Field Observations on Development of Potato Blight 197 
far end of the Dunbar bed about 100 yards away from the area first 
affected. 
At this date the disease was not found in any other potato 
areas in the immediate vicinity of Plot 2. 
As in Plot 1, this outbreak of the disease in epidemic form was 
was very circumscribed in area and was preceded by the appearance 
of discolouration on a stem of one of the plants in the infected 
area. It is noteworthy that when the fungus was first found 
fructifying in the field it was on this plant that it was most 
abundant. 
Although careful search was made, no shoots from last year’s 
blighted tubers bearing Phytophthora were found but strong 
suspicion was aroused that these blighted tubers had something to 
do with the outbreak, though in what way could not be ascertained. 
These blighted tubers may have sent up diseased shoots 
hearing spores, which escaped detection, or they may have been the 
means of introducing resting spores into the plot. It is 
significant that for some time the only plants affected in the plot 
were those within the limits occupied by blighted tubers of the 
previous year. The occurrence of typical blight spots on the 
leaves at the same date as these were observed in Plot 1 is 
probably to be correlated with the incidence of similar weather 
conditions. 
No report of the appearance of Phytophthora in epidemic form 
in other parts of the Isle of Wight was received until July 28th 
when it appeared at Whippingham, a few miles from Haven Street. 
At Whitwell, 10 miles away, I was informed that the disease 
was seen during the last week of July on the leaves of a single prostrate 
plant (Sharp’s Express, an early variety) growing under very moist 
conditions, but blight did not become widespread there until the 
middle of August. 
No records of the appearance of blight in the adjoining 
mainland counties of Dorset and Hampshire were received by the 
Food Production Department until the first week of August, hence 
it is probable that the blight fungus developed “ endemically ” in the 
Isle of Wight as regards Plots I and 2. 
Observations in the Penzance District. 
These were carried out by the writer alone and, on account of 
circumstances were of a more rapid nature than the observations 
madein the Isle of Wight. Nevertheless they are of interest. As is 
well known, early varieties of potatoes are grown on an extensive scale 
•n this part of Cornwall. The soil is particularly suitable for 
potato growing, being a light sandy loam of good quality, and 
