2 
Journal of Agricultural Research 
Vd. XIV, No. i 
more prevalent. It is not unlikely that spinach-blight is present in 
other States where this crop is grown either for truck or seed purposes. 
The majority of the experiments recorded in this paper have been per¬ 
formed during the past three years, and the direct inoculation experi¬ 
ments, under the controlled conditions of field and greenhouse cages, 
have been conducted since the fall of 1916. As the problem is far from 
complete and many important points are as yet unsettled this paper has 
been prepared as a preliminary report dealing with the nature of the 
disease, its dissemination, and transmission by insects. 
In this cooperative undertaking certain of the generalized points 
herein presented have been proved by each worker independently, and 
the results then compared. The experiments relative to the insect trans¬ 
mission of the disease, together with the determination of the conditions 
by which this is influenced and controlled, were performed by the ento¬ 
mologist. The experiments on the relationship of soil, fertilizer, and seed 
conditions to spinach-blight, and the various virus inoculations to deter¬ 
mine the points relative to the nature of the disease were performed by 
the plant pathologist. 
DESCRIPTION OF SPINACH-BLIGHT 
Spinach-blight is a specific disease characterized by mottling and mal¬ 
formation of the leaves (PI. A). Although having many of the symp¬ 
toms of the mosaic diseases of tobacco, cucumber, etc., spinach-blight 
differs from them in that the affected plants are eventually killed. 
(PI. 1, A.) The disease appears either on plants scattered over the field 
(PI. 1, B) or on many adjacent plants, thus forming a distinct area. 
This blight may be distinguished from the various fungus diseases 
with which it may be associated, such as downy-mildew, caused by 
Peronospora effusa (Grev.) Rbh. (PI. 2, A), Heterosporium leafspot, 
caused by Heterosporium varidbile Cke. (PI. 2, B), and anthracnose, 
caused by Colletotrichum spinaciae Ell. and Halst. (PI. 3, A), because 
no microscopic organism is found associated with it. Spinach-blight 
may also be distinguished from diseases produced by the above-named 
fungi, by its causing a gradual degeneration of the tissues instead of 
definite leafspots. It has been observed that blighted plants are more 
susceptible to the attacks of certain fungi than are adjoining healthy 
plants. That the blighted plants are lower in vitality is shown by the 
fact that such plants are most seriously injured by occasional cold periods 
during the winter (PI. 3, B). 
Owing to the appearances of the blighted plants at various periods in 
the course of the disease, it is difficult to give a description which would 
be inclusive of their appearance at all times. For convenience eight 
purely arbitrary stages have been selected, as they offer rather marked 
