EXPERIMExXT STATION BULLETINS. 



339 



Fig. 63. — Apricot Scale, on plum, enlarged four and one-half times. Author's illustration. 



material in which the eggs are deposited The winter is passed while they are 

 still soft and but partially grown. This fact gives us one method of controlling 

 them. The pest works also on grape and cherry besides several other plants. 



KEMEDIES. 



Take advantage of the soft and unprotected condition of the creature during 

 the winter and apply one of the strong winter sprays recommended for the San 

 Jose scale, either lime-salt and sulphur prepared in the ordinary way, or kero- 

 sene-emulsion in which the water forms about one-tifth of the liquid when ready 

 to be applied. 



ATFECTING THE FOLIAGE. 



Plum Aphids. (Phorodon humili, OjiJiis priini et al.) 



Several species of plant-lice Infest the plum, the two most important being the 

 true plum-louse (A. Pruni), which remains on the plum all the year round; and 

 the hop-louse (P. Jiumuli) . This latter species is restricted to regions where 

 hops are grown, as a matter of course, and migrates, back and forth between the 

 two host plants, spending the summer and early fall on hops, and late fall, winter 

 and spring on cultivated or wild plum. In other words the eggs are laid on the 

 plum branches in October to hatch out the following spring. The young lice 

 which are at this stage provided with wings, migrate to the hop yards for the 

 summer, their progeny coming back to winter quarters in the fall. The true 

 plum-louse remains the year round on the plum trees, curling the leaves and 

 sometimes doing considerable damage. 



REMEDIES. 



The ordinary spray of kerosene-emulsion, or tobacco-water, will kill the lice 

 easily enough if they can be reached. Very thorough work in the central part 

 of the tree is required to hit them because of the curled condition of the leaves. 



The Plum-tree Sphinx. {Sphinx drupiferarum.) 



The hawk-moths seldom occur in sufficient numbers to seriously affect our 

 fruit trees. Occasionally the plum foliage is attacked by large, green caterpillars, 

 each having a curved horn or spike projecting from the caudal end and with 

 the body marked by seven short diagonal stripes of purple on each side, each 

 stripe being bordered beneath with a narrow stripe of white. These are the larvas 

 of the plum-tree sphinx. When full grown, they burrow into the ground and 



