20 BULLETIN 148*, U. S. DEPARTMENT OF AGRICULTURE 
cotton growers, on account of the sterility of the plants and the 
resulting low yields. 
Since the first description of the disorder by Cook, in 1923, its 
occurrence over a wider range of cultural conditions has afforded evi- 
dence that the crazy-top injuries are closely associated with unfavor- 
able cultural conditions which produce stress effects in the plants. 
Although there are symptoms which are distinct from any of the 
ordinary stress conditions observed in cotton plants in other regions, 
the extent of injury is so definitely determined by the conditions 
that cultural methods are indicated as a practical treatment for the 
disease. 
A comparison of areas cropped to cotton for several years with 
adjoining areas where cotton followed alfalfa showed either a com- 
plete absence of the disease or only a few slightly affected plants on 
the land previously in alfalfa, while the areas cropped continuously 
to cotton showed a large proportion of affected plants, many of which 
were seriously deranged. 
The recovery of disordered plants when favorable growing condi- 
tions were restored and the failure of preliminary attempts to inocu- 
late healthy plants indicate that the disease is of such a character 
that its development is caused by poor cultural conditions rather 
than by infection. Although the close relations with stress conditions 
suggest that the disease may prove to be of a physiological character, 
careful study should be given to the possible existence of an infective 
principal whose injurious effects may be in evidence only when the 
plants undergo stress conditions, although definite injuries may be 
shown in plants that grow to large size before the end of the season. 
The association of the more striking and serious injuries with 
cemented soils, impervious soil strata, steep grade of land, and areas 
continuously cropped to cotton for several years would indicate that 
these factors have some influence on the incidence of the disease as 
well as on its severity, but do not offer conclusive evidence regarding 
the nature of the disease. 
Fewer diseased plants and milder symptoms were observed on the 
outside rows and at the lower end of fields with steep gradients than 
on the inside area, indicating that an increased supply of moisture or a 
more regularly available supply was a controlling factor in such fields. 
Eotation with alfalfa or modified methods of irrigation which bring 
about deeper penetration of water and a more constant supply of 
available moisture in the lower root zone would appear to be the most 
practical measures for controlling the disease. 
