9 



EXPERIMENTS CONDUCTED BY THE U. S. DEPARTMENT OF 



ACtRICTJLTTJRE. 



TREATMENT OF SMALL AHEAS, WITH CAREFUL EXAMINATIONS. 



Conditions covered and methods employed. — In the following series of 

 tests, in order that the number of weevils killed by the poison might 

 be accurately determined, the plants to l>e treated were carefully 

 examined to lind the number of weevils . present, disturbing them as 

 little as possible. A tag bearing all necessary information regarding 

 the conditions of the test and of the weevils was placed with each 

 plant. Papers were then spread under the plants, extending con- 

 siderably bej^ond the spread of the branches to catch the dead weevils. 

 In spite of this precaution it was soon found that a large proportion 

 of the weevils were missing when later examinations were made. As 

 soon as this fact was observed weevils, so marked with colored pencils 

 as to be positively identifiable, were used, the weevils so marked con- 

 stituting over 76 per cent of the total number treated. The tests were 

 conducted from April 19 to May 19, giving a range of weather condi- 

 tions. These were varied by making applications on calm and on 

 windy days, some early in the morning while the plants were wet with 

 dew, others during the middle of the day when the plants were drj'^, 

 some in the middle of the day but spra3dng the plants to give dew 

 conditions. Plants with and without squares were treated, and in 

 three of the tests plants used in the test immediately preceding were 

 re-treated, together with the weevils surviving the previous test, thus 

 making conditions as severe as was possible. In part of the tests the 

 poison was applied with a powder gun, and in the remainder was 

 used the method employed for many years in using Paris green against 

 the cotton-leaf worm — of shaking the poison from a sack. An exceed- 

 ingly heavy rate was used, since the object of the tests was to kill the 

 weevil if it were possible to do so with Paris green. 



Spraying, — On April 27 a test was made with a spray consisting of 

 1 pound of Paris green in 30 gallons of water, 49 plants with 94 wee- 

 vils on them being thoroughly sprayed. At the last examination, 

 made 72 hours after the application, 78 weevils were found alive, 5 

 dead, 11 missing; 82.97 per cent surviving. Since this test was not 

 as successful as the tests with dry Paris green nothing further was 

 done with the spray. On this point Prof. E. D. Sanderson (Farm and 

 Ranch, October S, 1901:, p. 16) says: 



The dry dust also seems to kill the weevil? somewhat more quickly, though in the 

 liquid form the poisons are just as fatal. 



Poison blown by a powder gun. — The plants were dry when treated 

 in three of these tests, and the powder was blown in from all direc- 

 tions. Four tests (Table I, Nos. 1, 2, 3, 5) were conducted on seppa 



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