256 EXPERIMENTAL FAEMS 



2 GEORGE V., A. 1912 



vii. p. 286) who considers that it is caused by a ' chytridiaceous endophyte hitherto 

 undescribed.' Mr. Home's note is preliminary and has not at present advanced 

 our knowledge to any degree. It remains to be seen whether the organism will present 

 itself again and to other observers. At present the only suggestion that may be made 

 is the selection of varieties that remain free from any spotting of the described kind. 

 Affected tubers have again been secured and have been planted this season. The 

 results will be published in our next report. 



LEAF SPOT OR LEAF DLIGHT OF TOMATOES (Septorid LyCOpevsiti, Speg). 



This disease is distinguished from others attacking the tomato crop by the 

 characteristic ' spotting ' it produces. The spots are small, numerous, often angular, 

 with a dark border, the centre becoming paler with age. On the upper surface of the 

 leaf, in the centre of the older spots, will be found the minute fruit bodies, black when 

 mature. The disease begins on the tips of the lower leaves and gradually extends to 

 the younger ones and to the stems. Badly attacked leaves wither up and fall away and 

 the crop is seriously injured, the fruit often failing to set. The fungus probably 

 passes the winter in the crop refuse in or on the soil. We have also observed the 

 occurrence of these spots on the stem, petioles and unripe fruits of tomatoes. 



Control. 



Spraying with Bordeaux mixture is quite effective. The first application should 

 be made before transplanting. Subsequent applications should be made often enough 

 to keep the foliage protected and until there is danger of staining the fruit. The chief 

 difficulty is to do the work thoroughly with ' unstaked plants under field conditions. 

 It has also been found very useful, when planting out young tomato plants to dust 

 a little powdered fresh lime into the hole and around the plants. 



ONION MILDEW (PERONOSPORA SCHLEIDENI, UNG.) 



This is a common and destructive disease of the onion crop. Although we have 

 not received many inquiries about it during the past year, yet it is capable of becom- 

 ing such a serious enemy of the onion grower that we think it advisable to give a short 

 account of it. 



The disease may appear as early as June, but occurs usually later. It is detected 

 by the spore-bearing branches of the fungus giving rise to a velvety or furry appear- 

 ance on the surface of the leaf, together with a purplish colour. Later on, the leaf 

 collapses and withers or rots away. Summer spores are produced in great numbers 

 and, under favourable conditions, especially wet weather, the disease spreads very 

 rapidly. If the plant is young when attacked, it will succeed in producing another 

 crop of leaves and, if these can be saved, a fair or even a good yield may be obtained, 

 but if nothing is done these later leaves meet the same fate as the earlier ones, and the 

 plant is either killed outright or the yield seriously reduced. Another kind of spore 

 adapted for carrying the fungus over the winter {oospore) is produced in the tissue 

 of the dead leaves and these resting spores, by the rotting of the leaves, are set free in 

 the soil, or in the manure heap if any of the crop refuse is carelessly thrown there. 

 From these spores comes the first infection of the succeeding year. 



