44 BULLETIN 100, U. S. DEPARTMENT OP AGRICULTURE. 



shoots were opened. A general survey of the sprayed block and of a check unsprayed 

 block indicated equal infestation by young stem mothers. Plant lice were not all 

 hatched. An examination made April 15, 1913, showed that trees were well out in 

 leaf. All stem mothers had hatched. A general survey of sprayed and unsprayed 

 trees showed no apparent difference in infestation. A count of 28 leaf clusters selected 

 at random from the sprayed trees yielded 21 stem mothers, while a similar count of 

 the same number of leaf clusters from unsprayed trees yielded 29 stem mothers. It 

 may be inferred from this experiment that the crude-oil emulsion destroyed few, if 

 any, of the winter eggs. 



Experiment No. 2. — Commercial lime-sulphur, 1-10. (Concentrated solution, 33° 

 Baume\) Orchard of Mr. George Whitman, Concord, Cal. A block of four large trees 

 of the European walnut were sprayed March 5, 1913, under a pressure of 100 pounds. 

 About 14 gallons of spray were applied to each tree and " Friend" angle nozzles used. 

 Eggs were abundant on both sprayed and check trees. The leaf buds on these trees 

 began to open April 1, 1913. Examination was made April 15, 1913. Trees were then 

 well out in leaf. The stem mothers were all hatched. The lime had no effect in 

 retarding leafing. A count of 20 leaf clusters taken at random on the sprayed block 

 yielded no plant lice, while a similar count of the same number of leaves on the check 

 trees yielded 27 stem mothers. Further examination showed that on the sprayed 

 trees no plant lice could be found, while on the check trees nearly every leaf cluster 

 had one or more of the insects. 



A subsidiary experiment was undertaken on two young California black walnut 

 trees, both infested with eggs. One of these trees was treated with commercial lime- 

 sulphur, 1-9 (concentrated solution 33° Baume), and the other left as a check. On 

 the sprayed tree no eggs hatched and when examined on April 17, 1913, the eggs were 

 shrunken and distorted, the embryos having been destroyed within the eggshell. 

 The eggs on the check tree hatched normally about the end of March. 



Experiment No. 3. — Crude-oil emulsion, lime-sulphur, and u Yel- 

 ros." Vrooman orchard, Santa Rosa, Cal. Four plats were 

 sprayed, April 9-11, 1913, with a power outfit at high pressure, as 

 follows: Plat 1, 40 trees, crude oil (22° Baume) emulsion, 8 per cent; 

 plat 2, 40 trees, lime-sulphur, 1 to 8; plat 3, "Yel-ros," 1 to 25, 

 16 trees; plat 4, "Yel-ros," 1 to 40, 24 trees. These applications 

 were made on late Franquette walnuts, dormant at the time of spray- 

 ing. The orchard was well infested with the winter eggs of the plant 

 lice. An examination, May 27, 1913, showed that the trees were well 

 out in leaf. Stem mother plant lice were mostly about two- thirds 

 grown. Counts of 80 leaves (about 480 leaflets) taken at random 

 from each of the four plats and from a check unsprayed plat resulted 

 as follows : 



Table XV. — Winter spraying experiment No. 3 against walnut aphides, Vrooman 

 orchard, Santa Rosa, Cal., 1913. 



Plat. 



Crude-oil emulsion, 8 per cent. 



Lime-sulphur, 1 to 8 



"Yel-ros," 1 to 25 



" Yel-ros," 1 to 40 



Check —unsprayed 



Number of 

 "lice" on 

 80 leaves. 



11 



2 



14 



97 



104 



Per cent 

 of number 

 on check. 



10.6 



1.9 



13.4 



93.2 



100.0 



