324 
Journal of Agricultural Research 
Vol. XXVIII, No. 4 
of two factors: First a great number of infections directly causing the death of 
the nuts; and, second, infection of the pedicels, which are often so severely 
attacked that the flow of water and nutrient materials is partially or even com¬ 
pletely shut off. Frequently the pedicel is killed outright while the nut is yet 
partly green. 
ON THE TWIGS 
The twigs of certain varieties of the pecan, especially the variety Delmas, 
are very susceptible to scab. The terminal twigs on old, neglected Delmas 
trees are often killed back from 7 to 15 cm. in one season by the scab pathogen 
(PI. 2, A). The twigs of certain other pecan varieties, such as Alley, Van 
Deman, and Schley, are also susceptible but to a much lesser degree than those 
of the Delmas variety. Only the twigs of the current year’s growth are attacked 
by the scab fungus, and these are susceptible only while they are young, growing 
rapidly, and before lignification takes place. The scab spots on the twigs are 
olive in color, while the fungus is sporulating, but are black after the spores 
have been washed away. In size, the lesions range from 0.5 to 3 mm. in diameter 
(PI. 2, B and C). 
ON THE CATKINS AND DORMANT BUDS 
The writer has observed scab on pecan catkins only in a few instances. Appa¬ 
rently no injury is done to this floral part as the spots are few in number and have 
been seen only on the pedicels and bracts. The fungus does not seem to attack 
the pollen sacs. 
It is not unusual to find from one to three scab spots holding over from the 
previous seasons on a dormant bud. From sections made of such infected buds, 
the writer is led to believe that mycelium does not extend deeper than the outer 
bud scale. 
SOURCES OF PRIMARY INFECTIONS 
According to those who have made a thorough study of the apple scab fungus, 
the conidial stage of which greatly resembles Fusicladium effusum, the principle 
source of early spring infections is the ascogenous stage formed within the tissues 
of the fallen leaves of the previous season. The writer has frequently observed 
several forms of ascomycetous fungi on dead pecan leaves, twigs, and nuts, but 
none has been specifically connected with the pecan scab fungus. While an 
ascogenous stage, which one would expect to be a Venturia, may exist, it is as yet 
unknown. Many orchard and laboratory observations have led the writer to 
believe that even should Fusicladium effusum produce a perfect stage it would 
certainly be only a contributory factor in the perpetuation of the fungus, as in the 
South the conidial stage regularly lives overwinter in great abundance. 
TWIGS AS SOURCE OF PRIMARY INFECTIONS 
Under certain favorable conditions, the hyphae in scab lesions ont wigs remains 
alive during the mild winters of southern Georgia, and the following spring 
becomes very important sources of the early spring infection. The mycelium 
does not remain alive overwinter in all twig lesions. The scab spots formed 
during the early part of the season apparently are not able to live after the cortex 
of the twig reaches a certain stage of maturity. By the end of the summer, such 
early formed lesions become flattened and cracked and the fungus within appears 
to be dead (PI. 2, C and D). During the following spring many of them are 
either partially healed over or appear as black, sunken spots with slightly raised 
rings of cortical tissues surrounding them (PI. 2, E). In these older spots, 
resulting from early spring infections, the fungus seldom lives through the winter 
and they do not, therefore, appear to serve as sources of the primary infections. 
