TOMATO DISEASES. 
169 
TOMATO DISEASES. 
By W. Bewley, D.Sc, Director of the Lea Valley 
Experimental Station. 
[Read November 15, 1921 ; Mr. W. A. Bilney in the chair.] 
Of all crops grown under glass, the tomato is probably one of the 
most susceptible to disease. In districts where large areas are 
devoted almost entirely to the cultivation of this plant under com- 
mercial conditions, the losses caused by disease amount to many 
thousands of pounds. To those who realize the high cost of 
production of this crop, the importance of controlling all diseases, 
which are slowly but surely reducing the growers' profits, is obvious. 
The Experimental and Research Station, situated at Cheshunt 
in Hertfordshire, is placed in the heart of the great tomato-growing 
industry which has spread along the valley of the Lea. At this 
station, problems connected with the cultivation and diseases of 
tomatos and other glasshouse crops are being investigated, and it 
is the aim of this paper to describe the many diseases which have 
been studied there. 
From the time the young plant emerges from the seed until the 
gathering of the last fruits, the tomato may be attacked by one 
disease or another. One of the earliest of these is that popularly known 
as " Damping off " (fig. 46) of the seedlings. In this case the young 
plants, while still in the seed-box and barely an inch in height, are 
attacked by a fungal parasite at the ground level. The tissues soften 
and collapse and the seedling falls over. At times the plants may escape 
infection in the seed-box, but may be attacked after being potted 
into " 60 " pots or even when planted out in the house, when the 
disease is generally known as " Foot Rot " or " Blackleg." (Fig. 46.) 
The disease is caused by a number of different fungi, but mainly 
those belonging to the genus Phytophthora and especially Ph. 
cryptogea Pethybridge and Ph. parasitica Dastur. The disease 
organisms aire carried from one season to another in the soil, water, 
seed-boxes, and pots. They are not present in all soils, but exist 
as a definite infection in some. Infected soil is readily cleansed 
by sterilizing with steam, formaldehyde, or by baking ; infected 
seed-boxes and pots by sterilizing with steam or formaldehyde ; and 
infected water by thoroughly renovating, cleaning, and deepening the 
well. The great importance of having a pure water supply cannot 
be too firmly impressed upon the minds of all cultivators of plants, 
for all methods of sterilizing soils must be useless if copious infection 
is carried with each watering. In 1920 the writer and Mr. W. 
Buddin, M.A.,* made an extensive examination of nursery water 
* For a full account of this investigation see Annals of Applied Biology, 
vol. viii. No. 1, June 192 1. 
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