PLANT DISEASES. S3 



may under favourable conditions, produce another form 

 of fruiting of the fungus is of some practical interest. 



(3) A " Blossom- Wilt " of pear trees, apparently caused 

 by a Brown Rot fungus, is under investigation. 



Glasshouse Pests. 



Experimental and Research Station, Cheshunt, Herts. 



" Damping off" of tomato seedlings and " Foot Rot " of young 

 plants. — In a bad year this disease is estimated to cause a loss 

 of between £6,000 and £8,000 in the Lea Valley district. Coming 

 as it does at the beginning of the season, it is a considerable 

 source of anxiety to growers. In the seed-boxes, the young 

 seedlings are attacked at the base, and the rapid collapse of 

 the stem tissues causes the seedlings to fall over. Sometimes 

 the young plants are attacked in the same way after " potting 

 up " or even " planting out " ; in this case the disease is known 

 as " foot rot." The disease was investigated at the Station, 

 and it was shown that the parasitic organisms concerned were 

 distributed in the pots and boxes, soil and water. It was found 

 that the steriHsation of soil, boxes and pots by baking, steaming, 

 and a 2 per cent, solution of formaldehyde, and the use of a 

 clean water supply, proved a sure way of prevention. Growers, 

 however, also desired some means of checking the progress of 

 the disease should it actually appear during the growing season. 

 A fungicidal soil compound was therefore devised, and this 

 mixture, which is known as the Cheshunt Compound, has proved 

 of great value. Copper sulphate (2 oz.) and powdered ammonium 

 carbonate (11 oz.) are intimately mixed, stored for at least 

 24 hours, and i oz. of the mixture dissolved in 2 gallons of water. 

 This solution may be watered on to growing plants without 

 injuring them in the least, and will at the same time destroy 

 the " damping off " organisms. It has been widely used with 

 satisfactory results. One tomato-grower, for example, had 

 replanted two houses four times and lost practically all his 

 plants each time. After applying the above solution to the 

 soil both before and after planting, he lost only four plants out 

 of 2,000. 



" Sleepy Disease " of Tomato. — This is caused by a fungus 

 Verticillium albo-atrum. The disease leads to extensive losses 

 each year (roughly £20,000 in the Lea Valley per year), especially 

 during cold seasons. Laboratory and glasshouse experiments 

 have shown that above an average day and night temperature 

 of 77° F. the diseased plants recovered. The physiology of the 



