280 INSECTS AFFECTING VEGETATION 



sap, hence applications of poisons are ineffective, and for all practi- 

 cal purposes it may be said that control methods are confined to 

 spraying with contact insecticides during one or both of two sea- 

 sons, the latter depending upon the species. Some scales are more 

 easily destroyed by the action of a strong spray, used during the 

 winter months, while others are susceptible to treatment with a 

 weak spray applied during the summer months when the brood of 

 young is appearing. The last named method, however, is useful 

 only when the entire brood of young appear within a few days, and 

 when the host is foliated sparsely enough to permit the spray to 

 reach all parts of the plant. 



The Oyster-shell Bark Louse* (For a complete description, 

 see Insects Affecting the Apple). In appearance this scale is dark 

 brown in color, shaped like an oyster shell, and is about one-eighth 

 inch in length. 



A number of plants are quite susceptible to this scale, the most 

 common for Ohio being Carolina and Lombardy poplar, willow, 

 horse chestnut, ash, sassafras, and red-twigged dogwood. The pop- 

 lars are undoubtedly the most susceptible of all, and so injurious in 

 fact is this scale to these trees that the authorities in Cleveland have 

 stopped the planting of them, and wherever practicable are replac- 

 ing growing trees with more desirable kinds. Spraying during the 

 early spring with the lime-sulfur wash, or during the hatching 

 period with kerosene emulsion or whale oil soap solution, is the 

 remedy usually employed against this pest. 



The San Jose Scale. (For a complete description, see Insects 

 Affecting the Apple.) This species is almost well enough distrib- 

 uted and well enough known to render a description unnecessary. 

 However, it may be stated briefly that the individual scales are very 

 flatly conelike, with a whitish nipple at the apex ; the remainder of 

 the scale is gray or blackish and the whole is about the size of a 

 pinhead. When occurring in large numbers on a branch it gives 

 it a gray ashy, flaky appearance. The more common of the plants 

 suffering seriously are as follows: juneberry, hawthorn, privet, 

 poplar, Prunus spp., currant, apple, rose, willow, ash, lilac, osage 

 orange and elm. A winter application of the lime-sulfur wash is 

 the safest, most effective and cheapest remedy for this pest. 



The Scurfy Bark Louse. This insect appears in the adult stage 

 as flat white specks upon the bark or fruit of the host. The winter is 

 passed in the egg stage under the protecting mother scale, hatching 

 occurring during the latter part of May or in early June. The red- 

 twig dogwood, willows and some of the rosaceae are particularly sub- 

 ject to such infestation. The lime-sulphur wash applied during the 

 winter is effective, as are also contact sprays applied at hatching time. 



The Putnam Scale. On account of similarity in general form 

 this species is frequently mistaken for the San Jose Scale, especially 

 when the infestation is slight and the scales immature. The super- 

 ficial distinguishing features however are as follows: the scale is 

 slightly darker in coloration ; the nipple reddish ; the spread less 

 rapid ; the injury less severe, and lastly the young exhibit a stronger 



* See illustration on page 375. 



