64 DISEASES OF GLASSHOUSE PLANTS 
the top of the plant to fall over. The disease organisms 
enter the plant via the roots or a leaf touching the soil. 
In the former case the fungus passes rapidly up the stem, 
and ultimately causes the collapse of the tissues at some 
definite part. ‘This collapse usually occurs at or near to 
the soil level, but many cases have been examined where 
the constriction appeared at a height of twelve to sixteen 
inches above ground, whereas in other cases the root is 
destroyed and separated from the upper portion of 
the plant. Generally speaking, this fungus rapidly kills 
the plant, and the losses caused are considerable, not 
infrequently 50,000 to 90,000 plants being destroyed in 
two or three weeks on a single nursery. 
Another species, Phytophthora parasitica, described — 
previously as a cause of “damping off” of seedlings, 
also produces foot rot. In this case the plant is attacked 
in much the same way as by Ph. cryptogea, but death is 
slower. Tomatoes planted out on March Ist may be 
destroyed by Ph. cryptogea up to the end of April, while 
it is not uncommon to find Ph. parasitica as the cause of 
death in June and July. 
The methods of controlling this disease are the same 
as recommended for ‘“‘ damping off”? due to these two 
species of Phytophthora. 
Botrytis Foot Rot.—Symptoms.—tThe first sign of this 
disease is the appearance of smooth, slightly sunken grey 
patches on the stem just about the soil level. These 
lesions enlarge, become dry and brown until finally they 
encircle the stem, when the top of the plant wilts and may 
fall over. Under moist conditions a grey fungal growth 
of Botrytis appears over the diseased area (Figs. 8 and 9). 
On cutting open the stem it can be seen that the fungus 
has penetrated the cortex, vascular system, and pith, and 
is travelling up the stem in the wood. The diseased 
tissues are dark reddish-brown in colour. " 
Causal Organism.—The cause of the disease is a 
species of Botrytis, which is one of the most common 
