July i, 1918 
True Nature of Spinach-Blight 
55 
SEED TRANSMISSION OF SPINACH-BTIGHT 
The occurrence of spinach-blight from time to time in commercial 
fields, and especially in new land which had never been planted to spinach 
before, suggested the possibility of seed transmission of this disease. 
During the period that the various experiments on the transmission of 
this disease have been conducted many thousands of spinach plants have 
been grown, some even to maturity in both greenhouse and field cages. 
In no case has there been any evidence that blight was transmitted 
through seed. When it is considered that the various seed strains used 
for this work have been obtained from practically all parts of the United 
States and Europe where spinach seed is grown, it would appear that the 
weight of data is against the idea of seed transmission of spinach-blight. 
During the spring of 1917 seed was collected from over a hundred 
blighted plants in various stages of the disease. Unfortunate circum¬ 
stances following the harvesting of this seed made it impossible to get 
immediately as many data as were desired relative to the transmission of 
spinach-blight by these seed; therefore this phase of the problem is not 
complete. The growing of spinach plants from the seed of these diseased 
plants is being conducted on a rather extensive scale, both in the field 
and in the greenhouse. 
POSSIBLE MEASURES OF CONTROL 
CONTROL OF INSECT CARRIERS OF THE INFECTIOUS ENTITY 
Probably the most effective and immediate control of spinach-blight 
can be obtained by destroying or otherwise eliminating the transmitters 
of the infectious entity of the disease. As aphids are usually the most 
abundant insects on spinach in this region during the time blight is 
present, efforts are being made at the present time to control them. 
During the winter parasites of the aphids are not as effective in holding 
them in check as they are during warmer periods. Also the predacious ene¬ 
mies of the aphids, particularly the ladybird beetles Hippodamia convergens 
Guerin and Megilla maculata De Geer, are hibernating and are of little 
benefit in reducing outbreaks of aphids between November 1 and April 1; 
hence, except for temperature conditions, natural control of aphids can not 
be counted upon to relieve the situation at this time. Experiments have 
been conducted for several years on spraying spinach for the control of 
aphids. It was noticed in 1914 and again in 1916 that on sprayed plots 
where the most effective control of aphids was obtained there was much 
less blight than on the unsprayed plots where the aphids were allowed 
to feed undisturbed. Not until the autumn of 1917 was an arrangement 
devised whereby spinach plants could be effectively sprayed to kill the 
plant lice. The present indications are that blight can be materially 
reduced by the timely application of sprays for the control of aphids. 
