KERNEL-SPOT OF THE PECAN AND ITS CAUSE. 



was of a serious economic importance in southern Georgia in 1916 

 and again in 1921. Some growers in northeastern Florida reported 

 an entire loss of their Curtis nuts in 1919 and 1920, but these same 

 Florida growers reported the loss to be slight in 1921. 



DESCRIPTION OF KERNEL-SPOT. ^ 



The spots are found only upon the kernels of the pecan nuts. Ordi- 

 narily no evidence of the trouble is apparent until the shell is 

 removed. The writer has observed that when nuts are punctured by 

 the Xezara before or soon after the nuts have attained their full 

 growth small sunken places will be formed in the shucks of the 



nuts. (Fig. 1.) 



Punctures may also be seen in the shell if an examination is made 

 while the nut is yet green. The pecan shell is greenish white until 

 the maturing processes start, and 

 during this stage punctures appear 

 as small brown spots less than 1 

 millimeter in diameter. These spots 

 can be followed through the shell 

 by shaving or scraping with a 

 knife, and a typical spot will 

 usually be found on the kernel 

 immediately beneath it. These 

 spots are not evident on the shell 

 after the nuts have matured and 

 developed the nut-brown color. 



The centers of the spots are always found upon the ridges or the 

 edge of the pecan kernels, and never in the creases or on the inside 

 surface of the halves of the kernel. (Fig. 2.) 



In almost all typical kernel-spots one will find a small papilla, or 

 pimplelike structure, in approximately the center of the spot. A 

 magnified cross section of a spot through this pimplelike structure 

 shows the epidermal cells and those cells lying immediately beneath 

 this point as being ruptured. (Fig. 3.) Undoubtedly this small 

 elevated place marks the point of entrance of the seta of the insect. 

 The kernel spots are usually but not always sunken below the surface 

 of the adjacent healthy tissues. They vary in size from 2 to 5 mil- 

 limeters in diameter. 



In color, the surface of the spots ranges from brown to black. In- 

 ternally the affected tissues extend in approximate hemisphere be- 

 neath the surface and are frequently separated from the healthy tis- 

 sues by a distinct brown layer. The internal part of the spots is 

 almost white, pithy and porous, and apparently is not discolored or 

 disorganized until organisms of decomposition gain admittance. The 

 spots are decidedly bitter, but this bitter taste is not imparted to 

 the unaffected portions of the kernel. 



Fig. 1. — A pecan nut of the Curtis 

 variety, showing indentations caused 

 by early punctures of 'Sezara virvd- 

 ula. 



