RED SPIDER 
( Tetranychus 'bimaculatus Harvey) 
Life History and Injury 
The mites known as red spiders are so small that they can hardly be 
seen without the aid of a magnifying glass. They may be greenish 
or yellowish in color, but the females are usually reddish and the smaller 
males reddish yellow. Red spiders are found throughout the Cotton 
Belt and feed from June to September on almost 200 kinds of plants, 
including many garden and field crops, ornamentals, and weeds. In 
the South they pass the winter on leaves that remain green, such as wild 
blackberry, Jerusalem-oak, wild vetch, and violet. The red spiders 
move to cotton early in the summer, and when cotton is no longer suit- 
able for food they return to weeds or other plants. They crawl on the 
ground and are carried by wind or by rainwater. Red spiders multiply 
rapidly and may have as many as 17 generations a year. Hot, dry con- 
ditions are most favorable for rapid multiplication, and a heavy rain 
often checks an outbreak. Red spiders live on the under side of the 
leaves, where they lay their eggs and spin delicate webs. They suck 
the sap from the leaves, the under surfaces of which become thickly 
dotted with whitish feeding punctures. Red spider injury is often 
called “rust.” It is first indicated by blood-red spots on the upper sur- 
face of the leaves. The entire leaf then reddens or turns rusty brown, 
curls, and drops from the plant. The loss of leaves causes shedding of 
small bolls and may prevent the lint from developing properly in large 
bolls. Damage is more serious in the Southeast, but occurs in all cotton- 
growing States. 
Control 
Preventing the spread of red spiders to cotton by destroying weeds 
around the fields and by controlling the pest on dooryard plants is of 
first importance. Pulling out and destroying the first few cotton plants 
that become infested often stamps out an infestation. Dusting cotton 
with finely ground sulfur at the rate of 10 to 25 pounds per acre is the 
most practical direct-control measure. Satisfactory control is also 
obtained by spraying with the following insecticides: (1) Potassium 
sulfide (1 ounce in 2 gallons of water) ; (2) lime-sulfur (home-made or 
commercial) ; (3) kerosene emulsion (2 gallons of kerosene and % 
pound of soap to 12 gallons of water) ; 1 and (4) flour paste (cook 1 
pound of flour in 1 gallon of water until smooth and add 12 gallons of 
water). A second application a week later is necessary to kill the red 
spiders that have- hatched since the first application. Care should be 
taken to cover the under side of the leaves thoroughly with the dust or 
spray. 
1 To make a kerosene emulsion take 1 gallon of soft water, one-half pound of laundry soap, 
and 2 gallons of kerosene. Dissolve the soap in the water by boiling, add the kerosene 
immediately on removing the soapy water from the fire, and pump the mixture vigorously 
for about 10 minutes through a spray pump into another container. For spraying cotton, 
this stock mixture should be diluted with 12 gallons of water. 
April 1946 U. S. Government Printing Office 
For sale by the Superintendent of Documents, Washington 25, D. C. Price 5 cents 
684387—46 
