February, ’24] 
frost: red spider control 
103 
doubt they will develop in numbers sufficient to be injurious. As the 
delayed dormant application is used quite universally throughout 
Southern Pennsylvania, the possibilities of control measures here are 
encouraging. 
Summer Applications of Spray and Dust 
Summer applications of various forms of sulphur sprays have proved 
very satisfactory in keeping this pest in control. The sprays must be 
continued throughout the summer. The complete spray schedule for 
apple is usually sufficient to keep the red-spider in check. Sulphur and 
lime dusts, on the other hand, have given little or no control. As 
a matter of fact the most serious outbreaks of red-spiders have been 
found in neglected orchards or in dusted orchards. This together with 
other reasons have led the writer to believe that the water as well as the 
pressure have much to do with the control of red-spider. 
The writer has found it difficult to obtain figures to illustrate control 
work during the summer. The following tables are presented which 
are summaries of field notes for a period of four years indicating the 
nature of the control effected. In these orchards from five to six 
applications were made throughout the summer. The treated plats were 
adjacent to each other in the same orchard. The value of sulphur was 
tried chiefly in the liquid and the dust form. The cost of nicotine 
throughout the summer prohibited its use. 
Control of the Red-spider (Paratrtranychus pilosus C. & F.) 
Spray Applications Dust Applications 
Material 
Nature of 
Number Numbtr 
Material 
Nature of Number Number 
Control 
of years 
orchards 
Control years 
of orchards 
B. T. S.... 
good 
1 
1 
Sul. lead 
little or no. 
. r 
Atom. S. . . 
good 
1 
2 
90-10. 
4 
3 
Sol. S. 
good 
2 
1 
Sulphur 
some on 
Dry Mix.. . 
fair 
1 
4 
hot days 1 
2 
L. Sul. 
good 
4 
3 
Sul. lime 
little or no. 
50-50. 
1 
1 
Sul. lead 
little or no. 
Nic. 90- 
10, 2% 
2 
2 
Lime 
somt when 
used heavy 1 1 
Mr. T. J. Headlee : Did you say you used lime sulphur only in killing 
the eggs ? 
Mr. S. W. Frost: We used lime sulphur for killing the eggs but 
applied the regular schedule for aphis and for red spider. 
