394 OHIO EXPERIMENT STATION: BULLETIN 214 
Leaf-spot of cucumber is also due to fungi. (Phyllosticta Cucurbitacearum 
Sacc. and Cercospora Cucurbitae E.&E.) Of- the two species named, the 
Phyllosticta was the commoner in thrifty pickle fields in 1898; the Cercospora 
being apparently confined to wet fields, though this cannot be expected to hold 
true under all circumstances. The Phyllosticta was found almost exclusively 
upon the unsprayed pickle plants and seems, therefore, amenable to the same 
treatment as applied for downy mildew. (Bulletin 105). 
Mosaic Disease of greenhouse cucumbers has been recently studied in Ohio. 
This disease is analagous in character to the mosaic disease of tobacco and to- 
matoes and to the yellows of the peach. It is due to an oxidizing ferment in the 
leaves and is transmitted like the tobacco mosaic disease, by touching first dis- 
eased and then healthy plants. The fruitfulness of these variegated yellow 
plants is very low and it is best at all times upon the appearance of the disease 
to remove the diseased plants and destroy them. 
Nematodes or Eelworms (Hetervodera radicicola (Greef.) Mull.). These 
minute parasitic worms are often very destructive upon cucumbers under glass, 
They are especially soin some cases recorded in Bul- 
letin 73. The greatest injury may occur on the seedling 
plants, but plants of all ages ‘are destroyed by the para- 
sitic worms. Their presence may be known by the 
small, bead-like enlargements produced upon the roots 
or rootlets. This matter is treated at some length in that 
Bulletin. No remedy has been discovered that is effec- 
tive with plants once attacked by eelworms. The time 
to prevent this trouble is in the selection or preparation 
~ or treatment of the the soil for greenhouse benches. 
Indeed the nematodes seem to be present in old sod, and 
to some extent in decaying vegetable matter generally. 
An effective remedy against eelworms consists in steam- 
ing and so treating the soil that the parasites will be 
destroyed. For this procedure see calendar and Bul- 
letin 73. Also Massachsetts Exp. Sta. Bul. 55, In thus 
handling the soil due time must be given for draining 
and drying. 
Powdery Mildew (Erysiphe Cichoracearum DC.) of 
Fig. 49. Rootsofseed- cucumbers is also frequent in the forcing house, but 
ling cucumber with Nem- rarely destructive elsewhere. For this fungus a dilute 
ae na ed si copper sulfate solution is effective. See Bulletin 73. 
ee ae ones Root-Rot. The root-rot or so-called ‘‘leaf-curl’’ 
development on matured cucumber plants referred to 
Rhizoctonia, is often serious. It is more fully discussed under damping-off above. 
Spot of Cucumber Fruit or Cucumber Scab (Cladosporium cucumerium Ell. & 
Arth.), has been reported upon cucumbers by Dr. Arthur (Ind. Exp. Sta. Bul. 
19), and may prove injurious if prevalent. It should be found amenable to the 
same treatment recommended for anthracnose and downy mildew. 
Cucumber Wilts. The wilt diseases of cucumbers, likewise of other cucur- 
bits, are a source of usual complaint in the earlier season, as the plants are 
beginning to form vines. In 1899 these complaints continued much later. The 
plants suddenly wilt down as from lack of water, then soon die. What has been 
referred to the same general cause was also observed in the cucumber forcing- 
house, apparently starting in the leaves. Smith (Proc. Am. Ass. Adv. Sci. 1893) 
refers this disease to a bacterium (Bacillus tracheiphilue Smith) which is trans- 
_ ferred from diseased to healthy plants by the cucumber beetle and the squash 
bug. This form of wilt has been found on cucumbers, muskmelons and squashes 
