BULLETIN 1102, U. S. DEPARTMENT OF AGRICULTURE. 



SUPPLEMENTARY EXPERIMENT. 



On September 15, 1921, 12 clusters of Curtis nuts were brought 

 into the laboratory and placed in lantern-globe cages. Short stems 

 were left on the ckisters which were inserted in bottles containing 

 water. Each cage had a strip of cheesecloth tied over its top. 



From five to seven specimens of adult southern stinkbugs were 

 placed in each of six of these cages. The other six clusters were 



reserved as checks, 

 but were subjected 

 to the same condi- 

 tions, except that no 

 bugs were confined 

 with them. 



On September 18, 

 or approximately 65 

 hours later, all the 

 nuts were opened and 

 examined. Of the 

 17 nuts confined with 

 bugs, each had from 1 

 to 12 typical kernel 

 spots. Of the checks, 

 numbering 15, not the 

 slightest evidence of 

 kernel-spot was found 

 on any. Cultures 

 were made on beef 

 agar from 10 spotted 

 nuts of the first series. 

 No growth of any 

 kind was produced 

 from these cultures. 

 This test alone would seem to prove that pecan kernel-spot is 

 caused directly by the stinkbugs feeding upon the kernels or by in- 

 jecting toxic substances into the tissues. It also indicates very 

 strongly that the Nezara bugs do not regularly transmit parasitic 

 microorganisms to the pecan kernels with their piercing mouth 

 parts. 



LABORATORY CULTURES OF KERNEL-SPOT. 



Owing to the porous structure of the kernel-spots and their tend- 

 ency to quickly absorb liquids, the method of soaking diseased 

 plant tissues in a solution of mercuric chlorid in preparation for 

 making cultures was found to be impracticable. The following 

 method was used, giving very satisfactory results : 



Fig. 5. — Southern stinkbugs {Tsezara viridula) on pecan 

 nuts of the Curtis variety. (Natural size.) 



