- Phyllopane microorganisms on the leaf surfaces of bean
(Phaseolus vulgaris L. ), hop (Humulus lupulus L. 'Fuggle-H'),
mint (Mentha piperita L. 'Mitcham') and tomato (Lycopersicon
esculentum Mill. ) has been observed by cultural methods. A leaf
impression method was used to examine both actively growing and
inactive propagules present on the surfaces of the leaves. A surface
sterilization method was also used to detect the presence of any fungi
occurring inside the living tissues. All leaf samples were collected
from different locations in the Willamette Valley, i. e. , Benton, Lane,
Linn, Marion, Polk, Washington and Yamhill Counties. A total of
38 species of microorganisms were found on the surface of healthy
leaves of all four host plants. They are divided into five categories
which are as follows. First, several microorganisms are very commonly found on
the leaf surfaces of all plants and at almost every location; with
frequencies of occurrence from 0.01-97 percent. There are 16
species in this first category and examples are Alternaria tenuis
Nees ex Per. , Aureobasidium pullulans (de Bary) Arn. , Cladosporium
cladosporioides (Fres. ) de Vries, C. herbarum Pers. ex Fr.,
Epicoccum purpurascens Ehrenb. ex Schlecht., Sporobolomyces
roseus Kluy. & van Niel, and so forth.
Second, microorganisms which occurred mainly on bean, mint
and tomato leaf surfaces, with the range of frequencies between 0. 01-
29 percent. Thirteen species were isolated, e. g. Acremoniella atra
(Corda) Sacc. , Aspergillus niger Tiegh. , Fusarium oxysporum
Schlecht. , and Phoma sp. etc.
Third, microorganisms which grow mainly on tomato leaves
with some occurrence on mint or bean leaves.
Fourth, microorganisms which grow on tomato and mint leaves
only. The frequency of occurrence was between 0.01-29 percent.
Fifth, other epiphyllous microorganisms besides fungi, include
species of actinomycetes and bacteria that were not identified. These
microorganisms, especially the bacteria, abounded on all of the crop
leaves and at every location.
Numbers of the internal fungi were found in lesser numbers
than those on the leaf surfaces. Seven species were isolated from inside of the healthy leaf tissues of the same crops. They were
Alternaria tenuis, Cladosporium cladosporioides, Epicoccum purpurascens,
Phoma sp. , Stemphylium botryosum Wallr. , Ulocladium
atrum Preuss, and Verticilium sp. A. tenuis was the most commonly
present at the cut edges of bean leaf squares with average
57 percent. The rest of them were varied, and ranged from 1-17