14 BULLETIN 1102, U. S. DEPARTMENT OF AGRICULTURE. . 
Arthur and Bolley (1) who concluded that the disease Avas caused 
by a bacterium. In the case of pecan kernel-spot, Rand first con- 
cluded that the trouble was caused by a fungus, and it is now proved 
by the writer to be caused by insect punctures. 
Since the initial cause of pecan kernel-spot is entomological and 
the result pathological, control measures can possibly best be worked 
out by considering both factors. 
SUMMARY. 
Pecan kernel-spot has been reported from North Carolina, South 
Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and 
Texas. 
Owing to the fact that the spots can not be seen until the shells of 
the nuts are removed, and also because pecans from planted orchards 
are usually widely distributed in small quantities to consumers, the 
extent of the loss caused by kernel-spot is difficult to estimate. While 
the nuts in some orchards will be entirely free from this disease, in 
other orchards such a large percentage of the nuts will be spotted 
that the crop will be unmarketable. 
Rand conducted a laboratory investigation of kernel-spot in 1912- 
13 and concluded that it was caused by C oniotkyrium caryogenum. 
The result of the work of Turner in 1917 indicated that the spots 
were caused by punctures of insects. 
In the present investigation, 250 clusters of Schley and Curtis 
pecans were incased with wire cages. From five to seven specimens 
of southern stinkbugs (Nezara viridula L.) were confined in 200 
cages during a period of approximately five weeks for the Schley 
nuts and two months for the Curtis. Fifty clusters Avere caged as the 
others, but no bugs were placed in them. These served as checks. At 
the end of the experiment none of the checks showed any signs of 
kernel-spot. Of those nuts caged with bugs. 97.6 were spotted with 
typical kernel spots. 
Nuts with which bugs were confined in a laboratory developed 
typical kernel spots within 65 hours. No microorganism developed 
from these spots in Petri dish cultures. 
Of 416 cultures made of kernel spots, 80 developed colonies of 
bacteria, 71 grew fungi, and 265 remained sterile. 
No one organism was found constant in pecan kernels affected with 
kernel-spot. Eight species of fungi and three of bacteria were iso- 
lated in this experiment and considered to be saprophytic. 
All 11 forms isolated from affected kernels were inoculated into 
healthy pecans. None produced spots resembling typical kernel-spot. 
The cause of pecan kernel-spot is attributed entirely to the me- 
chanical rupturing of the host cells, to the sucking of the plant juices, 
to the injection of toxic substances into the tissues, or to all three 
types of injury. 
Possible control measures are suggested. 
