12 ClAIRANGASTAT OUNeS 


methods which are helpful, but do not expect to control Fusarium Branch Rot 
in this manner. Warm, moist conditions are favorable for the growth of the 
disease. Avoid excessive and overhead watering and injuries to plants. Provide 
plenty. of air, and run houses cool. Discard those varieties that are particularly 
susceptible. 
ALTERNARIA BLIGHT (Alternaria diantht) 
This disease is known as spot, blight or branch rot, Purple spots appear 
on leaves and flower parts, later browning and blighting the parts. Under moist 
conditions the blighted parts become overgrown with blackish or sooty masses 
of fungus. After benching, the fungus causes a prevalent branch rot centering 
at the nodes. Here the fungus causes dark colored spots or cankers which par- 
tially or completely girdle the branch. Ultimately the rot progresses deeper into 
the tissue, and the portion of the branch above wilts. The color of the invaded 
tissue is dark brown, almost black, and the color may extend from the bark to 
the wood. The discoloration extends inward from the outside, and does not fol- 
low the conductive tissue as does Fusarium. Infection takes place without the 
plant having first been injured, and almost always occurs in the field. Before 
branches wilt, the leaves are streaked or marked with whitish or light green areas. 
Certain varieties are more susceptible to the disease than others. Inside culture 
will usually eliminate Alternaria. Spraying with Bordeaux weekly from the time 
that plants go to the field until they are benched will form a chemical barrier 
between the plant and the fungus which is very effective. Alternaria 1s not carried 
in the cuttings, and any variety is likely to be attacked. 
BACTERIAL LEAF SPOT (Phytomonas Woodsu) 
This disease is so rare in many sections that growers are likely to confuse it 
with alternaria blight or fairy ring, and therein lies its greatest danger. It is a 
foliage disease caused by a bacteria or microbe which progresses from the lower 
leaves upward, attacking the stem and bud only in very severe cases. If not 
checked, the plant becomes defoliated and will die. In any case, the plants will be 
checked and production arrested. The disease occurs only in the presence of 
injuries, but spiders, thrips, aphids, etc., will provide sufficient injury for the bac- 
teria to gain entrance. It is, therefore, of vital importance that plants be kept 
free of insects. The development of the disease is slow at temperatures of 60 
degrees or less, and very rapid at higher temperatures. The trouble is first indi- 
cated by the presence of small, oval spots of pale brown color. These spots are 
usually sunken, and soon become yellow with a dark green or purple margin. 
These spots may include the entire breadth of the leaf, and where spots are num- 
erous, they have a tendency to grow together. Several spots ultimately cause the 
death of the leaf, in which case the leaf turns a yellow straw color, withers and 
dies, the spots retaining a rusty brown color. Greenhouses should be kept cool, dry 
and well ventilated. There must be no overhead watering of any kind. Fortu- 
nately the disease may be cured or prevented by use of a spray consisting of 
3 pounds of zinc sulfate, 1! pounds alum, 4 pounds hydrated lime, and a good 
spreader to 50 gallons of water. Dusting with fine sulphur is a further pre- 
caution which may be taken. 
RUST ... (Uromyces caryophyllinus) 
Sulphur is the most effective preventative and cure for rust. Use a fine dust- 
ing sulphur, and apply it with a good blower. Use it on young plants as soon 
as the first trace of rust appears, and apply on bright, warm, days. Sulphur 
may safely be used once a week or oftener. In light soils it may cause a slight 
acid reaction, but this is easily overcome. In the field where dusting is imprac- 
tical, lime-sulfur may be sprayed. Bordeaux or other copper sprays have very 
little effect on rust. The disease is so easily prevented or cleaned up that there 
is no excuse for a grower permitting his plants to become damaged by it. Keep 
plants dry, provide plenty of air, and run houses cool. 


