THE PECAN LEAF CASE-BEAKER. 



21 



On Plats I and III the case-bearer was satisfactorily controlled, 

 while on Plat II, which was left untreated, very serious damage was 

 done during the spring by the overwintering larvae. Rather serious 

 injury was done to the foliage on Plats I and III, owing in part to 

 the showery weather that followed the spraying, which made con- 

 ditions favorable for the suspension of free arsenic on the leaves. 

 The sprayed trees shed their foliage a little sooner than the checks, 

 but defoliation did not take place so early as to cause the trees to 

 bud out again. 



A series of dosage tests with lead arsenate was carried out for the 

 purpose of determining the proper strength necessary to control 

 effectively the pest under orchard conditions. The results of this 

 work are contained in Table XVIII. 



% 

 Table XVIII. — Spraying experiments against the larvse of the pecan leaf case-bearer to 

 ■ determine the most effective dosage of lead arsenate; Monticello, Fla., 1914- 



Plat 

 No. 



Num- 

 ber of 

 trees. 



Treatment. 



Date of 

 appli- 

 cation. 



Results. 



Degree of 

 infestation. 



Arsenical injury 

 to foliage. 



I 

 II 



2G 

 16 

 31 

 6 

 37 

 24 

 21 

 18 

 26 

 24 



Powdered lead arsenate at 1 J pounds to 



50 gallons of water. 

 Powdered lead arsenate at 1 pound to 



50 gallons of water. 

 Powdered lead arsenate at h pound to 



50 gallon of water. 



1914 

 Aug. 20 



...do 



Practically none. 

 do 



Serious. 



III 

 IV 



...do 



...do 



Light infestation 



Very heavy in- 

 festation. 

 Light infestation 



Very light infes- 

 tation. 

 Practically none. 



do 



Slight burning. 



V 



VI 



VII 



VIII 



Paste lead arsenate at 1 pound to 50 gal- 

 lons of water. 

 Paste lead arsenate at 1£ pounds to 50 



gallons of water. 

 Paste lead arsenate at 2 pounds to 50 



gallons of water. 

 Paste lead arsenate at 2J pounds to 50 



gallons of water. .' > 

 Paste lead arsenate at 3 pounds to 50 



gallons of water. 

 Two pounds of paste arsenate of lead 



plus 4 pounds of lime to 50 gallons of 



water. 



...do , 

 Aug. 22 



...do 



...do 



...do 



Slight burning. 



Somewhat pro- 

 nounced. 

 Rather serious. 



IX 



do 



Do. 



X 



...do 



do 











burning. 



As is shown in Table XVIII, the powdered lead arsenate at | pound 

 (Plat III), and paste form at 1 pound (Plat V), as well as H pounds 

 (Plat VI) , to 50 gallons of water were found to be too weak for effec- 

 tive work, while the powdered lead arsenate at 1 pound and 1J pounds 

 and the paste form at 2, 2J, and 3 pounds gave very satisfactory 

 control. It was discovered that pecan foliage was quite susceptible 

 to arsenical injury, for on all plats there was some burning. The worst 

 burning occurred on Plats I, VIII, and IX, where the stronger dosages 

 of lead arsenate were used; but where the weaker dosages were 

 employed the injury was considerably lessened. The foliage on Plat 

 X, sprayed with lead arsenate to which lime was added, was in the 

 best condition, as only a trace of burning occurred. 



