New York Agricultural Experiment Station. 377 



diseased potatoes are planted the fungus spreads to the stems and 

 leaves and there manifests itself in the dark brown withered parts 

 of leaves or stems. It sends out mildew threads, commonly on the 

 under surface of the leaf, and there produces spores wliich may be 

 called the seeds of the disease, and which are distributed by wind 

 and rain, thus spreading the infection. In warm, moist weather it 

 spreads most rapidly, in fact so rapidly that fields where the dis- 

 ease is present are frequently said to be " struck with the blight," 

 so sudden, apparently, has been its attack. The disease also spreads 

 to the tubers, and thus attacking both vines and tubers it may occa- 

 sion very serious loss. If conditions are favorable it may spread 

 rapidly early in the season but more commonly in this State it 

 appears to do most damage after midsummer. 



Remedies — Spraying for blight should be begun when the plants 

 are six or eight inches high. Three and four sprayings with Bor- 

 deaux mixture, 1 to 7 formula, making the first treatment as just 

 stated and others at intervals of about two weeks, have been suffi- 

 cient here to control this disease, and also the one next described. 



Macrospoeium. — This disease, caused by a species of black mold, 

 has been called by some " Early Blight," because it is commonly 

 found on early potatoes. It makes its appearance usually in June, 

 and attacks the foliage. It may be known by the peculiar spots 

 that it produces on the leaves. These have been described as target- 

 shaped marks from the fact that a number of circles surround a 

 common centre in such a manner as to represent a target in minia- 

 ture. The affected portions of the leaves become dry and crisp. 

 The disease spreads slowly, and has not been known to be as injuri- 

 ous in this section as the blight first mentioned. The same treat- 

 ment is used for this trouble as that given above for the blight. 



Potato Scab. — This disease is confined to the tubers, so its 

 attacks are not noticed until the potatoes are dug. It causes the 

 outer portion of the potato to become pitted, rough and corky, or 

 " scabby." In some localities this condition is thought to be caused 

 by the larvae or grubs of the May beetle ; hence the name " grubby 

 potatoes" is applied to them. But the attacks of the grubs are 

 local, and their work can be told from the fact that they eat out 

 rather deep grooves or furrows in the surface of the potatoes. 



Remedies. — Since this disease does not appear on any part of the 

 plant above ground, any spray applied to the vines would be useless. 

 The only way then to combat it is to improve the sanitary con- 



