24 



HARMFUL INSECTS AND THEIR CONTROL 



To act intelligently in the control of insect plant pests, we must 

 remember that they are divided into two general classes, accord- 

 ing to their habits of attack on the plant. 



The sucking insects, including the scales, spiders, mites, plant 

 lice, squash bugs, etc., obtain their food by inserting their pro- 

 boscis into the tissues of the plants and extracting the sap, caus- 

 ing insufficient nourishment to the plant leaves, shown by pale or 

 drooping foliage. 



The biting insects have jaws similar to ours, but which work 

 sideways, and they take portions of the masticated leaves and 

 other plant tissues directly into their stomachs, often defoliating 

 portions of the trees and tunnelling the bark and even the wood. 

 They include the grasshoppers, leaf-eating beetles, and the many 

 forms of moth, beetle and butterfly larva, known as cut-worms, 

 grubs, wireworms and caterpillars. 



The biting insects can be poisoned either by arsenical sprays 

 (Paris Green or Arsenate of Lead) put on the foliage of the plants, 

 or by similar poisons in tempting food, like dampened bran, or 

 some kind of green food placed near their haunts. 



The sucking variety can be killed either with sprays, which kill 

 by coming in contact with their bodies, or poisoning the air about 

 them, or smothering them by closing up their breathing places, 

 usually a row of holes along their sides, called spiracles. 



The kerosene or distillate or caustic emulsions act in the first 

 mentioned manner, fumigation the second, while resin wash closes 

 up the spiracles. 



The Black Scale 



(Saissetia oleae) 



The Black Scale (Saissetia oleae) is probably the most widely 

 known and constantly fought of any scale of the citrus tree, and 

 is usually pretty well known in the adult stage. It is black, or 

 nearly so, and has cross ridges on its back in the form of the letter 

 H, by which it can easily be distinguished from the Hemispherical 

 and other scales of the same family. 



