Insect Pests and Fungoid Diseases. 



431 



attack is noticed. Dress the ground where they have grown and for some 

 distance outside the margin with gaslime, and disinfect all tools and other 

 implements or articles which have come in contact with the soil during the 

 process of lifting. Avoid planting potatoes on this ground again for several 

 years, and before planting again dress the tubers with flowers of sulphur, 

 which should also be worked into the ground at the rate of 3 or 4 ozs. to the 

 square yard. 



" Greening " tubers intended for seed by exposure to light in the autumn, 

 and then boxing them for sprouting, has been shown to give some degree 

 of immunity to the disease. 



"Snowdrop," "Maincrop," and "Conquest" are varieties which have been 

 proved by experiment to be more resistant than others to Black Scab. 



POTATO "DISEASE" Blight or Rot (Phytophthora infestans). 

 This is the commonest as well as the most destructive disease to which 

 potatoes are subject. It is known to growers as the potato disease, and 

 not without good reason, for whilst other diseases to which the potato is 

 subject are only occasional incidents this is always present to a greater or 

 less degree, ready to play havoc with any unprotected crop in a season 

 favourable to its development, and 

 must therefore always be taken 

 into the reckoning. It is always 

 the most destructive in wet seasons 

 and especially so if the wet is ac- 

 companied by what is known as a 

 "close" or "muggy" condition of 

 the atmosphere. 



The first sign of its activity is 

 indicated by brown patches on the 

 leaves and stems. If left un- 

 treated these patches or spots 

 rapidly increase in size, the leaves 

 curl, the colour becomes darker, 

 until finally the whole plant, in- 

 cluding the tubers, is enveloped 

 and becomes rotten. 



The disease is caused by a fungus 

 which develops great numbers of 

 spores ; these are scattered by the 

 wind or by anything which dis- 

 turbs the foliage, and as every 

 spore which settles upon a damp 

 potato leaf is capable of forming a 

 new centre of infection the disease spreads with startling rapidity. 



^Treatment: To obtain sound crops of potatoes with any measure of 

 certainty the culture should be undertaken with the clear understanding 

 that the disease is always lurking about, and that the extent of its ravages 



Diseased Leaf and Tuber of Potatoes. 

 (Reduced.) 



