14 
THE COLORADO EXPERIMENT STATION 
• indicated the results. The first was that shown in a count made April 
25, of living and dead insects upon the bark; and the second, of more 
practical interest, a comparison shown by a count on August 17, at 
the time of the last harvest, of the number of pears showing pits upon 
their surfaces. 
COMMERCIAL REX MIXTURE. 
Rex is a concentrated lime and sulphur mixture prepared by 
boiling together the two ingredients until combined and removing 
for use only the clear, reddish liquid free from sediment. It is a 
product prepared and sold by Rex Stock Food Co., of Omaha, Neb. 
It has been formerly used as a stock dip in the West. For spraying, 
it has only to be diluted with cold water. Lime may be added if 
desired. The lime is added so that a white coating may be left upon 
the tree indicating where parts have been completely covered, and to 
hold the spray temporarily upon the surface, causing more of the mix¬ 
ture to dry and adhere than would do so if applied as a clear liquid. 
Referring to the preceding table, it will be seen that both strengths 
were effective in reducing the number of scales upon the trees so that 
injury to the fruit was prevented. The slight difference in their effec¬ 
tiveness may be practically overlooked when these two results are 
compare with the 96.1 per cent of fruit rendered unfit for market 
upon the unsprayed trees. Some of the infested pears, unsprayed, 
bore at picking time no less than 328 attached scales of varying sizes. 
The scales dead upon the tree on April 25, twenty days after 
spraying, was 85.2 per cent upon the Rex of stronger dilution, and 74.9 
per cent dead upon trees sprayed with the weaker mixture. The 
action of all lime-sulphur sprays is continued for a considerable time 
after spraying. The former figure represents the increased effectiveness 
produced by an increase in strength and the addition of milk of lime. 
Both may be classed as of value in comparison with the 48 per cent 
dead upon the check. It will be remembered 31 per cent of the scales 
indicated by count were dead at the beginning of the experiment and 
the per cent scales dead as counted upon April 25 on sprayed plats 
included the 31 per cent shown to be dead from natural causes without 
treatment. The per cents given, therefore, under estimate the ratio 
of benefit actually derived from the sprays. 
In summing up it may be said that Rex lime-sulphur diluted one to 
eight with cold water with lime added as per formula is an effective 
spray against the Howard scale. It is not recommended as more 
effective than the standard orchard-boiled lime and sulphur washes. 
As was shown by experiment, the latter were slightly more effective 
than the Rex even when used at the stronger strength, but the ease 
and convenience of preparation of the Rex recommends it to the use 
of orchardists not fitted with the appliances for boiling their own spray. 
Some growers prefer to pay more for material and save the time and 
labor of preparing their own mixture. Examination of the scales shows 
them more loosely attached to the bark than is the San Jose scale, 
thus affording less resistance to the spray in coming in contact with 
the body of the insect. 
