33 



The habits of young grasshoppers to seek the soil crevices during a 

 rain results in the burial of millions beyond the possibility of a resur- 

 rection. This, with the development and propagation of fungous 

 diseases among the nymphs, are the most potent natural agencies 

 which destroy grasshoppers during wet summers. 



The fact that the differential locust will deposit eggs in logs has 

 given some support to the idea that crevasse water introduces the 

 grasshoppers. There are sections of the delta, however, which are 

 almost annually overflowed by the high water of the Mississippi and 

 its bayous and which would be common infesting grounds were this 

 the case, but these do not seem to suffer except when dry summers 

 prevail. 



SOME INSECTICIDE EXPERIMENTS. 

 By C. L. Marlatt. 



A series of experiments with certain insecticide substances was made 

 in the spring and early summer of 1900 and are herewith recorded. 

 The experiments were especially designed to test the effect of various 

 substances which might be used against the San Jose scale, both as to 

 their effect on trees and efficiency as destroyers of the scale. They 

 included work with (1) crude petroleum; (2) refined kerosene; (3) lime, 

 sulphur, and salt wash; (4) hot water; (5) Bordeaux wash and kerosene 

 emulsion; and (6) a kerosene and lime emulsion. The experiments 

 with the latter two substances were made at the suggestion and with 

 mixtures furnished by Professor Galloway. An experiment was also 

 made, at the suggestion of Dr. L. O. Howard, with a heavy lime wash 

 or whitewash. For the washes containing lime the period immedi- 

 ately following the applications was unusually favorable, little rain 

 falling for upwards of two or three weeks. In the use of crude 

 petroleum and kerosene nothing especially new is to be noted except 

 the fact that the treated trees were not in any way injured and the 

 effect on the scale was all that could be desired. The lime and salt 

 wash, rather unexpectedly for the East, proved to be a very efficient 

 insecticide, doubtless owing to the fact, however, that the weather 

 conditions were exceptionally favorable. The lime emulsion indicated 

 good results. The Bordeaux and oil mixture was less favorable, and 

 the whitewash spray, while most promising in appearance at the out- 

 set, was valueless as to results in the outcome. 



Crude and refined petroleum,. — A series of plum, apple, and pear 

 trees were sprayed March 22 with crude petroleum (43° Baume), the 

 applications being made thoroughly enough to completely wet the bark. 

 The plum trees were thickly infested with Diaspis pentagona and the 

 pear trees with the San Jose scale. Some of these trees had been 

 pruned back heavily, and others were straggling trees 10 or 12 feet in 



4670— No. 30—01 3 



