372 JOURNAL OF ECONOMIC ENGOMOLOGY [Vol. 15 



Cost of dusting per tree 



Amount of dust per tree 



Amount of spray per tree 



Net returns from one spraying per tree 

 " " " " dusting " " 



" " " " spraying " acre 



" " " " dusting " " 



Net difference per acre in favor of spray 



TWO INJURIOUS FRUIT MITES IN PENNSYLVANIA 



By S. W. Frost, E?it. Research Laboratory, State College, Pa. 



Two mites have been found injurious on fruit trees in Pennsylvania. 

 One is the European Plum Mite, Paratetranychus ptlosus Can. & Fran., 

 which was previously recorded in the Journal^ as a pest chiefly on apple 

 and plum although it occurred to some extent on cherry and peach. 

 A second mite, Phyllocoptes cornutus Banks has recently been found very 

 abundant in parts of the state on peach. This species was first noticed 

 in Cumberland county, Pennsylvania, in 1921, by Mr. W. A. McCubbin, 

 Deputy Director State Bureau of Plant Industry, Harrisburg, and was 

 thought at first to be a silver leaf resembling closely the European 

 silver-leaf disease. Further examination and a consultation with an 

 entomologist has identified the injury with that of a small mite which 

 Mr. Nathan Banks has previously described and recorded from this 

 country. It has also been found in Lebanon, Dauphin, and Adams 

 counties and further examination will no doubt reveal its presence in 

 other parts of the state. 



Both species produce characteristic injury upon their hosts. The 

 European Plum Mite causes the leaves to turn yellowish and later be- 

 come bronzy in color. The silver Leaf-mite of peach causes the leaves 

 to become silvery and later become leaden in color. Both species have 

 a tendency to flatten the leaves so that the appearance from a distance 

 is very different from the normal foliage. 



Scientific Notes 



Aroostook Potato Insects^. Since aphids have been found to transfer potato mosaic 

 and leaf roll (Bulletins 292, 297, and 303 Me. Agr. Exp. Sta.), and certain other 

 insects with piercing and sucking mouthparts are being viewed with suspicion, 



ijourn. Econ. Entomology. Vol. 12, pp. 407-408, 1919. 



^Papers from the Maine Agricultural Experiment Station: Entomology No. 111. 



