26 BULLETIN 571, U. S. DEPARTMENT OF AGRICULTURE. 



could be relied upon to control the case-bearer. Paste lead arsenate 

 at 1 pound and 1^ pounds or the powdered form at J pound to 50 

 gallons of water did not give satisfactory results, but the case- 

 bearer was controlled equally as well with 1 pound of the powder or 

 2 pounds of paste as with 1£ pounds of the powder or 2 \ or 3 pounds 

 of the paste to each 50 gallons of water. ' 



In conducting extensive spraying experiments it was soon dis- 

 covered that pecan foliage is more or less susceptible to arsenical 

 burning. Experience showed that it was unsafe to spray pecan 

 trees with lead arsenate without adding at least 3 pounds of stone 

 lime to each 50 gallons of water. 



Fumigation experiments on the hibernating larvae on pecan twigs 

 and pecan nursery trees demonstrated that the larvae could be 

 destroyed by fumigating for one hour with 1^ ounces of sodium 

 cyanid per 100 cubic feet of space inclosed. 



RECOMMENDATIONS FOR CONTROL. 



Experimental work extending over a period of more than three 

 years has shown conclusively that no matter how badly an orchard 

 may be infested, the pecan leaf case-bearer can be controlled success- 

 fully by a single application of an arsenical solution combined with 

 lime, if made during the latter part of summer. Experiments have 

 shown that the best results are obtained by using 1 pound of the 

 powdered, or 2 pounds of the paste arsenate of lead and 3 pounds of 

 freshly slaked lime to each 50 gallons of water. Under no circum- 

 stances should arsenate of lead be used without the addition of lime, 

 as more or less injury to the foliage and nuts is likely to follow. It is 

 evident that spraying may be done with equal effectiveness at any 

 time between the first of August and the middle of September. 

 Spraying earlier than August 1 is not to be relied upon as being fully 

 effective, since all of the eggs will not have hatched by this time, 

 and during the course of the spraying it is considered advantageous 

 to the work to have all larvae feeding upon the foliage. There is 

 also some danger in delaying the spraying in the fall, as observa- 

 tions have shown that some larvae seek hibernation quarters toward 

 the latter part of September, although the majority of them do not 

 construct winter cases until the first week or so in October. It 

 should be borne in mind that only the larvae which feed on poisoned 

 foliage are killed, and those escaping pass the whiter in hibernacula 

 around the buds and come forth in the spring to feed upon the buds 

 and young leaves. Therefore, all who would combat successfully 

 the pecan leaf case-bearer must realize the importance of thorough 

 and timely spraying. 



