VEGETABLE GROWING IN NEW SOUTH WALES. 101 



Early Blight of Potato. 



The fungus, causing this disease may attack the plants at anjr stage of their 

 development. The disease usually appears first on the lower leaves, in the 

 form of small brown or black spots, which later increase in number and size, 

 becoming irregularly circular in outline, and often exhibiting concentric 

 markings. Sometimes the spots may fall out, producing a " shotbole " 

 appearance. The leaves eventually curl and die. Brown or black spots, 

 more or less circular and slightly depressed, may develop on the stem. 



The disease does not damage the tubers, but by destroying the haulms, 

 decreases the yield. Abundance of spores are produced on the dead spots 

 and spread the disease. The fungus probably passes from one season to 

 another on old diseased parts of the affected plant. 



In the control of this disease the destruction by burning of all parts of 

 old plants is the first consideration. Very often after a crop the refuse of 

 old plants is turned under, and in this way a resting place is afforded for 

 the fungus. Spraying with Bordeaux mixture (see page 128) should be 

 regularly carried out to prevent infection. If the disease is serious in any 

 year a rotation should be practised, but potatoes should not follow nor 

 precede the tomatoes. 



Early Blight of Tomato. 



The appearance of this disease on the stems and leaves is similar to that 

 described for early blight of potato. With the tomato, however, the fruit 

 also may be attacked, either while on the plant or after picking ; brown or 

 black spots appear on the surface and the disease may grow into the interior 

 of the fruit and rot it. 



For control measures, 'see early blight of potato. 



Late or Irish Blight of Potato. 



This disease may attack any portion of the plant; and may appear at any 

 stage of its growth. The leaves become yellowish-green in colour, and then 

 irregular brown patches are developed, commencing at or near the tips and 

 edges. On the under surface of the leaf, these are seen to be surrounded by 

 a delicate white or -greyish mould. 



If the weather remains cool and damp, the patches rapidly enlarge and 

 turn black, the plants then appearing as if they had been killed by frost. 

 Finally the whole plant wilts, becomes black and rapidly decays. 



If a warm dry spell occurs soon after infection the disease is checked, the 

 brown spots do not then enlarge, but become brittle, crack, and dry up. The 

 tubers are sometimes attacked by spores of the fungus which are washed 

 through the soil by rain. Tomatoes and potatoes are often grown in the same 

 area, and thus the fungus finds a living host throughout the whole year. 



The most satisfactory control measure consists of systematic and thorough 

 spraying before the appearance of the disease, with Bordeaux mixture (see 

 page 128). It is also advisable to use seed from a crop which has been free 

 from the disease. 



