CRAZY-TOP DISORDER OF COTTON 5 
disease, so that the crop is thrown off earlier and more top growth 
is formed later in the season. 
SPOT OCCURRENCE OF THE DISORDER 
The first appearance of crazy-top in a field of cotton is usually noted 
9 in rather definite spots (pi. 1 and figs. 1 and 2), but if cotton is grown 
continuously, in subsequent years the area occupied by diseased 
plants often becomes more extensive, and in some cases the disorder 
spreads throughout the entire field, affecting a large percentage of 
the plants. The original spots of the disease can usually be identi- 
ty ooo ooooooooo •ooooooo ooo o 
oooo OO 6*0 0» • O OO OOO 
oo ooo ooooooo o o • • • o o .o ooooo ooooooo 
©••©••oooo «0 •••••••• #00 ooooo ooooo 
ooo oo »o • oo# •:••••••• ••• • •••• • o o oooooooo 
oooo OOO Ml* ••••••••• ••• • • • •• o ooooo 
ooooooo ::*«•♦••«#« • ••• •••••oooo o 
oooooooo ••• •• • •••oo»»»«»oo oo 
OOOOOOOO OOOO • O O •• • • • ©00 • o ooooo oo 
000 00 • •oooooooooooo 
ooo oooooo • ooooooooooooooo 
ooooo oooo ooo ooo 00 oooo 00 ooo oooo 00 o 
Fig. 1.— Diagram drawn to scale, showing a small definitely outlined spot of plants affected by 
crazy-top in a field of Acala cotton. 0= Normal plant, ©= crazy-top plant 
fied in later years by the more pronounced symptoms. Other spots 
may appear with equally severe symptoms, but after a field has been 
affected for two or three years the diseased areas generally have 
less definite margins and affected plants are found mixed indiscrimi- 
nately among normal plants, unless abrupt soil changes occur. Where 
efforts have been made by the growers to improve the cultural con- 
ditions of badly affected fields by such methods as heavy irrigations 
and continued cultivating, the prevalence of the disorder and the 
degree of injury of the affected plants have tended to diminish. 
A spot of crazy-top in a field of Acala cotton is shown by diagram 
in Figure 1. The limits of the affected area are seen to be rather 
definitely marked, and all the plants in the central portion of the spot 
