July i, 1918 
True Nature of Spinach-Blight 
57 
(3) Spinach-blight is distinguished from fungus diseases by the fact 
that there is no specific microscopic organism associated, and that the 
various fungi produce definite leafspots, while spinach-blight causes a 
gradual degeneration of the tissues. 
(4) Opinions vary as to the time when spinach-blight first ap¬ 
peared in eastern Virginia. One grower reports it as serious at least 
13 years ago. 
(5) Mr. L. E. Harter, of the United States Department of Agriculture, 
worked on malnutrition diseases of various truck crops, and it is evident 
from his published reports that spinach-blight was included among 
these diseases. The early work on these diseases resulted in the use of 
better cultural methods. 
(6) This blight has increased in seriousness from year to year. During 
the past 10 years the disease has spread until it is now present annually 
throughout eastern Virginia wherever spinach is grown commercially. 
(7) For some years past it has been observed that spinach-blight 
became most serious within a short time after aphids were observed to 
be abundant on the plants. These observations led growers to suspect 
that the aphids were the direct cause of this disease. 
(8) Some spinach growers were of the opinion that spinach-blight was 
due to poor soil drainage. Data relative to this point proved that the 
drainage within blighted areas was usually as good and often better than 
that in other parts of the field where the plants were healthy. 
(9) Fertilizer experiments conducted in 1915 and 1916 proved that 
stable manure, lime, and commercial fertilizers applied to land where spin¬ 
ach-blight had been very serious the year previous had no direct influence 
on the development of the disease. Experiments with the substitution 
of fertilizer elements not commonly used, for those generally employed 
in making up commercial fertilizers had no effect in reducing the amount 
of blight. 
(10) By a repetition of earlier work in an attempt to determine whether 
or not fungi or bacteria were associated with blighted plants, it was 
found that tissues of plants in early stages of the disease remained 
sterile on plates of nutrient media. Plants in more advanced stages of 
spinach-blight, where the tissues were breaking down, yielded numerous 
fungi and bacteria. When healthy spinach plants were inoculated with 
pure cultures of each of these organisms, no blight was produced. 
(n) Inoculations made in the winter of 1915-16 with the juice of 
blighted spinach plants gave indications that the disease was of an 
infectious nature. 
(12) In eastern Virginia spinach is grown in the fall, winter, and early 
spring. During this period two species of Aphididae, the potato aphis 
(Macrosiphum solamfolii Ashmead) and the spinach aphis (.Rhopalo - 
siphum persicae Sulzer) are the most abundant insects on spinach. 
Several other species of insects are found associated with spinach during 
