Vergara - 1976 - Physiological and morphological adaptability of ri

EPIDEMIOLOGY OF SOUTHERN CORN LEAF BLIGHT 405
Dew was measured using Taylor dew meters located at l and 2m heights
within the cornlields.
Separate field studies evaluated the effects of leaf position and leaf age on
colonization and sporulation. Corn plants in the IO-leaf stage were inoculated
b_v atomizing a spore suspension over the entire plant. As soon as incipient infections
were visible, lesions on the third through the tenth leaf were selected
and marked. The size of each marked lesion was detennined daily and the data
were recorded separately for each leaf. After several days and at regular intervals
thereafter. the sporulation capacities of the lesions were determined by collecting
all spores separately from each lesion by a vacuum technique shortly after
the leaves were free of dew in late morning. The availability‘ of pertinent climatic
data enabled us also to correlate colonization rates and relative sporulation
with changes in climatic factors.
Briefly, the results demonstrated that colonization and sporulatitin were greatest
on the older. lower leaves and became significantly less at the intermediate
level, and on higher leaves. The fact that the major portion of inoculum is
produced on the lower leaves within the canopy of the field, and that much of
that inoculum is trapped within the canopy, probably accounts for our observation
that disease spread was largely from plant to adjacent plant rather than
from one point to another point at some distance. except during periods of
turbulence.
Modeling of disease
MODELING AND SIMULATION
cycle segments
With each process studied. an attempt xvas made to develop a model which
would predict the response of the particular process under cominotily encountered
levels and combinations of environmental parameters. In each case. the
problem was defined. the response to be measured was selected, and variables
which were thought to have a significant effect on the selected response were
chosen. Plots of the response (dependent) variable against various independent
variables were made and studied to help determine the general relationships
among the variables.
In most instances theoretical. linear. first order models of the fonn
Y — B0 + BIX]
were considered. where Y is the level of the dependent variable, X, . . . X" are
levels of the different independent variables, B‘, . . . . . . B" the parameters. and Fl
is the increment by which any individual Y may fall off the computed regression
line. The model was then tested using least squares linear multiple regression
analysis techniques to obtain estimates b" of B". Analysis was conducted using
the MINITAB and LIPREG regression analysis computer programs and processed
on an IBM model 360/‘70 digital computer located at The Pennsylvania
State University Computation Center.