pte Stag 
62 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
tionable to the farmer, since in ordinary seasons it results in a reduc- 
tion of the yield, and because of the fact that it suffers heavily in the | 
eventof the appearance in the late summer of the bollworm, or the 
leafworm, or of the boll weevil western sections. 
We have made an effort to establish the rotational value of the 
common crop plants, garden plants, and field plants, both by planting 
them in or near infested fields and by making frequent examinations 
of agreat many of these plants which happened to be planted by others 
in infested localities. Besides cotton, we have found red spiders 
commonly upon the following field crops: Cowpeas, vetch, red and 
white clover, alfalfa, corn, hops, beets, and watermelon. They also 
have been found frequently upon the following garden crops: Pea, 
bean, onion, tomato, pepper, Irish potato, sweet potato, lettuce, 
okra, turnip, mustard, radish, cabbage, squash, beet, celery, straw- 
berry, and several others. Our host list also included many of the 
common bush fruits, tree fruits, and dooryard plants. Rather acute 
cases have been seen on corn, cowpeas, and sweet potatces. The 
only plants which have appeared largely immune are the grasses 
and the small grains. Owing probably to the lack of shelter, which 
the foliage of the grasses exhibits, the mites are unable to maintain 
themselves under severe weather conditions. The planting of grains 
on land normally heavily infested is therefore a measure which 
should be considered by the farmer. 
REPRESSIVE. 
That it is possible to eradicate the pest from infested fields has. 
been demonstrated, but in many cases the task is so tedious that 
only the most determined farmers will resort to the necessary meas- 
ures. 
The experiment has been tested frequently of pulling up and 
destroying the first few plants which show infestation. In applying 
this measure the farmer must maintain a constant surveillance of 
suspected fields, so that the earliest affected stalks may be detected. 
In such cases the operation will probably have to be repeated several 
times, owing to the fact that certain plants are overlooked during the 
first examination because the colonies on them are too young to 
have revealed their presence. Great care should be observed in 
locating every plant which shows the characteristic red spots, and 
these must be carefully taken from the field and burned. This 
must be done before infestation has reached the pomt where there 
is danger of a secondary dissemination, and before there is liability 
of the dropping of infested leaves. 
If infestation has spread until a considerable area has become 
involved, more drastic steps will have to be taken. It is sometimes 
advisable, where a continuous area of infestation occurs In a large 
