358 
Journal of Agricultural Research 
Vol. XXVIII, No 4 
In fruits that have barely begun to enlarge after petal fall, all parts, receptacle, 
stamens, calyx, and even the peduncle, become dark brown over affected areas; 
the brown, at the edges, shades off into the natural green of the unaffected portion. 
Fruits mature enough to have turned red show over affected areas the same 
yellow to light brown at the center of the spot but with a transition from this 
through darker brown to purple to the natural red of the berry; ripe, fully colored 
fruits show sometimes no color change at all except a slight darkening of the 
red over affected spots, or sometimes a faint tinge of the purple which forms the 
transition to red on less mature fruits. 
On the market only the most advanced stages are seen. Here, however, the 
superficial growth of mold, rare in the field, is frequently seen and will serve as a 
diagnostic characteristic if taken in connection with the external color changes 
and the internal characteristics now to be described. 
In gross and longi-section (PL 1) strawberries attacked by Phytophthora show 
a marked browning of the vascular system accompanied usually by a less intense 
browning of all the other tissues.* In very early stages vascular browning is 
often the only visible symptom. So far as can be told by the eye or by touch, 
affected tissues are not disintegrated, though as mentioned earlier they are al¬ 
ways softened and decidedly tough and leathery. At no time is there any clear 
line of demarcation between diseased and healthy flesh nor can a separation of 
the two be made by mechanical means; it is not possible to lift or scoop out the 
lesion as can so easily be done with the lesions of Pezizella. 
HISTORICAL REVIEW 
This disease has been mentioned by the writer and his associates (18) in a 
preliminary report on field work. So far as can be learned that note and the 
present paper constitute the first record of Phytophthora as a parasite of straw¬ 
berries in the United States. Osterwalder ( 6) found a Phytophthora on straw¬ 
berries in Switzerland in 1912 which he identified as P. omnivora , apparently 
overlooking the fact that Schroeter (10 p. 235) in 1889 had adopted, instead of 
omnivora , the original specific name of cactorum , on the basis of the work of 
Lebert and Cohn (4) in 1870. The term omnivora had been used by de Bary in 
1881 (see Wilson (16 p. 75) to include all members of the genus Phytophthora 
which were not referable to infestans and became in time a “waste basket” into 
which was thrown any unidentified Phytophthora (16). Wilson also makes 
the further statement in commenting on this record by Osterwalder and on 
other records by Marchal (5) , Bubak (2) and Osterwalder (7) of the occurence of 
P. omnivora on other hosts, that “The figures and descriptions indicate that 
more than one species of Phytophthora may be concerned and that in all proba¬ 
bility none of these outbreaks were really due to the species which is credited 
with the damage.” (See also Lafferty and Pethybridge (3), footnote, p. 35.) 
CAUSAL ORGANISM: APPEARANCE IN CULTURE 
Pure cultures of the fungus were easily obtained from berries showing 
typical symptoms, by the following method: The berries were dipped twice 
in alcohol, the alcohol being burned off after each dipping; they were then cut 
across at the calyx end and the two halves were pulled apart with a flamed 
scalpel; portions of the infected “core” were then dug out from the torn surface 
with a freshly flamed scalpel and dropped into tubes of potato dextrose agar. 
More than 100 such plantings have been made, all but a very few of which gave 
the white, loosely matted growth characteristic of Phytophthora on this medium. 
The exceptions were either Botrytis or Pezizella. The fungus did not fill the 
tube though it occasionally grew up on the glass a centimeter or two above the 
surface of the agar slant. On oatmeal agar it usually made a scant, appressed 
growth, sometimes so scant that its presence could be told only by examination 
