DISEASES OF CULTIVATED PLANTS 449 
forms and the normal leaves. Recent investigations by Westerdijk show the 
disease to be distinct from the mosaic disease of tobacco though doubtless ana- 
logous; the modified leaf forms were obtained by artificial inoculations both by 
Westerdijk and in the Pathologium of this Station by Manns. 
Nematodes may be very injurious to tomatoes grown under glass. They 
cause, as on cucumber plants attacked, gall-like enlargements on the small 
roots of the tomato. Previous soil treatment to destroy the nematodes is the 
remedy in this instance, as in the other. It will usually occur that tomato 
plants are less susceptible to injury by nematodes than are cucumbers and 
melons. 
Point Rot of green tomatoes, especially in the forcing-house, is often the 
most serious trouble with which the tomato grower under glass has to contend. 
It was stated in Bulletin 73 that this trouble was observed to be most destructive 
in cases of scant water supply in ‘the soil. This observation was again 
confirmed by the Horticultural Department of the Station during the season 
of 1899. The trouble was checked by abundant and careful watering, even 
when it had been very bad, and was again produced by withholding water and 
allowing the plants to dry out. The cause appears to be largely due to 
conditions of drouth, and while other causes than the one just stated, notably a 
certain bacterium does join to produce point rot, none other appears so under 
control as water conditions. The remedy lies of course, in the avoidance of 
drouth from which the rot may indirectly result. 
Root-Rot or Rosette occurs frequently in 
greenhouses where tomatoes are grown fol- 
lowing crops of lettuce. The fungus produces 
various effects which are commonly damping 
off of the younger seedlings or collapse of the 
older ones; recently a basal constriction of the 
stem of mature plants is traced to Rhizoctonia. 
In this case wilting of plants resulted. It 
seems to be propagated under greenhouse 
conditions where much organic matter is used 
and calls for soil disinfection through steaming 
or formalin drench as described elsewhere 
under letiuce and under soil diseases. In 
older plants the symptoms are _ shortened 
development of the axis giving effects similar to 
that in lettuce. . Fig. 98. Stems of young green- 
Sclerotium Blight. This is a wilt disease house tomato plantsdamped off from 
first reported by Rolfs from Florida but it is ttacks of “Rhizoctonia.” From a 
now present in Ohio greenhouses. The first a dail ca 
symptom is wilting of terminal portion of plant. The dead plants and dis- 
eased portions shows in them sclerotia of the fungus which causes the trouble. 
These are of the size of mustard seed or smaller, at first milk white and finally 
mahogony red to black. Sometimes these schlerotia grow together in anvil- 
shaped masses. Burning diseased plants is advised. 
Wilt. A wilt (Fusarium sp) of tomatoes in addition to that described under 
bacterial disease has been discovered recently in greenhouses in Ohio as well as 
otker states. It is due to a Fusarium. 
