Plant Diseases in the Western Provinde, 525 



PLAMT DISEASES IN THE WESTERN PROVINCE. 



Notes by Y. A. Putteeill, M.A., Division of Botany. 



Chlorosis in Kelsey Plums. 



During the month of October, 1920, Mr. Rowland Taylor, of 

 Wellington, Cape Province, drew my attention to a fairly large block 

 of twelve-year-old Kelsey phim trees badly affected with cldorosis. 



For those to whom this term is unfamiliar, I might mention 

 that chlorosis is an abnormal condition of plants whose foliage is 

 normally green and healthy looking, but in affected plants assumes 

 a yellow colour owing to the non-formation of chlorophyll, the green 

 colouring matter which gives that familiar colour to vegetation. 

 Chlorophyll is of paramount importance to the life of plants. It 

 captures energy from the sun's rays, enabling the tissues in which it 

 is present, by means of this imprisoned energy, to make use of the 

 carbon dioxide (carbonic acid) in the air, and build it up into plant 

 foods. It will be readily understood, therefore, how vitally important 

 it is for plants to be grown under conditions favourable for the 

 chlorophyll. Various conditions have been shown to be essential for 

 its production : light (this factor is certainly not lacking at 

 Wellington), iron in the soil, and generally satisfactory conditions 

 of nutrition. 



The block of trees in question is on a good slope, and is very well 

 drained. As too great acidity in the soil is very common in the 

 Western Province, I made a qualitative test for acidity in soil 

 taken from around the feeding roots of a badly attacked tree. The 

 tests showed that the soil was slightly acid. The root system of a 

 badly affected tree was examined, the whole tree being dug out. 

 There was no indication of parasitic attack, and this was confirmed 

 by microscopical examination of the roots. 



Apricot trees in the same block were slightly affected though not 

 nearly as badly as the plum trees. 



I am much indebted to Dr. Juritz, Agricultural Research 

 Chemist, Capetown, for making a complete analysis of two samples 

 of soil taken at levels of 6 inches and 12 inches below the surface 

 respectively, and close to a diseased tree. As his remarks On the 

 results of his analysis will be of interest to Western Province fruit 

 growers, I will give them here in full: — - 



*' It is noticed that, according to your remarks which 

 accompanied the samples, the orchard is on a good slope and well 

 drained; the surface soil, to a depth of 18 inches, consists of coarse 

 sand wherein the feeding roots are located, the sub-soil below the 

 above depth being clay. 



" Two samples of soil were received, one (No. 1) taken at a depth 

 of 6 inches, the level of the feeding roots, and the other (No. 2) at a 

 depth of 12 to 15 inches, both of them, therefore, above the level at 

 which the clay begins. 



