Spraying Experiments in Nebraska 
49 
the flower buds began to ?how pink and lasting until after the 
petals had fallen. Evidently there was also considerable infection 
during the period between the 14-days and the 21-days spray. 
The fact that all the plats in table 32 are consistent in showing 
less scab infection than the corresponding plats shown in table 
31 is conclusive evidence of a late secondary infection which 
occurred at such time that the August spray controlled it to a 
great extent. 
INCIDENTAL OBSERVATIONS 
During the past three seasons a number of observations were 
made which were not scheduled in the regular plans. 
In securing the records, it was noted that there was consider- 
able consistent variation in the amount of infection on different 
varieties of apples. This led to a study of all the available varie- 
ties, to determine which, if any, were resistant to scab. After 
three seasons of this work, it was found that the records of a vari- 
ety for one season did not always correspond with the records of 
the same variety for another season; e. g., the variety Winesap is 
usually considered much more susceptible than Ben Davis. The 
records bear this out for 1913 and 1914, but in 1915 scab was, in 
many instances, more prevalent on Ben Davis apples than on 
Winesap. On the average perhaps this is not true. It was also 
found that none of the common varieties are entirely free from 
scab, altho many varieties exhibit a great deal of resistance. On 
comparing observations made with the results previously reported 
by other workers, this variation in susceptibility is emphasized. 
Wallace (1913) makes a similar statement and quotes extracts 
from other publications. 
From the observations made in various orchards in the State 
and in the variety orchard at the Experiment Station the va- 
rieties have been tentatively grouped as follows : 
Practically resistant Moderately resistant Susceptible 
Wagner Jonathan Arkansas (Mammoth 
Oldenburg (Duchess) York (Imperial) Blacktwig) 
Wealthy Ben Davis Ralls (Jenet) 
Patten Greening Windsor Northern Spy 
Gano Red June 
Grimes (Golden) Virginia Beauty 
Missouri (Pippin) Yellow Transparent 
Salome Sheriff 
Champion Maiden Blush 
Minkler Walbridge 
(1913) Vv'allace, Errett. Scab disease of apples. Illinois Sta. Bui. 335:579-582. 
