12 



CIRCULAR 295, U.S. DEPARTMENT OF AGRICULTURE 



difference in the degree of injury caused by the three oils that were 

 used, each oil causing about the same injury at the 6-percent dilution. 

 A few of the trees sprayed with the lubricating oils at the 4-percent 

 dilution showed a few injured twigs (as evidenced by delayed bud 

 opening), but in no case was the injury extensive or serious. Except 

 from the 6-percent oil dilution in the December application, none of 

 the injury was as much as would result from permitting a moderate 

 or heavier infestation of the obscure scale to develop unimpeded. 

 As the only reaUy serious injury occurred as a result of the early 

 December application, it was attributed to the fact that the trees 

 had not become fully dormant, with the added possibility that the 

 condition of the trees may have been partially responsible owing to 

 the fact that they had suffered considerably from drought during 

 the preceding summer and early fall with subsequent premature 

 defoliation. The liquid lime-sulphur and the miscible oils caused 

 no injury in the tests in which they were used. 



Experiments were carried out during the dormant season of 1931-32 

 for the purpose of obtaining further information concerning the effect 

 of oils of different physical characteristics on pecan trees and their 

 effectiveness in controlling the obscure scale. The tests were applied 

 with a power sprayer in a number of orchards offering varied con- 

 ditions; some of the orchards were planted in bottom land, some 

 in hill soil, some were intercropped, some were maintained in clean 

 cultivation, some were healthy and vigorous, while others were 

 growing under unfavorable conditions. Data snowing the effective- 

 ness of the materials used in these tests are given in tables 2 and 3, 

 and data indicating their effect on the trees are given in table 4. 



Table 2. — Results of spraying experiments on the obscure scale on pecan trees. 



Shreveport, La., 1932 



[Approximately 1,000 scales were examined in each test except in check test no. 25, in which 2,000 were 

 examined. Tests nos. 1-25, inclusive, were in one orchard and tests nos. 26-29, inclusive, were in a second 

 orchard] 



Test 

 no. 



Material used 



Dilu- 

 tion 1 



Scales 

 dead 



Con- 

 trol 

 ob- 

 tained 



Test 

 no. 



Material used 



Dilu- 

 tion i 



Scales 

 dead 



Con- 

 trol 

 ob- 

 tained 



1 



Oil 17 2 3 



Per- 

 cent 

 4 

 5 

 6 

 8 

 4 

 5 

 6 

 4 

 5 

 6 

 8 

 4 

 5 

 6 

 4 



Per- 

 cent 

 77.05 

 97.36 

 98.54 

 95.87 

 83.67 

 85.70 

 96.37 

 86.25 

 97.78 

 97.90 

 98.64 

 75.13 

 92.42 

 98.53 

 63.97 



Per- 

 cent 

 68.7 

 96.4 

 98.0 

 94.4 

 77.7 

 80.5 

 95.0 

 81.2 

 97.0 

 97.1 

 98.1 

 66.0 

 89.6 

 98.0 

 50.8 



16-... 



17 



18..- 

 19.— 



Oil 6 



Per- 

 cent 

 5 

 6 

 4 

 5 

 6 

 4 

 5 

 6 

 8 



Per- 

 cent 

 90.10 

 92.70 

 81.32 

 87.04 

 97.83 

 5S. 10 

 83.10 

 91.70 

 98.46 

 26.75 

 80.21 

 85.81 

 92.47 

 27.97 



Per- 

 cent 

 86.5 



2 



3 



do 



do 



_ do 



do 



Oil 18 



90.0 

 74.5 



4 



do 



82.3 



5 



Oil 14 .. 



20.— 

 21.... 

 22 ... 



do 



Oil 19 



97.0 



6 



do 



42.8 



7 



do .. 



.... do 



76.9 



8 



Oil 16 



23—. 

 24— 



do 



. do— 



88.7 



9 



do - 



97.9 



10 



do 



do 



Oil 15 



25— 

 26.— 

 27— 

 28 .. 



L nspraved check. .. 





11 



Oil 6 



4 

 5 

 6 



72.5 



12 .. 



do 



.... do 



80.3 



13 



. do 



89.5 



14 



do 



29.... 







15 



Oil 6 .. 















1 Percentage oil in the dilute emulsion. 



2 For characteristics of oils used, see table 6, p. 18. 



3 All oils emulsified according to formula no. 2, p. 17. 



