IO 
Journal of Agricultural Research 
Vol. XIV, No. i 
in a few instances where the plants used were very young it was neces¬ 
sary to make the inoculations in the cotyledon leaves. 
It was noticed in making the transfers of aphids to young spinach 
plants that they generally fed on the under side of the leaves rather than 
on the stems or petioles; hence, it is probable that in the majority of 
cases the inoculations were made from that point, when virus-bearing 
aphids were transferred to healthy spinach plants. 
In making transfers or in any way handling the experimental plants 
the greatest care was exercised to keep the hands and instruments disin¬ 
fected. Ninety-five per cent alcohol was used for this purpose. Great 
care was also exercised when making transfers of insects from diseased 
to healthy plants. The insects were carefully removed from a diseased 
plant by means of a camel’s-hair brush, and were then placed on sterile 
glass slides on which they were carried to the healthy plants. They 
were removed from the slide by jarring it slightly. In this way neither 
instrument nor hand came in contact with the healthy plant Needles 
and other instruments used in making prick inoculations were carefully 
flamed between each operation. In the field cages certain soil-inhabiting 
insects would occasionally gain access to the spinach plants and often¬ 
times attack them. This was almost entirely eliminated by thoroughly 
drenching the soil in the cage with a i to ioo solution of 40 per cent 
nicotine sulphate at the time it was set in the field. 
In the majority of cases the precaution was taken to disinfect the 
spinach seed in 1 to 100 formaldehyde for a few minutes prior to planting. 
The majority of plants used in the greenhouse were grown from seed 
planted in steamed soil. 
INSECTS COMMONLY ASSOCIATED WITH SPINACH AT THE TIME BLIGHT 
IS PREVALENT 
Two species of Aphididae are primarily associated with spinach at the 
time blight is prevalent. These are the potato aphis (. Macrosiphum 
solanifolii Ashmead) and the spinach aphis (Rhopalosiphum persicae 
Sulzer). Blight occurs most abundantly between the 1st of November 
and the 1st of April, and these aphids are prevalent at all times during 
the winter months. As will be shown, several other species of insects 
are capable of transmitting spinach-blight from diseased to healthy 
plants, but they are of minor importance in this connection. Thus far, 
these two species of aphids have been found to occur in Tidewater, Va., 
only as viviparous females. The true sexes have neither been collected 
nor reared. From our studies of the species it has been found that M. 
solanifolii is more active and reproduces more readily during periods of 
low temperature than R. persicae. Laboratory studies relative to these 
facts have been confirmed by field observations. The feeding habits of 
the two species are somewhat different. M. solanifolii are ungregarious, 
the alate and apterous forms move readily from plant to plant during 
