OBSCUKE SCALE ON THE PECAN AND ITS CONTROL 



13 



Table 3. — Average effectiveness of all oil dilutions used, as indicated by data in 

 table 2, in spraying experiments on the obscure scale on pecan trees, Shreveport, 

 La., 1932. 



Percentage of oil 



in spray 



Tests 



Average 



■degree of 



control 



Percentage of oil in spray 



Tests 



Average 

 degree of 

 control 



4 



Number 

 8 

 8 



Percent 

 66.8 

 86.2 



6 



Number 

 8 

 3 



Percent 

 94.2 



5 



8 



96.8 









Table 4. — Effect of oil sprays on dormant pecan trees, Shreveport, La., 1932 





Dilu- 

 tion 

 used 



Effect of oils on trees to which applied 





Bottom-land orchards 



Hill-land orchards 



Oil 

 no. 



Planted in alfalfa, 

 soil fertile, twig 

 growth moderate, 

 foliage good until 

 affected by 

 drought late in 

 fall 1931; trees as 

 a whole moder- 

 ately vigorous. 

 Sprayed Feb. 29 



Tree rows clean 

 cultivated, soil 

 fertilized, twig 

 growth strong, 

 foliage excellent; 

 trees unusually 

 vigorous. Sprayed 

 Mar. 2 



Cropped with 

 cotton, soil poor, 

 twig growth light 

 to moderate, fo- 

 liage fair until 



affected by 

 drought early in 

 fall of 1931; trees 

 fairly vigorous. 

 Sprayed Feb. 12 



Clean cultivation in summer, 

 winter cover crop planted but 

 died out, soil poor, eroded, twig 

 growth light, foliage poor; trees 

 lacking in vigor. Sprayed Feb. 

 24 



17 



Percent 



4 

 5 

 6 

 4 

 5 

 6 

 4 

 5 

 6 



8 



12 



4 

 5 

 6 



8 

 12 



4 

 5 

 6 

 4 

 5 

 6 



8 

 12 

 4 



5 

 6 

 8 

 12 













do 



do 











None 





14 



- do . 





-. do . 







do 



do 



do 





-.--do... . 







do 





16 



do 



Light, twig tips injured. 





Trace 





do- 







do 





Light, 2 small 

 limbs serious- 

 ly injured. 











limbs killed. 











killed. 

 Severe, 50-60 percent limbs 



killed 

 Light, 3-4 small limbs hurt. 



I s ) 











do. . 





do 





Trace .. 

















limbs killed. 

 About same as 6 percent dilution. 

 Severe, about 70 percent limbs 



injured. 











6 



None. 



None 



None .- 





Trace . ... . 



do . . 



.- do 







None .---- 



do 







18 



do.„ 







Trace, a few twig tips hurt. 





do 





do 





Light, 2-3 small 

 limbs killed. 





Moderate, con- 

 siderable weak 

 sickly foliage. 



Light, 2-3 small limbs made weak 

 growth. 



Light, retarded bud opening, 1 

 medium sized limb killed. 



Severe, 50-60 percent of tree seri- 

 ously injured. 



Light, twig tips injured, 1 small 

 limb made poor growth. 



Moderate, some dead twig tips, 

 4-5 small limbs killed. 



Severe, 20 percent of tree seriously 

 injured. 



Severe, 50-60 percent of tree seri- 

 ously injured. 















IP 











do 



Trace 





do- 



do 



























The data in tables 2 and 3 indicate that it is an extremely difficult 

 task to obtain a 100 percent kill of the obscure scale, three tests in 

 which 8 percent lubricating-oil emulsions were used failing to give 

 such a kill. At the same time, these and other tests (table 4) showed 

 this strength of oil unsafe for application to dormant pecan trees. 

 The data furnish, to a large degree, the answer to the problem as to 



