Vergara - 1976 - Physiological and morphological adaptability of ri

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Climatic effects on the incidence of
plant diseases: the epidemiology of
southern corn leaf blight
R. R. Nelson
SUMMARY
he epidemiology of soutlieni corn leaf blight presented herein is illustrative
of research on climatic clTccts on incidence of plant diseases. The disease
cycle vras divided into discrete segments including spore release. spore deposition.
infection. colonization. and sporulation. and the etTect of pertinent climatic
parameters on their progress was determined under controlled environment conditions.
Field plot studies monitored the amount of disease and the rate of disease
increase initiated by simulated singlc and multiple-focus infections. Important
climatic factors were monitored. and the environmental data were unrelated
with disease incidence. Each segment of the disease cycle was modeled b)‘ regression
equations dcsigncd to predict thi: progression of the cycle undcr difTcring
environmental regimes. The disease model was synthesized and a simulation
prepared in FORTRAN 1V computer language. The validity of the simulator was
verified with field data.
INTRODUCTION
An understanding of thc effects of pertinent climatic factors on thc onset and
subsequent increase of plant diseases is essential to man's continuing efforts to
minimize disease losses. Research contributing to such an understanding is
epidemiological in nature zmd serves as the basis for an accurate prediction of
discasc dcvclopmcnt ovcr periods of time. ‘Nith such knowledge. and given the
current stage ofclimatic regimes that directly intlucncc discasc incrcasc. thc appropriate
and judicious use of available control incasurcs could bc cxcrciscd at
any timc.
The devastating and tvidesprezid epidemic of southcm corn leaf blight (SCLB)
in the [Jnitcd States in I9TU prompted an extensive research program on the
fipltltillllfllOg’ of the disease in the Department of Plant Pathology at the Pennsylvania
State University. The epidemic was incited by race T of Helniinthosporiiim
mqvdis Nisikado & Miyaki ivith an unprcccdcntcd virulence to Tcxas
male-sterile (Tins) com hybrids which occupied approximately 6U million acres
R. R. Nelson. Department of Plant Pathology. The Pennsylvania State Lliiiversity. University Park
Pennsylvania. USA.