Apr. 26,1924 Pecan Scab and Sources of Early Spring Infections 
329 
able defoliation, especially in nurseries, sometimes occurs. Severely infected trees 
usually shed their leaves earlier during the fall than they normally should. Occa¬ 
sionally the tender tips of the twigs are killed back from 5 to 15 cm. The greatest 
damage is done to the nuts which may become undersized, faulty, or rendered 
entirely worthless. 
An ascogenous stage of the pecan scab fungus is not known to exist. The 
fungus lives through the winter months in the form of more or less hemispherically 
shaped stromata situated in lesions upon the surface of twigs, rachises, petioles, 
and shucks. These stromata produce conidia the following spring. 
Hygienic measures tending to eliminate, as completely as possible, the various 
sources of the early spring infections, are very important as a means of keeping 
the disease within bounds so that spraying may be made effective. Twig lesions 
can be largely prevented by thorough summer spraying. The most practical 
method of disposing of the infected leaves and shucks after they fall to the 
ground is the thorough plowing under of these parts during late winter. If 
practicable to do so, the raking and burning of these affected parts would also be 
effective. 
Of the various available spray materials tried Bordeaux mixture was the most 
effective, although it sometimes causes serious injury to the foliage. 
Strong Bordeaux mixture and strong lime sulphur solution used as dormant 
sprays did not perceptibly reduce the amount of infection. 
The following are mentioned as instrumental in making effective control of 
pecan scab difficult: The large size of the pecan trees to be sprayed; the normal 
frequency of*summer rains prevailing in the southern pecan belt during June, 
July, and August; the long season of susceptibility of the pecan nut to scab 
infection; the close proximity of the young leaves to hold-over stromata on the 
twigs; and production of a second growth of leaves and twigs, subject to infec¬ 
tion if not protected by spfay. 
