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UT\TITED STATES DEPART-MENT. OF AGRICULTUBE- 



;a 16 1956 ★ 



/5J \ 



. - . ' • . BUREAU OF - ENTOMOLOGY ^^>?'. 



. -; . ■ ■ 'T^ashington, D. C. 



Forest Entomology- Brief ' yg/ - ■ May 1, 193^ 



GENERAL INFORMATION ON SCALE INSECTS THAT 

 ■ ATTACK SHADE TREES AND HARDY SHRUBS 



There are many species of scale insects that infest shade trees and 

 hardy shrubs. Scale insects may he so called for two possible reasons. One 

 reason is that in some cases they are small, abundant, closely attached to 

 the plant, frequently tend to overlap, and usually flake off easily; they 

 thus lend the portion of the plant attacked the appearance of being cov- 

 ered by scales. The other reason is that in the case of many of these in- 

 sects the actual body of the insect is covered and protected by a secreted 

 scale, plate, or scab. This "scale" may be horny, leathery, waxy, cottony, 

 or mealy, and may also differ in size, color, and shape for each species. 



Scale insects feed by sucking juices from the -plant attacked , through 

 a slender, hairlike beak which, protrudes from the under side of the head. 

 Usually the young scales, or "crawlers", locate on the smooth bark of small 

 branches and twigs, but occasionally they attack leaves. They are also 

 found sometimes on the bark of the trunk and larger limbs of trees, and even 

 on the fruit and roots. They probably are vigorous feeders, for trees at- 

 tacked by them in abundance usually show decided signs of decadence, and 

 leaves, twigs, branches, and even entire trees may be killed, and freaueritly 

 are seriously weakened and injured. 



Scale insects attack a wide variety of plants. Some species of scales 

 axe rather restricted in the number of kinds of plants that they can or 

 will use as hosts, while other species are injurious on quite a variety of 

 different plants. 



^Locomotion in the scale insects is almost entirely confined to the very 

 young insects. These young scales are minute and generally yellow in color. 

 They crawl about on the plant for a short period after hatching from the egg 

 or leaving the female. Very soon, within a few days, these young scales, or 

 "crawlers", affix themselves in a favorable location and begin to feed. About 

 the only other movement in the life of scale insects occurs when the adult 

 male develops wings and emerges from the scale to fly about seeking a mate. 

 The adult female scale insect remains fixed in the feeding location. 



COIvIBATING SCALE INSECTS 



The control of scale insects is rather difficult, owing especially to 

 the protective scalelike covering they frequently develop after the crawling 

 stage. Since they suck joices from the plant when feeding, a contact in- 

 secticide is generally used to combat them. 



(over ) 



