May 17,1924 
Rots of Strawberries 
647 
in connection with this disease found that the hyphae penetrate the cell walls 
readily and dissolve the middle lamellae. The hyphae were found to grow be¬ 
tween the cells for some distance, then to penetrate the cell walls becoming 
intracellular. All parts of the berry are subject to attack by the fungus, which if 
allowed to develop does not stop at localized infections. It is evident from the 
way the cytoplasm shrinks away from the cell walls and becomes disorganized 
that the host cells are killed quickly. Water is so slowly and gradually with¬ 
drawn from the host cells that it evaporates from the surface of the berry and 
no leak is caused, in spite of the fact that hyphae penetrate pulp or storage 
cells everywhere. The rotting berry thus becomes dried and mummified. 
COMPARISON OF THE FOUR BROWN ROTS 
The two field rots most likely to be confused with the hard brown rot are those 
caused by Botrytis and Pezizella, although each has sufficiently distinctive 
characters to make indentification reasonably certain. The Botrytis rot is a 
lighter brown and more watery at the beginning. That caused by Pezizella 
forms a pocket in the sticky scablike rotted portion. In only one case out of 
126 cultures made by direct transfer of pulp from berries selected in the field 
as affected with hard brown rot was Botrytis obtained as a result of faulty 
diagnosis. The hard rot caused by the Rhizoctonia under discussion in this 
paper is easily distinguished from the tough dry rot due to Botrytis by the clear 
line of demarcation between healthy and diseased tissue characteristic of the 
Rhizoctonia rot. 
The Rhizoctonia hard brown rot and the Pezizella soft brown rot are alike 
in that in both there is a distinct line separating the diseased from the healthy 
tissue. Not infrequently berries infected with the Rhizoctonia when shipped 
arrive at destination with the uninfected portion of the berry still edible. A 
berry infected with Botrytis or Phytophthora when shipped is usally so rotten 
as to be wholly inedible on arrival. The leather rot (Phytophthora rot) is 
the only one of the four brown rots to cause a marked vascular discoloration. 
The surface of berries affected with Phytophthora under moist conditions 
becomes covered with a pure white growth of hyphae and conidiophores (PI. 1, J). 
Those affected with Botrytis develop the gray mold which consists in part of 
branched conidiophores. The Pezizella rot develops little disc-shaped fruiting 
bodies sometimes called sporodochia. The Rhizoctonia hard rot develops only 
light brown, fluffy hyphae. 
The mycelium of Botrytis penetrates the host cells in every direction and is 
both inter- and intracellular. The hyphae of the hard brown rot fungus are 
typically intercellular, but they are often found within the cells. Hyphae of 
the Pezizella are probably capable of penetrating the walls of the pulp cells 
but are not known to penetrate the cutinized epidermis. Little is known as to 
the manner in which the hyphae of the leather rot attack the host cell. 
KNOWN DISTRIBUTION OF THE VARIOUS BROWN ROTS 
The Rhizoctonia rot is now known from central Florida, North Carolina and 
possibly from Tennessee. Leather rot has been found in Mississippi, Louisiana, 
Arkansas, Tennessee, Missouri, Kentucky, and Illinois. Pezizella rot has been 
observed by the writers in Cuba, Louisiana, Florida, Arkansas, Virginia, Mary¬ 
land, Wisconsin, and Alaska. Botrytis has been found to some extent as a fruit 
rot of strawberries in every strawberry region visited, though it varies greatly 
in abundance. 8 It is serious in Alaska 9 and during many seasons in New England, 
and may become abundant in more southern regions during wet weather. Botry¬ 
tis is also known to cause rot of strawberries in England. 
8 Stevens, Neil E. rots of early strawberries in Florida and southern California. Amer. 
Jour. Bot., 9: 204-211. 1922. Literature cited, p. 211. 
9 Anderson, J. P., Botrytis cinerea in alaska. Phytopathology. 14: 152-155. 1924. 
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