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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
Varietal Preference of Leafhopper or Varietal Susceptibility 
to Disease or Both 
Different varieties of potatoes were attacked to different degrees by 
the potato leafhopper, and different varieties were affected to different 
degrees by the disease. The extent to which the same varieties were 
affected appeared to be much the same at widely separated points in 
the state. The Early Triumph variety was always affected worst; 
the Rural New Yorker variety always least and, moreover, in a given 
place, the Rurals were always attacked least by the leafhopper. The 
relative infestation on other varieties varied considerably. 
It is believed that the leafhopper exhibits a preference for certain 
varieties of potatoes of tender foliage and that these same varieties may 
be more susceptible to disease than sturdier varieties of hardier foliage. 
Plants of a Given Variety Vary Greatly in Amount of Disease 
Observations the past season have shown that certain plants of one 
variety may have much greater resistance to disease than adjacent 
plants of the same variety. In a check (unsprayed) plot of Rural 
New Yorker potatoes three plants remained practically free of disease 
all summer, while the surrounding plants without exception became 
badly diseased. The same was true of a plot of Green Mountains. 
Effect of the Disease on the Tuber 
There are indications that the disease transmitted by the potato 
leafhopper seriously affects the potato tuber. Whether the actual 
organism of the disease gains entrance into the tuber, or the diseased 
foliage decreases the value of the tuber for seed, is yet to be determined. 
It can be stated, however, that plants of the same variety but from 
different seed, growing side by side, exhibited decided and uniform 
difference in the amount of disease present. This difference was 
noted in two instances at one farm; two fields of Green Mountains 
were planted in blocks, each block being the seed from a different 
grower. All potatoes in each field were planted the same date. The 
degree to which plants in adjoining blocks were affected with disease 
enabled one to separate the blocks without looking at the end stakes. 
In one field at Madison six varieties of potatoes were planted. 
Seed of five of the varieties came from reputable seedmen, and the 
plants treated with Bordeaux mixture stood off the disease throughout 
the summer. The sixth variety, Early Triumph, was seed from plants 
which had been killed by the disease the year before (1918). The 
plants from this seed were all killed by the disease early in the season 
despite thorough treatments with Bordeaux. 
Is it possible that some condition due to disease may be carried over 
