June, 1955 
cies of insects in hastening the decline of 
mats in nature was followed closely. 
Weather Data 
An attempt was made to relate average 
monthly temperatures and precipitation 
with conidial sporulation, perithecium 
formation, viability of spores, and general 
mat deterioration. Weather data were 
obtained from records of the United 
Curt: Oak Witt INocuLA 
285 
ner. A water suspension of conidia was 
prepared from a 7-day-old culture of En- 
doconidiophora fagacearum and adjusted 
to approximately 300,000 spores per ml. 
Circles were made with a wax pencil on 
the outside bottoms of Petri dishes con- 
taining 2 per cent water agar. One drop 
of suspension was placed on the surface 
of the agar within each circle, and each 
of the dishes was subjected to one of the 
Table 2.—Germination of conidia of Endoconidiophora fagacearum at various centigrade 
temperatures on 2 per cent water agar. 
Per Cent GERMINATION AT DESIGNATED TEMPERATURE 
NuMBER 
or Hours | 
iE 16° 25S 28° Sie 34° 36° 
“2 eee 0 0 3) 37 9 2. 0 
Li) ae 0 2 19 83 73 16 0 
ic» th Sie 0 6 48 93 86 25 0 
eerie ss ee 0 11 65 94 91 29 0 
GU a age a 0 12 74 96 92 35 0 
States Department of Commerce Weather 
Bureau for stations nearest the areas be- 
ing studied. None of the study areas was 
more than 12 miles distant from the near- 
est weather station. It is realized that 
temperature and precipitation may vary 
to some extent within even this short dis- 
tance, but it was not feasible to install 
expensive, unguarded weather-recording 
equipment in the wilt areas. 
LABORATORY STUDIES 
Spore Germination 
The germination of conidia of Endo- 
conidiophora fagacearum by other work- 
ers has already been reviewed. For these 
conidia, solid agar of a low dextrose con- 
tent and malt solutions have been shown 
to be good germination media at 25 to 30 
degrees C.* However, in the present 
studies, a medium and a_ temperature 
were desired that would insure a high 
percentage of germination, but that, at 
the same time, would tend to discourage 
growth of contaminating fungi and re- 
tard the production of secondary endo- 
conidia. 
The germinability of laboratory-grown 
conidia was tested in the following man- 
* All temperatures given in this report, unless other- 
wise labeled, are degrees centigrade. 
following incubation temperatures: 7, 16, 
25, 28, 31, 34, and 36 degrees at 12-hour 
intervals for 60 hours. Four hundred 
spores were counted for each test temper- 
ature, and a record was made of the num- 
ber of spores germinated. Spores were con- 
sidered germinated if the germ tubes were 
about the same length as the spores. 
The highest germination rate was 96 
per cent at 28 degrees; no germination 
occurred at 7 degrees nor at 36 degrees 
during the 60-hour period, table 2. The 
upper limit of the germination range ap- 
peared to be 34 degrees, fig. 4; at that 
temperature, 35 per cent germination oc- 
curred, but the germ tubes did not con- 
tinue to grow. Secondary sporulation ap- 
peared to be most abundant at 16 and at 
25 degrees. 
The germinability of conidia taken 
from naturally occurring mycelial mats 
was determined at 25 and at 28 degrees. 
Some of the spores were germinated on 
agar containing 2 per cent of dextrose and 
some on 2 per cent water agar. Most 
spore suspensions made from naturally 
occurring mats contained, in addition to 
conidia of Endoconidiophora fagacearum, 
spores and hyphal fragments of several 
other fungi, particularly species of Peni- 
cillium, Trichoderma, and Graphium. 
Drops of the suspension were placed on 
