light green to a grayish brown. A close examination will show little left but the veins or skeletons of the leaves. The green portion, or chlorenchyma, has been eaten by an insect known as a locust leaf miner. The most common species in the Eastern States is a sawfly (Odontota dorsalis) but there are known to be one or more closely related insects that mine the green in the leaves. The effect is to retard the growth of the tree slightly, but nothing more serious. It is not practicable to attempt to check the insect.

In addition to the usual care needed by trees planted for timber production or windbreaks there are some points in handling black locust that are effective in reducing the attack and injury of harmful insects, particularly the locust borer.

Important practices in the care of young stands, that will pay well, all center around keeping the growth thrifty and vigorous. For reducing the borer attack the following practices are to be recommended.:

(1) Choose favorable soils or locations for planting black locust. This is most important in localities of bad borer infestation but should always be kept in mind.

(2) Prepare the soil thoroughly so as to make a good planting bed in which it will be easy for the lateral roots to spread rapidly. Often, fair to good success has been attained by planting locust in poor or sterile soil that was well plowed or disked in advance of planting. There are insufficient data on which to base any general recommendations for adding fertilizer to the soil at the time of planting. However, experiments in adding a teaspoonful of commercial fertilizer, containing nitrogen, phosphoric acid, and potash, have shown decidedly good results in stimulated vigor during the first 2 years. The cost per acre has been reported as not more than 60 cents. Some soils require only acid phosphate.

(3) Cultivate the planted tract well for at least the first season after planting. It would be better to continue cultivation during the second year. If this is not practicable, weeding and cultivation around each tree will prove very beneficial. A mulch of straw, leaves or other vegetable matter around the tree will help in holding needed moisture and keeping the soil loose. In the Great Plains cultivation is very essential and should be kept up for a much longer period.

(4) Increase the protective ground cover to maintain vigorous growth of the trees. The black locust makes only a light shade and a thin leaf litter over the surface of the ground. Therefore the soil dries and hardens, becoming unfavorable to good rates of growth. It is therefore very desirable to interplant locusts with other trees that have heavy foliage and that are also slower growing so as not to overtop the locusts. After the young trees reach a height of 8