36 MISC. PUBLICATION 161 



mon on apples and pears. The rots they cause are usually firm and 

 vary in color from light to dark brown, but are not readily dis- 

 tinguishable from one another except by laboratory study. No 

 attempt will be made to describe them here. (68. 76, 8S, 100, 116, 131, 



132, 167, 169, 199, 200.) 



PANSY-SPOT INJURY 



Pansy spots are white or greenish areas a half inch or more across, 

 which are frequently lobed in such a way that the outline suggests 

 the shape of a pansy flower (pi. 19, G). They are caused by the 

 flower thrips {Frankliniella tritici Fitch) and probably by other 

 species of thrips. At the centers may be found greenish-brown corky 

 spots, seldom more than an eighth of an inch in diameter, which 

 develop around the punctures made by the female thrips in the proc- 

 ess of Qgg laying. The spots show conspicuously on green immature 

 apples and often become prominent and serious defects at harvest, 

 on the Mcintosh variet}^ in particular, when the red color (in the 

 spots) seems to be permanently lost. On some other varieties the 

 spots may become quite inconspicuou-S as the natural coloring of the 

 fruit develops. Evidence has been obtained that the spots do not 

 enlarge or change in any other way while the frifit is in storage. 



Partial control may be obtained by spraying the trees when in 

 full bloom with nicotine sulphate (40 percent nicotine) in the pro- 

 portion of 1 pint in 100 gallons of water, with the addition of 

 enough soap to make the solution soapy to the touch. A casein 

 spreader may be used in place of soap. The addition of nicotine 

 to the calyx spray is also helpful in controlling the thrips. {Jfi, 163,) 



PEAR-LEAF BLISTER-MITE INJURY 



(See Pears, Pear-Leaf Blister-Mite Injury, p. 53) 



PHYTOPHTHORA ROT 



{Phytophthora sp., probably P. cactorum (Leb. and Cohn) Schrot) 



Phytophthora rot is a parasitic disease of apples and pears and has 

 been found in fruit from New York, Connecticut, Michigan, Indiana, 

 Washington, and Idaho. So far as known it does not cause heavy 

 damage in any of these States and it is not common on the market. 

 The varieties of apples found affected on the market are Twenty 

 Ounce, Tolman Sweet, Baldwin, Winesap, Jersey Sweet, Wealthy, 

 Gideon, Ehode Island Greening, Tompkins King; of pears, Clair- 

 geau, Kieifer, Bosc, Howell, Bartlett, Anjou, Angouleme. Doubt- 

 less other varieties of both kinds of fruit are sometimes attacked. 

 The rot is able to develop slowly at cold-storage temperatures, but 

 there is no evidence that it can spread from affected to sound fruit, 

 either in transit or in storage. 



Phytophthora rot on apples as seen from the outside is light brown 

 in color (pi. 4, A) ; on pears it is dark brown to black. In both 

 apples and pears there is always a marked browning of the bundles 

 or strands that conduct food and water through the fruit. This 

 browning occurs in the large bundles near the core and the smaller 

 ones throughout the flesh, and from the former may even extend 



