398 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



experiment, 95% in the second, and 95.2% in the third. The niunber of 

 n>Tnphs counted in the three experiments was 46, 106, and 681 respective- 

 ly. The foregoing tests were somewhat less dependable in the case of 

 the adults since some of those which did not drop from the first application 

 may have left the plants. In one test however in which a square block 

 of 16 vines was dusted, a second thorough dusting 24 hours after the first 

 showed that about 55% of the adults had been killed or had disappeared 

 from the central block of four vines. Nine hundred and sevent^^-four 

 adults were included in this count. Only those which dropped from each 

 vine into a bucket within five minutes after the dust was applied were 

 included, the estimated total for the average plant being about 1700. 



Observations ox the Use of Nicotine Dusts Against the 



Melon Aphis 



Investigations of the writer in the Imperial valley and other points in 

 Southern California have not developed m.uch of practical value to add to 

 the discussion of melon aphis control presented by Mr. Roy Campbell 

 in Circular 154 of the U. S. Dept. of Agriculture. For scattering infes- 

 tations the writer advises nicotine dusts with not less than 2.4% nicotine. 

 This requires about 7>^% of Blackleaf 40 in manufacture. The expense 

 in this case is partly for insurance of the uninfested plants against the 

 spread of the insects. When the infestation is general throughout the 

 field and the problem has become one of reasonable control for the 

 purpose of maturing a m.arketable crop, with no consideration for restric- 

 tion of spread, adust with about 1.5% of nicotine, or 4 or 5% Blackleaf 

 40 used in manufacture, is to be preferred. 



The need of early season scouting or patrolling of the melon fields to 

 locate incipient aphis colonies cannot be too strongly emphasized. 

 Paradoxical as it may seem., the most expensive treatment on a basis of 

 cost per hill is the most economical. Growers can better afford to spend 

 $4.00 a day for patrolling in early season when a man can find only one 

 or two infested plants each day, at a cost of two to four dollars per hill 

 for labor alone, than he can afford 5c a hill for both labor and material in 

 dealing with a general infestation when the melons are beginning to 

 mature. If a commercial melon field were so generally infested through- 

 out as to require treatment of all the vines with an insecticide to save the 

 crop, the cost of dusting would be prohibitive. Such a condition seldom 

 if ever occurs however, since ordinarily by the time such a widespread 

 infestation has developed a large percentage of the plants are already 

 dead. 



