KERXEL-SPOT OF THE PECAX AXD ITS CAUSE. 11 
ANALYSIS OF RESULTS. 
Of the 313 nuts confined with bugs in the field and 17 in the 
laboratory (a total' of 330), 323 had typical kernel-spot and most 
of these, especially the Curtis, were very severely spotted. Of the 
91 checks in the field and 15 in the laboratory, totaling 106 nuts, 
all were entirely free from any evidence of kernel-spot. The results 
reported seem to leave little doubt as to the association of pecan 
kernel-spot with sucking insects, therefore confirming the investiga- 
tions of Turner (6). 
It has been suggested that the insects involved may possibly trans- 
mit with their piercing mouth parts some microorganisms to the 
pecan kernels which cause the characteristic spotting effect. With 
this supposition in view, the cultural work in the laborator}- was 
carried out. Of portions of over 400 separate spots that were 
planted on beef and corn-meal agar, more than half proved to be 
sterile. Hand's Coniothyrium was not observed in any of these 
cultures. If either a fungus or a bacterium was responsible for the 
spotting, it is logical to assume that a large percentage of cultured 
kernel spots would in suitable media develop the causal organism. 
Cultures from affected kernels have shown that most of the spots 
are sterile, while among those developing fungus or bacterial growth 
no single type of organism has been found constantly associated with 
the diseased condition. Furthermore, typical kernel spots can be 
produced readily by confining stinkbugs with immature pecans. It 
is, therefore, also logical to conclude that pecan kernel-spot can be 
d'rectry attributed to injuries inflicted by sucking insects, in this case 
to the southern stinkbug (Xesara viridula) . The pathological result 
may be caused by the mechanical rupturing of the host cells, by the 
sucking up of plant juices, by injection of toxic substances into 
the tissues, or by the combined result of all three types of injury. 
Xo study was made to determine the pathological effect of the punc- 
tures, but Figure 5 would lead one to suspect that the injury is due 
to the extraction of juices from the tissues affected and to the me- 
chanical injury of the cells. 
CONTROL MEASURES. 
The writer has done no work in view of demonstrating the practi- 
cability of controlling pecan kernel-spot. Dr. C. A. Van Duzee, an 
extensive pecan grower of Cairo, Ga.. has been practicing clean culti- 
vation in his orchard for several years. He reports that since this 
practice was adopted his nuts have been free from kernel-spot. 
It is the writer's opinion that clean cultivation can not be recom- 
mended unless stable manure can be supplied to the orchard soil 
