CITRUS SCAB : ITS CAUSE AND CONTROL. 35 
are as severe as those occurring during the cool weather of spring or 
fall. 
Citrus scab is caused by a definite fungus usually but erroneously 
referred to as Cladosporium citri Massee. It has none of the charac- 
ters of Cladosporium Link. It has been confused with a common 
saprophyte in citrus lesions. 
The causal fungus does not live over winter on mature fruit. It 
passes this period on affected leaves which act as foci of infection the 
following spring . 
The citrus-scab fungus does not appear to be more virulent now 
than was the case a few years after its first introduction into America, 
nor are the various citrus varieties changing their former suscepti- 
bility. 
There is no material difference in percentage or degree of infection 
that could reasonably be attributed to immunizing or sensitizing in- 
fluences produced by the root stock on the scion. 
Cumulative evidence including spraying experiments and orchard 
observations, goes to show that citrus scab can be controlled satisfac- 
torily and economically. Scab in the nursery can be controlled 
readily by occasional applications of effective sprays. 
Plain Bordeaux mixture as well as Bordeaux mixture plus oil 
emulsion is very effective against citrus scab, either in the nursery or 
in the orchard. Burgundy mixture is distinctly less effective than 
Bordeaux mixture, and ammonical copper carbonate solution is much 
less so. 
Lime-sulphur solution is much less effective against this disease 
than is Bordeaux mixture. The other sulphur sprays are no more 
effective against citrus scab than is lime-sulphur solution. 
Spraying after the smallest fruits have attained a diameter of 
three-fourths of an inch has no effect on the control of scab. 
