VEGETABLE GROWING IN NEW SOUTH WALES. 93 



where possible. Heavy dews are also necessary for the spieacl of the disease, 

 and by planting on higher and more exposed levels less subject to dew the 

 spread may be prevented. American horticulturists claim to have produced 

 a variety which is resistant to the disease. This distinction does not yet 

 apply to any variety at present in cultivation here. 



/ 



Black Leg of Cabbage and Cauliflower. 



This disease occurs on cabbages and cauliflowers, especially when young. 

 Infection frequently takes place on the stem at the surface of the ground, 

 just bebw the junction of the leaves, and also at the margins of the leaves. 

 The disease spreads downwards to the roots and around the stem, often 

 completely girdling it, giving it a black appearance hence the name. 

 Often the fibrous roots and the lateral roots are killed. Before the plant 

 dies, a purplish tint is developed in the foliage, and persists until the plant 

 dies. Wilting of the plant is very characteristic, the leaves adhering to the 

 stem and drooping. Sunken spots occur on the leaves, and later these dead 

 areas become covered with numerous, minute black specks. The fungus is 

 harboured for the most part in the soil on decayed steins and leaves of plants. 



The best control measures are preventive ; all refuse of present and past 

 crops should be collected and burnt. 



Seed-beds can be sprayed with weak Bordeaux mixture (see page 128), and 

 only clean seedlings should be planted out. 



Blaek Leg of Potato. 



This disease, also called black stalk rot, has been met with once in New 

 South Wales, and it also occurs in Victoria. The seed tuber begins to rot 

 early, sometimes before the sprouts break through the ground. The rot 

 spreads up the base of the stem, which turns quite black, shrinks, and rots 

 as far as the surface of the soil, and often above it. This is the best indica- 

 tion of the disease. As a result of this injury, the whjle plant begins to die,, 

 generally without setting any tubers. Wet and cold weather apparently 

 favour the disease. Other plants, such as turnips, swedes, carrots, and 

 parsnips are also attacked. As it is practically confined to the underground 

 parts, the disease may be greatly controlled by carefully digging out and 

 burning all diseased plants." Selection of seed and dipping in formalin 

 as recommended for Rhizoctonia (page 106) also assist in preventing its 

 introduction. 



Black Rot of Cabbage and Cauliflower. 



This disease, popularly known as black rot, but sometimes as dry rot 

 brown rot, black stem, black vein, &c., is a bacterial one. Cabbage, cauli- 

 flower, kale, kohlrabi, turnip, swede, and radish are all liable to attack, but 

 the following account refers more particularly to cabbage and cauliflower. 



