68 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
Weeds growing in borders, terraces, etc., and dooryard plants (in 
the case of fields near dwellings) constitute the sources from which 
red spiders are able to enter cotton fields. The invasion of fields is 
accomplished either (1) by travel upon the ground, (2) by travel from 
leaf to leaf, (8) by the wind, (4) by rain and surface water, or (5) by 
accidental transportation by farm hands, farm animals, or large 
insects. 
The control of the red spider is possible either by preventive or by 
repressive measures. Great expenditures of time, labor, and material, 
however, are necessary when the latter operation is undertaken. 
Measures of prevention are far more economical and practical. 
Clean culture, or the extermination of weeds and plants which breed 
the pest, is by far the most vital means of prevention that can be 
applied in the case of field and truck crops. 
In cases where cotton is grown within 100 yards of dooryards con- 
taining violets and other ornamental plants a careful watch of these 
plants should be maintained in crder that they may be sprayed or 
destroyed. 
By the persistent maimtenance of a finely pulverized surface mulch 
in fields the progress of migrating mites is somewhat retarded and the 
development of infestation correspondingly discouraged. 
Although the fertilization of cotton land in no way interferes with 
the status of the red spider, and exerts no direct controlling effect on 
infestation, yet the judicious use of fertilizers assists the plants to — 
overcome injury. 
Trap crops, rotation, favorable planting time, irrigation, etc., are 
either of only slight or of negative value. : 
Dispersion may be prevented by eliminating the plants in a field 
which harbor the initial infestation. This may be accomplished by 
pulling the first few plants which show infestation, or, in case the pest 
has secured a good foothold, the elimination will be accomplished 
only by means of plowing up all the affected portion of the field. 
In either case the stalks should be quickly piled and burned with the 
help of a little straw or light trash. 
Spraying for red spiders is effective if it is done with extreme care. 
There are a few sprays which will give complete mortality when prop- 
erly applied, but a second spraying is necessary to kill the ndwiduals 
that were eggs at the time of the first spraying. A contact insecticide is 
absolutely necessary, and it is vital that every leaf on an infested plant 
should be reached by the spray. 
