THE PECAN LEAF CASE-BE AKER„ 25 



sulphuric acid, and 2 fluid ounces of water should be used to each 

 100 cubic feet of space inclosed. In purchasing sodium cyanid 

 it is essential to obtain a high-grade product, 96 to 98 per cent pure, 

 or, in other words, one that contains not less than 51 per cent of 

 cyanogen. Commercial sulphuric acid, specific gravity 1.84 (66° 

 Baume), which is approximately 93 per cent pure, should be used 

 for fumigation in order to obtain the best results. 



SUMMARY. 



Although the pecan leaf case-bearer is preyed upon by a number 

 of parasitic insects and several species of birds, it was found during 

 a course of studies extending over a period of three years that 

 neither the parasites nor any other natural checks could be relied 

 upon to control it, but that certain artificial measures were suc- 

 cessful. 



It was found impossible successfully to control the pecan leaf 

 case-bearer during the dormant season, at which time the larvae 

 were in hibernacula around the buds. Of the various spray materials 

 tried for the destruction of hibernating larvae, commercial lime- 

 sulphur solution at the strength of 1 : 8 and 1 : 10 gave the best 

 results, but this method failed to destroy a sufficient number of 

 the larvae to justify its use. Tests with miscible oils at 1 : 12, 

 1 : 15, 1 : 18, and 1 : 20, and 10 and 20 per cent kerosene emul- 

 sions applied during the dormant season were found to be ineffective. 



Because of the manner in which the larvae feed upon the buds 

 and foliage, the pecan leaf case-bearer in the active larva stage 

 during the spring was not satisfactorily controlled. Spraying ex- 

 periments, using a single application of arsenate of lead (paste) at 

 3 pounds to 50 gallons of water, 40 per cent nicotine sulphate at 

 1 : 700, and commercial lime-sulphur solution at 1 : 40, were tried 

 on orchard pecan trees as the larvae emerged from their hibernacula, 

 at which time the buds were beginning to unfold, but none of these 

 materials proved effective. Two applications of arsenate of lead 

 (paste) at 3 pounds to 50 gallons of water were made on large pecan 

 trees, the first as the larvae emerged from their winter cases and the 

 second eight days later. This treatment destroyed many larvae but 

 was not entirely effective. 



Experiments in spraying with certain strengths of lead arsenate, 

 conducted during the summer (August), gave very satisfactory 

 results in the control of this pest, as it was discovered that the 

 young larvae might be destroyed readily at this stage. Based on a 

 large series of dosage tests with lead arsenate, conducted on orchard 

 pecan trees, it was found that no strength weaker than 1 pound of 

 the powdered form or 2 pounds of the paste to 50 gallons of water 



