THE RED SPIDER ON COTTON. 61 
We feel that we can say that among the cotton strains the old 
Peterkin group is probably most susceptible. 
An experiment was conducted in testing the value of thickly broad- 
casting cotton at the boundary of a field as a trap crop for red spiders. 
The cotton was sowed between the cotton field proper and a large, 
heavily infested border of violets. The broadcasted cotton became 
infested and was plowed in before there was danger of a second 
migration to the crop proper. As a result the field remained free 
from mites. Although we do not recommend the broadcasting 
measures as an important method of prevention, still the success of 
this experiment would indicate strongly that the cotton trap crop is 
practicable as an auxiliary expedient to be used in controlling this 
pest. 
It has been surmised that wide spacing of the stalks, thus prevent- 
ing the interlacing of branches, would prevent the spread of the red 
spider through a field. Experiments at Batesburg have shown that 
the red spider disperses through a cotton field commonly both by 
means of the ground and the interlacing branches. While this shows 
the futility of the wide spacing as a complete preventive, it seems 
reasonable to suppose that the movement of the red spider will be 
somewhat impeded; in fact, we can corroborate this supposition to 
some extent in that infestation was observed to spread very slowly 
in certain checked fields. 
Since the movements of nearly all insects, when crawling over the 
eround, are retarded by pulverized soil, it appeared that by maintain- 
ing a dust mulch in exposed cotton fields the progress of the migrating 
mites would be checked. In the case of the ‘‘check”’ cotton fields, it 
was possible to maintain continually a thoroughly pulverized soil sur- 
face. It was observed that the infestation in these fields progressed 
very slowly and failed to become at all threatening. In fields culti- 
vated in checks it is easy to see that leaf-to-leaf dispersion will be 
ereatly restricted and, at the same time, ground travel somewhat re- 
tarded. Thus, by combining these two measures—spacing the plants 
and niaintaining a surface mulch—much good will doubtless result. 
In the cultural experiments conducted, both the ordinary sweep 
and the spring-tooth adjustable cultivator have been employed. 
The latter implement creates a much better surface mulch than does 
the: old-type sweep. 
Early planting permits the plants to develop a maximum growth 
of foliage and fruit by the time mites appear m large numbers, which 
is important, inasmuch as plants of considerable size are rarely killed 
by the pest, nor are well-advanced bolls commonly shed from red- 
spider infestation. Early planted cotton ages and soon toughens, 
making it untempting to the red spider at a time when later cotton. 
offers ideal feeding conditions. Late cotton is almost always objec- 
