OCR Text |
Show ENTOMOLOGY Edited by Prof. E. G. Titus, State Agricultural College. If you do not find here what you want to know, write for it. THE EUROPEAN ELM SCALE. This is, in our state, the most common com-mon scale insect attacking the elms, It occurs on elm trees in a number of places, including Salt Lake, Og-den, Og-den, Provo and Kaysvillc and in several sev-eral places some trees have been killed outright and others scvcrcly.jn-jurcd. scvcrcly.jn-jurcd. The elm a3 a shade tree far surpasses sur-passes the cottonwood or box-elder. It is a highly valuable tree, not only from the standpoint of practical utility, utili-ty, but also as an ornament to our yards, streets and highways, or these reasons it behooves us to keep a close lookout for its enemies and to protect it wherever we can. The European Elm Scale (Gosjsy-paria (Gosjsy-paria souria Mod.) was first observed in the United States in 1884 at Rye, New York. It has since spread to a number of statc9 and has been reported re-ported as seriously injurious in several sev-eral places. In the West it has done considerable damage at Spokane, Washington, and in several places in Nevada. Dotcn reports it as haYjng been present in Nevada for at least fifteen years and now spreading rapidly. rap-idly. Like all scale insects it belongs to the Hcmiptcra, one of the groups in which all the members have 3ucking mouth-parts. This particular specic9 hibernates in the young larval stage The small larvae appear quite grey in color and may be most easily de-tcctcd de-tcctcd by scraping the bark with the finger nail. This treatment crushes them and leaves on the bark and finger fing-er a tiny red streak. The most of the hibernating larvae may be found on the- underside of the rough bark of the larger branches, but they also occur scattered over twigs, on buds, leaf-scars, leaf-scars, around bases of small twigs and often beneath the cocoons of dead females. fe-males. The young larvae remain in tlieir hibernating quarters until early spring when they complete their growth. The small elongate cocoons of the young males are pure white and wjien clustered on smooth bark are con spicuous objects, in cases of severe infestation in-festation being visible for some distance. dis-tance. The male insects come from the cocoons in late March or early April and may be cither wingless or winged. The females become mature at about the same time or a little later lat-er and may be found in May gathered in great numbers on the underside of the lower branches. The insect at this time is a deep brown with a white waxen ring surrounding her. During the egg-laying season (June and July) many of those scattered over the other parts of the tree may be seen. Their bodies become crowded crowd-ed with hundreds of eggs. The eggs arc oblong, pale yellow, and about eighty of them placed end to end would make an inch, they arc abouc one-half as wide as long. The newly-hatched larvae arc bright lemon-yellow and may be seen crawling crawl-ing slowly about the bark anJ leaves (often a hundred or more on a single leaf) seeking a place to settle down and suck sap for the rest of their life. Here they remain until the next spring. When the infestation is very heavy the leaves will sometimes fall and then those that have not permanently per-manently settled will often leave the leaves and crawl onto the trunk of the tree or to another tree. As with all other insects producing large numbers of young each year, en immense number perish before reaching maturity. Many of them fail to hatch, many do not get properly located and many more die before spring from other insect fatalities; while a large number arc destroyed by their enemies, both bird and insect. in-sect. Were this not so their excessive multiplication would soon kill all the elms and the loss of their food plant would cause their own annihilation. The spread of the insects from tree to tree and locality to 'ocality is accomplished ac-complished in sevenu vays. Young elms containing the hibernating larvae lar-vae may be shipped from an infested loc-vlity. Insects that alight upon the tree may carry some of the young larvae on their feet and birds may accomplish the same act; thus the insects in-sects might easily ibe spread for many miles. Trees growing too closely together to-gether will allow the latvae to pass from one tree to another and thus aid in distribution. Blowing leaves will carry larvae from tree to tree along the ground and some of these larvae may succeed in reaching a feeding place. Remedies. Some cultural methods are essential, essen-tial, yes even vital, to the means ol control for this scale-insect. Remove ail water sprouts and burn early in the year and throughout the summer and fall. Trim trees right, do not allow two trees to have their branches interlacing. in-terlacing. Do not plant too thick, that is too close together, it weakens the trees and affords an exceptionally easy means for the larvae to pass from tree to tree. The scale flourishes flourish-es in crowded and neglected elms. Burn up the leaves on the ground. In pruning trees do not leave unsightly un-sightly stubs, cut close to the larger branch or trunk from which you are removing the limb. The stubs are hard to spray. The question of remedies has lately been discussed in an excellent bulletin from the Nevada Station, written by the Entomologist, Prof. S. B. Doten. Besides giving a thorough account of the life-history as it occurs in that state he has written up an account of his experiments for one season. I had the pleasure last spring of visiting visit-ing at Reno and seeing the work of the scale in that city and some of the spraying results accomplished by Prof. Dotcn. He summarizes his work by stating that while lime-sulfur is probably the best spraying mixture mix-ture to be used it is wall to use some other precautions. He advocates the thorough washing of the tree before spraying to drive off, by the force of the water, the clusters of dead females. fe-males. This will enable the spray to reach the hibernating larvae that otherwise would have remained clustered clust-ered and protected beneath these female fe-male cocoons. Prof. Dotcn also says, "wash down with a stiff stream o'f water under high pressure, late in May or early June to destroy the living female fe-male insects which escaped the action of the insecticide." Without doubt these precautions will be of service and the householder in the towns having water service can avail himself of this means to aid in controlling the scale, but he should by no means attempt to control by this means alone. Spray with lime-sulfur lime-sulfur as late in the spring as possible and spray thoroughly; cover every particle of the trunk, driving the spray into all the crevices of the bark; see that each branch and limb and twig is thoroughly coated with the mixture and then use every other means in your power to protect your trees. A kerosene emulsion spray (1-15 formula) formu-la) may be used to advantage when the young larvae arc first crawling in early summer, but since they arc hatching hat-ching over a considerable period and many crawl to the leaves it can only be a partial -control. Look your elms over NOW; examine ex-amine the leaves on the ground, if there arc leaves on the trees, dead hunches hanging on the twigs, examine ex-amine these twigs and leaves thoroughly; thor-oughly; look on the underside of the larger limbs and in the crevices of bark on the trunk. If you find the scale prepare to get after it and treat it well, that is give it a good thor-1 thor-1 ough coating with the best lime-sul phur you can make. 0 |