292 OHIO EXPERIMENT STATION: BULLETIN 332 



Nature of work. The needles only of the host are attacked 

 and where the infestation is only moderate no very serious results 

 attend the presence of the pest. When the attack is severe, the 

 needles become yellow and parts or the entire tree may die. It is 

 not very common, however, for the attack to end fatally. 



Food plants. The following conifers have been recorded as 

 hosts of the pine scurfy scale : Pinus strobus, P. resinosa, P. ex- 

 celsa, P. mitis, P. cembra, P. pyrenaica, P. laricis, P. sylvestris, P. 

 austriaca, P. pumilo, Pseudotsuga taxifolia,, Picea excelsa, Picea 

 nigra and Picea alba. 



Distribution. This species abounds throughout the State, par- 

 ticularly in and near towns and cities. Its range extends to embrace 

 practically all of the states of the northern section of the Union 

 but it is most prevalent east of the Mississippi River. 



Natural enemies.^Two parasites, Perissopterus pulchellus and 

 A^lfielinus mytilaspidis have been reared from this species. The 

 following list of predators has been reported as preying upon it: 

 Chilocorus bivulnervis, Scymnus sp., Cocinella picta, Chrysopa sp., 

 and Cybocephalus nigritulus. 



Control. Our present knowledge of control methods for this 

 species is in a rather imperfect condition. Doubtless the normal 

 winter strength of lime-sulphur wash or miscible oil would prove 

 effective against the scale when applied during early spring, as has 

 been done in the writer's experience, but neither are recommended 

 at this time because of probable injury to the host. While the few 

 white pines which the writer sprayed with these materials were not 

 injured by the treatment, the test was not sufficiently comprehen- 

 sive to warrant general conclusions. It is possible that of the two 

 classes of materials, the sulphur sprays would be less likely to cause 

 injury since it is generally considered that conifers are intolerant 

 to oily mixtures. On one occasion, in 1903, the writer sprayed a 

 large number of pines on the Ohio Experiment Station campus, 

 using weak kerosene emulsion in May when the young of the spring 

 brood were hatching; in late summer an application of whale-oil 

 soap was made to the same trees when the young of the summer 

 brood appeared. The combined treatment effectually reduced the 

 infestation and it is likely that summer spraying is the safest con- 

 trol measure to be used against this species. No definite dates can 

 be given when the spraying should be done, since the time of the 

 appearance of the young varies with the character of the season. 

 The infested pines should be watched and .when the brood of crawl- 

 ing young appears, the spraying should be done. The first brood 



