THE TERRAPIN SCALE. 67 



April and May, and another in July from the leaf -attached larvae; 

 but neither of these deposits is sufficient to do much damage. The 

 really important deposit starts about August 10, at the time when 

 the females attach to the twigs, and continues until the approach of 

 cold weather. The amount of sooty mold produced is limited 

 apparently only by the amount of honeydew excreted. The mold 

 becomes noticeable during the first week in July as black streaks 

 which first appear in the depressions on the upper surface of the 

 leaves. It gradually increases in amount until the middle of August, 

 and from this time until the middle of September the increase is 

 very rapid. The infestation is at its worst about the middle of 

 September, at which time fruit, foliage, and branches are covered 

 with a sticky black slime. The extent of the injury depends upon 

 the degree of infestation and upon the time of ripening of the fruit. 

 Late varieties are damaged most by the mold-infested honeydew, as 

 it shows worse upon fruit which ripens after the middle of August. 



REMEDIAL MEASURES. 



At the beginning of this investigation lime-sulphur was known to 

 be ineffective and kerosene emulsion was considered unsatisfactory in 

 the control of the terrapin scale. The so-called miscible oils (pro- 

 prietary emulsifiable oils), however, were believed to be reasonably 

 efficient when properly employed, though it was believed that there 

 was more or less danger to the trees and fruit buds from their use. 



For convenience in treatment the materials used in these experi- 

 ments are considered in groups. In all 62 experiments were per- 

 formed, most of them in the orchard of D. M. Wertz, at Mont Alto, 

 Pa. The others were at Midvale, Pa., and at Washington, D. C. 



A consideration of the life history of this scale shows that it can 

 be attacked both in the larval and the adult stages. The adult stage, 

 owing to its long duration and accessibility, obviously offers the more 

 favorable opportunity for treatment. During the first season spray- 

 ings were made against both the larva and the adult. 



OIL SPRAYS. 



Experience shows that all oil sprays are most effective when 

 applied as a fine mist and under strong pressure. All oils were 

 applied with disk nozzles of the Vermorel type, having apertures of 

 one-sixteenth inch. The oils noted in Table XXXVIII, all of which 

 were applied in the spring after the buds had started to swell but 

 before they had opened, proved to be inefficient. These oils were 

 emulsified as follows: 



Oil 2 gallons. 



Soap (hard) § pound. 



Hot water 1 gallon. 



