50 



BULLETIN 746, U. S. DEPARTMENT OF AGRICULTURE. 



On a plantation scale, however, such a treatment, even in a modi- 

 fied form, would be impossible. Experiments have shown that treat- 

 ment of cane cuttings on a plantation already infested with the moth 

 borer and the mealybug has little or no effect in reducing the sub- 

 sequent infestation. In the season of 1911-12, a very great effort was 

 made to eliminate sugar-cane insects from a small property in Loui- 

 siana. The trash on the fields was burned in the fall, the entire farm 

 was given over to plant cane, no cane was windrowed, all cane was 

 planted in the fall after having been dipped in a fish-oil soap solu- 

 tion (to kill the mealybugs), nearly all the stubble was removed from 

 the fields (according to the plans all the stubble was to be removed, 

 but the work was so difficult and expensive that some of the stubble 

 was plowed under to a depth of 4 or 5 inches), and, finally, the plant- 

 ing of corn was delayed in the spring of 1912 so that any possible 

 hibernated moths of the borer would not find corn as an early food 

 plant. While the work may not have been done in an absolutely 

 ideal way, the experiment was much more thorough than ordinarily 

 would have been possible. 



Even the weather seemed to cooperate to render the experiment a 

 success. The winter of 1911-12 was cold, and the cane was late in 

 sprouting in the spring, so that it seemed that there was no cane dur- 

 ing the winter to serve as a food plant for the borers. Small borers 

 were found, however, as early as May 24, 1912, and by October 17 

 the infestation ran as high as 75 per cent, with an average of 59 per 

 cent. As to the mealybug, practically all the plants were infested. 

 The experiment was evidently entirely negative in its results. 



More exact experiments have been conducted to indicate the actual 

 effect of fumigation and immersion on both the insects and the sugar- 

 cane cuttings. Table VIII gives the results of dipping cuttings in 

 various insecticides and fungicides and also of soaking the cuttings 

 in the solutions for one hour, the borers afterwards being cut out to 

 ascertain whether they were yet alive. The borers were kept and fed 

 for about two weeks after the treatments. 



Table VIII. — Effect on moth-borer larvce of immersion of infested cane cuttings. 



Solution. 



Expo- 

 sure. 



Num- 

 ber of 

 lar- 

 vse. 



Condition of larvre im- 

 mediately after treat- 

 ment. 



Penetration of solution 

 in cane cutting. 



Condition 

 of larvae 

 two weeks 

 after treat- 

 ment. 





Dip... 



lhour. 



Dip... 

 1 hour. 



9 



6 



9 

 11 





Penetrated, and was 



deposited, on sides of 



holes. 

 Some of the stalks were 



evidently full of the 



solution. 

 Evidently penetrated 



the stalks. 

 do 







do 



All dead. 



Fish -oil soap, I pound 

 pur gallon water. 



do 





All alive, 4 had emerged 

 from cane atid were in 

 the solution. 











