108 VEGETABLE GROWING IN NEW SOUTH WALES. 



and to protect itself from further attack. Various conditions have been at 

 times suggested as the cause of scab, such as the presence of lime, ashes, 

 fresh stable manure, cinders or grit in the soil ; also the dryness of the 

 season and the nature of the soil (acid, alkaline, sandy, heavy > &c.). Where 

 experiments, carefully conducted with proper scientific precautions, have 

 been carried out, it is becoming evident that some living organism is always 

 the cause, and that the above- conditions may influence its growth. In New 

 South Wales the best known scab producers are eelworms, and also the 

 fungus Rhizoctonia. 



Sclerotium Disease of Beans and Peas. 



A disease that is common to very many different plants, including beans 

 and peas, is that" known as sclerotium disease. It attacks the stems, com- 

 mencing as a white mould at the ground line and working upwards. After 

 the fungus has developed for some time the leaves become yellow and wilt, 

 and finally the stem collapses owing to the fungus blocking up all the water- 

 conducting channels. When the stem of the plant is hollow the fungus is 

 produced in considerable quantity in the cavity, and forms numbers of lumps 

 that are white at first, and then black, externally. These lumps vary in size 

 up to that of a pea, and- form a resting stage of the fungus. They remain 

 either free in the soil, or in decaying plants, and in the spring, develop small, 

 brown, mushroom-like growths on long stems, which produce spores that are 

 able to infect a new crop. 



Diseased plants should be burned and not allowed to Jie on the ground. 

 The ground should be well limed, and the succeeding crop should be plants 

 of .a different family to that affected. 



Soft Rot or Ring Rot of Sweet Potato. 



This is not a serious field disease, though it occasionally occurs when wet 

 conditions prevail at the time the plants are dug. However, it often causes 

 much damage in forcing-beds and in storage. The symptoms of attack are a 

 rapid softening of the whole potato, which on squeezing exudes a brown 

 liquid. Sometimes only a dark ringed area is produced in the root. White 

 tufts appear on the outside of the potato, and on these a number of black 

 specks (the fruiting bodies of the fungus) are produced later. Rotted 

 potatoes are soon invaded by other organisms, and become an evil-smelling 

 disintegrating mass. 



It is impossible to control this disease in the field before digging, but it is 

 lecommended that, before planting, the roots be treated with corrosive 

 sublimate (made up of 1 oz. of the chemical in 8 gallons of water), by 

 soaking them for ten minutes. Rather better results have been obtained with 

 this solution than with the formalin method. 



