ALE Cem oN DEHS ON, UNC., CHICAGO 
Treatment of Insects and Diseases 
RHIZOCTONIA STEM ROT. Foilage becomes dull, losing green color; entire plant wilts suddenly. 
Stem near soil wet and soft; the shredded bark sloughing off from the slightest twist, exposing 
harder tissues beneath. Roots remain intact. Brown knots of fungus mold evident about decayed 
portion of stem and adhering soil. Is caused by a common mold fungus which inhabits most 
soil and soil contaminated sand. It is not carried in cuttings. Ordinarily the mold is a harmless 
soil fungus, but under favorable conditions it becomes a serious disease. It thrives under exces- 
sively moist and warm conditions. Control is a matter of correct watering and airing, sanitation, 
shallow planting, soil sterilization and soil rotation. Spraying is useless. Steam sterilization, or 
sterilization with tear gas, helps, but sterilized soil may easily become reinfected if plants are 
brought in from outside. 
FUSARIUM BRANCH ROT. Begins with the wilting of a single branch. Leaves are a dull green, 
then yellow and straw colored. The affected branch dries and shrivels. Infection at first is 
localized in the stem or branch near crotches or nodes. Injuries of one sort or another caused 
by careless handling, too rapid growth, topping, picking, etc., are essential for infection except 
where the disease has been carried with the cuttings. Upon cutting the branches lengthwise, 
the conductive tissue under the bark is seen to be yellowish or reddish brown up and down 
following the sap channel. If the branch is removed before the disease has progressed into 
the stem, the plant may possibly be saved. Later the brown color expands into the inner tissue 
of the stem and into the outer bark from the conductive tissue. When the stem is invaded, the 
branches on the infected side die, and ultimately the entire plant succumbs. The inside tissue 
of an invaded stem is dry and of a dull brown color, similar in appearance to dead timber. 
As the infection is usually aerial, soil sterilization is of little value, and there is no known 
spray which will prevent or cure it. Sterilizing benches, flats, soil and sand are sanitary 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, 
ALTERNARIA BLIGHT. 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 col- 
ored spots or cankers which partially 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 follow 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 is not carried in the cuttings, and 
any variety is likely to be attacked. 
BACTERIAL LEAF SPOT. 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. The 
disease occurs only in the presence of injuries, but spiders, thrips, aphids, etc., will provide 
sufficient injury for the bacteria 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. Greenhouses should be kept cool, dry and 
well ventilated. There must be no overhead watering of any kind. Fortunately 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 precaution which may be taken. 
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