- cJO - 
cooler coastal areas, these sprays ^ave satisfactory commercial results 
against i7rn0.tu.re llac'" scales, beir.3 onl ■ slightly less effective than the 
commercially used black scale oil sprays at ordinary dosages-. At slightly 
higher oil dosages, up to 1 or 1.25 percent, off-hatch scales were effec- 
tive! : ills ! i.n a ni ■ of orchards-. The particular advantage of these 
sfr black scale at that tine aas that they appeared to be 
sai r for use on nature Valencia fruit tr a: straight oil sprays, produced 
■ less oil effect cr the tree, and also checked aphids, if present. To 
date, derris sprays with 0,5 percent of light medium oil have shown litt! 
oil deposit, no interference with color, and ability to control the black 
scale s a t i s I a c t o r i ly „ 
The California Fruit Growers' Exchange, Bureau of Fest Control, 
(36, - . ■ . . , 46)j in August 1937 stated that in Ventura County, 
Calif,, b bed 3 ' lacl scale area in Bardsdale and Ciai 1 
be handled by ore of the d orris-oil sprays, with fewer adverse effects 
than the regular oil sprays. Also where it is impossible to fumigate 
overripe fruit without serious damage the derris-oil sprays might be used. 
The Lbzchs ige in February 1933 recommended cil-rotenone combinations for 
combat j e block scale associated v. r ith the red spider and the citrus 
aphid. A s\*i table spray is made from 0.5 to 0.75 gallon of light medium 
oil, 1 to 4 pounds of rotenone powder, and water to make ICO gallons. In 
July 1938 growers of oranges in Ventura County were advised that low- 
dor: rris-oil will handle the black scale and is easier en the trees 
ana Fr It, and in 1938 it was reported that oil-rotenone sprays had shown 
definite value not or] .7 in killing snail black scales but, in off-sea 
work, in destrc larger scales than did emulsions or emulsibles with 
the same amount of oil. The exchange stated. that in September 1939 light 
medium oil, medium oil, rotenone-oil sprays, and fumigation were methods 
largely used for control of S. oleae, according to the district; and in 
November 1939 the Exchange reported that oil-rotenone sprays at 0.75 to 
1,0 pe t of light medium oil are effective for mixed populations of 
the citricola and black scales. Oil-rotenone spray was more effective 
on advanced black scales than was raiscible oil and lime-sulfur and is 
less likely to retard coloration than straight oil, 
Mien used vrith oil, Tox-X is very effective against citrus black 
scale and is superior to oil alone, according to Leffingwell Company in 
a letter to P.. C. Roark in 1957. 
Boyce and Frendergast (19) in 1933 wrote that the oil-rotenone 
mixtures are relatively expensive -.hen considered for the control of red 
spider alone. However, when considered for the combined control of 
ads, red spider, and off-hatch black scale during the spring, they are 
very prac bical 
LaDue (17.9) in 1938 reported that pastes of derris with vari us 
.nic solvents added to oil sprays gave unsatisfactory results against 
£• <) ^ eae l on Washington ravel orange trees. Acetone and. ethyl ether- 
derris extracts wore also used, with low percentages of spray oil, but 
certain difficulties were encountered, such as the resins flocculating 
and going out of the oil phase into the aqueous phase. In "ohe early part 
of 1937 laboratory experiments were made using methyl isobutyl ketone, 
mcthyl-n-amyl ketone, and 2,2'-dichlorethyl ether as intermediary solvents 
^■■■■■■■^■■■■■MHii^HriMaHMU 
