100 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
that the timing of the applications which give the most satisfactory con¬ 
trol of the root maggot parallels quite closely those which seem best 
adapted to prevent the development of Rhizoctonia. A very early 
application repeated once or twice at intervals of about a week seems to 
give the best results, while if these are deferred until later in the season 
the degree of control appears to be greatly lessened. 
Table 3 is comparable in every way to Table 2 except that instead of a 
simple aqueous solution of mercuric chloride a stock solution was first 
prepared by dissolving the salt in concentrated hydrochloric acid. 
It was found possible by this method to prepare a stock solution which, 
for convenience in the field, was graduated so that one fluid ounce con¬ 
tained exactly one ounce by weight of the bichloride. It seemed 
possible that in addition to the convenience of such a concentrated stock 
solution, the slight amount of acid present might increase the insecticidal 
or fungicidal efficiency or at least improve the stability of the dilute 
solution. This has not been very evident so far in the field tests, but it 
seems probable that under certain soil conditions the slight amount of 
acid present might increase the efficiency of the solution. It should be 
added here that in field tests the acid solution does prove appreciably 
more toxic to the plants under treatment than where no acid is used. 
While mercuric-chloride solutions seem to possess promise for the 
control of certain types of soil-infesting fungi, a word of caution may 
not be out of place. These solutions are not uniformly safe on all crops 
and under all soil conditions; for while some plants are quite tolerant to 
the treatment others may be seriously injured by heavy applications. 
Plants growing in extremely dry soils appear to be more liable to injury 
than where the soil is moist, and the reaction of a soil also has some 
bearing on the degree of safety. It is, therefore, not advisable to use the 
method indiscriminately until tests have been made to determine its 
safety for the crop which is to be treated. 
The bulk of the experiments so far carried out have been with the 
standard solutions containing 1 ounce of the bichloride to 10 gallons of 
water. Preliminary tests with much greater dilutions seem to indicate 
that these also possess marked fungicidal properties when applied to the 
soil, and if these greater dilutions prove equally efficient the danger of 
injury to tender crops would be correspondingly lessened. 
Just how wide an application this method will have, and what its 
relative value will prove to be in the control of different types of fungous 
diseases is by no means certain. It seems probable that its chief value 
will be for use against surface-infesting fungi or where it is merely a 
