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-37 UNITED STATES DEPARTMENT OF AGRICULTURE. 



">? BUREAU OF ENTOMOLOGY, 



WASHINGTON. D. C . 

 FOREST ENTOMOLOGY 3 



, April. 3. 1916* 



Brief Information on 

 SCALE INSECTS ON SHADE TREES and HARDY ORNAMENTALS 

 and REMEDIES EMPLOYED AGAINST THEM. 



Appearance and habits.- Scale insects are so-called because of the scale that 

 covers or constitutes the back of most of them. This scale may be horny, 

 leathery, waxy? cottony or mealy and just as various in size, shape and color. 

 There are many species of scale insects and, according to the consistency of 

 the scale, they are roughly divided into armored (horny), soft (leathery), 

 cottony scales, mealy bugs, etc. Except for a few days after hatching, when 

 they are naked, these insects are always covered by the scale characteristic of 

 the species to which they belong. The number of generations annually, date of 

 hatching and other life habits vary with the species, season and location. They 

 are all plant feeders, some confining themselves to a single species of plant 

 while others occur on a great variety of plants. They occur on the main stem, 

 branches and twigs; some of them also on the leaves and fruit in summer. They 

 feed on sap which, by means of the needle-like beaks, they suck up from within 

 the plant tissues and are, therefore, classified as sucking insects. Some 

 of them produce more or less honey dew which attracts ants, bees, wasps etc., 

 which eat it but do not harm the plants. This honey dew frequently results in 

 a sooty appearance of the affected plants. 



Natural control.- With very few exceptions, scale insects are usually kept in 

 check by a variety of natural agencies, especially parasitic and predaceous 

 insects. As a rule, therefore, they do no permanent, serious harm and require 

 no remedial treatment. .Occasionally, however, some species are apt to become 

 so numerous as to be very injurious. Treatment then is warranted, if otherwise 

 practicable. 



Remedies.- (See accompanying brief on Scale Insect Remedies,) 



Being sucking insects, scale insects cannot be killed by means of stomach poisons. 

 They are controlled mostly by being covered at the proper season with a liquid 

 substance which, without injuring the plant, kills the insect by either clogging 

 its breathing pores or penetrating to its vitals, or both. The aim must, there- 

 fore, be to cover every individual insect. The covering is affected by 

 means of a spraying device which may be a tin atomizer, a bucket, knapsack or 

 barrel sprayer or a power spraying machine, depending on the extent cf spraying 

 contemplated. 



Winter Spraying, done when the buds are dormant, is preferable because (l) there 

 is then no delicate foliage to injure and none to conceal insects or to use up 

 spray; (2) dead and superfluous portions of the plant may and should then be 

 removed, still further reducing the area to be sprayed and exposing the in- 

 sects,; (3) plants are then dormant and can withstand stronger sprays without 

 in j ury . 



Summer Spraying, when imperative, is most effectively done when the young are at 

 the height of hatching (crawling about in numbers). 



A. D. HOPKINS, 



Forest Entomologist. 



