Departmental Activities. 399 



BOTANY. 



Internal Brown Fleck in Potatoes is a very serious trouble with 

 which potato growers on the high vekl have to contend. Affected 

 tubers are externally sound, but occasionally, when there are brown 

 flecks near the surface of the tuber, tbese show through to the surface. 

 Such cases are comparatively rare, and by this characteristic tubers 

 affected with internal brown fleck can be readily distinguished from 

 those attacked by Irish potato blight or late blight which also causes 

 a brown discoloration of the tuber : in the latter cases the discolora- 

 tion is always near the surface and causes depressed areas on the skin 

 of the tuber which can readily be detected without cutting it. 



Tubers affected by internal brown fleck keep well, which is 

 another point of difference from those attacked by fungous diseases, 

 and are as a rule quite free from external discoloration. When 

 affected tubers are cut across, however, they show brown flecks in the 

 otherwise sound flesh. These vary in size from a pin's head to about 

 one-third of an inch in diameter ; they may be very numerous, or 

 only two or three may be discernible in a section through a tuber. 

 In any case the edible qualities of the potato are impaired, as the 

 brown specks remain quite hard when the tuber is boiled and can be 

 picked out from the soft part of the flesh. The spots are scattered 

 and correspond with those of potatoes aff'ected with " internal 

 disease " rather than with " streak." 



If an affected tuber be cut across and allowed to dry, the healthy 

 part of the flesh shrinks, but not the corky flecks, and these become 

 raised above the cut surface as they do not take part in the general 

 shrinkage due to loss of water. The same thing happens if pieces of 

 the tuber are dehydrated in alcohol. 



From the knowledge at present available it would appear that 

 this is a deficiency disease occurring for the most part in rather sandy 

 soils which are deficient in lime and available phosphates. It is our 

 intention to make further investigations into the cause and preven- 

 tion of fleck, and any farmers who are willing to co-operate are 

 invited to communicate with this Division. 



Quack Crass, a Troublesome Weed. — We have recently had 

 Agropyrum re pens (quack grass), also known as twitch grass and 

 conch grass, sent in for identification from Volksrust, where it is 

 reported as being a most troublesome weed in cultivated lands. 



Quack grass very much resembles rye grass in general appear- 

 ance. It has the same kind of inflorescence, grows to a height of two 

 or three feet and has narrow, rather long leaves. The long creeping 

 underground runners of the former, however, are entirely lacking 

 in the latter grass, and it is these that make quack grass such a 

 troublesome weed and so difficult to eradicate. In America, where 

 it is well known, it is said to make most excellent hay being both 

 nutritious and palatable, but at the same time, like our kikuyu, it 

 is a pest to cultivated lands where it is not wanted. The best way 

 to eradicate it is to plough early in spring, and then use a shovel - 

 toothed cultivator every three days through the growing season, 

 cutting off' all green shoots below the surface of the ground. A crop 

 such as mealies that can be easily cultivated should be planted, and 

 all green shoots of the quack grass persistently kept down. The 

 reason for this is that the long roots are fed by the green shoots, and 

 if their source of nourishment is cut off the roots must die. 



