26 BULLETIN 45, HAWAII EXPERIMENT STATION. 
fungus travels inward, past the woody bundles and across the entire shoot, 
which then falls over as if broken at the base. Even before this collapse takes 
place the disease will have penetrated beyond the woody vascular tissue into 
the soft and watery core, in which it travels upward and downward with great 
rapidity. The core tissue is quickly discolored and soon decays, leaving the 
woody circle of vascular tissue like a hollow skeleton of the original shoot. 
During moist weather conditions, a white mycelial growth may be seen over 
the affected tissue and in the hollow stem, and white mycelial strands may 
occur in the soil surrounding the plant. This mycelium soon produces small 
white tufts, which become round, smooth, and hard, and change from white to 
yellow, then finally to dark brown. Such hardened mycelial masses are known 
as sclerotia. They are the only reliable means of identifying the disease. 
When mature and dry they resemble mustard seed both in size and color. 
During dry weather these sclerotia do not develop under natural conditions, 
and artificial means may be adopted to induce their formation in order to 
diagnose the disease. This can be done by placing one of the affected shoots 
in a moist chamber * * *. 
Larsen records alfalfa, coreopsis, taro, and Irish potato as affected 
with sclerotium in these islands. 
Control. — Rolfs 1 found the Sclerotium disease of tomatoes sus- 
ceptible of treatment with some soluble form of fungicide such as 
an ammoniacal solution of copper carbonate or eau celeste. He 
writes as follows regarding this means of treatment, which is very 
successful in Florida: 
One of these fungicides, preferably the ammoniacal solution of copper car- 
bonate, should be sprayed on the soil about the stem of the plant. By spraying 
on a half teacupful at this point the plant is usually perfectly protected against 
infection. In using this remedy it should be remembered that where the 
fungus has gained entrance into the tissues of a plant before the fungicide 
has been applied, the remedy will be of no avail. 
The formula and description of preparation of the two fungicide 
solutions is given on pages 13 and 11. As an additional means of 
controlling the ravages of the fungus, the soil about the plants should 
be loosened and exposed to the action of the sun and air. In dry 
weather this serves to kill the fungus to some extent, thus preventing 
infection. 
Common or Cokky Scab {Actinomyces chromogenus). 
The disease known as common or corky scab attacks the growing 
tubers at any stage of development (figs. 1 A and 2 B). The centers 
of infection are first evident as small brownish spots on the sur- 
face of the tuber. The spots increase rapidly in size and depth 
until the whole surface may become covered with the unsightly, 
rough, scabby areas. In some cases the potatoes crack open or the 
spots are enlarged and deepened by insects. The scabs consist of 
accumulated corky tissue formed by the tuber in an attempt to pro- 
tect the underlying tender tissues from the irritating action of the 
i Rolfs, P. H. Tomato diseases. Florida Sta. Bui. 117 (1913), p. 41. 
