-15- 
In 1937 Heal's work was referred to "by C. L. Smith ( 136 ) , who stated that 
the control obtained by Mr. Heal in these tests after two applications amounted 
to 99 percent. 
the 
Petherbridge and Thomas ( 121 ) In 1937 recommended the following spray lor / 
control of the fruit-tree red spider ( Paratetranychus piiosus_) : 
Mineral oil emulsion 
3-l/5 pints (85 percent oil 
by weight) 
Perris 
Water 
13 ounces 
1+0 imperial gallons 
Garman and Townsend (6U) in 193? reported that derris or cube sprays gave 
fair kills of the European red mite. These sprays do not affect the eggs and 
within a week are probably lost as killing agents for young, recently hatched 
mites. Some growers have reported successful control with derris or cube 
extracts combined with the regular sprays. Partial' success was observed at 
Lebanon in 1936 with powdered root, and somewhat better results were obtained 
at Cheshire a year or two previous, on prunes . When combined with the usual 
spray ingredients, rotenone extracts were not especially successful in the 
experiments of 1938. '^ e 1938 experience indicated that thorough applications 
of sujnmer oil alone give good clean-up without additional materials. 
Botenone extract 1:800, applied on July 25 to a single apple tree, per- 
mitted an increase in the number of adult females per 100 leaves from 1U3 
before spraying (July 19) to 180 on July 28 and 230 on August 3. Rotenone 
extract 1:800 applied at the same time to another apple tree caused the number 
of adult females per 100 leaves to range from llU on July 19 to 50 on July 28 
and 130 on August 3» A test was also made with rotenone extract 1.5:800 ^- dry 
lime-sulfur 3 pounds per 100 gallons + manganese sulfate l/U pound per 100 
gallons + lead arsenate 2 pounds per 100 gallons. Results were as follows: 
Time of examination 
Mites per 100 leaves 
Eggs i Adults 
July 28, before spray— 
August 2, after -spray — 
August 12, after spray- 
Number 
Number 
3,320 
980 
4,390 
190 
2,490 
680 
Perris powder (h percent rotenone) at U pounds per 100 gallons- killed 
90 percent of the European red mites present. 
Jary and Austin (_8l) in 1938 reported that during 1937 derris-petroleum 
-oil sprays gave a high degree of control of the fruit-tree red spider, which 
was otherwise xsry severe on plums. 
