The Effect of Modifying the Microenvironment Among Geranium Stock Plants Within a Greenhouse on Botrytis Blight and Sporulation of Botrytis Cinerea Progress Report — September 1992
Date 8/28/92
Title of Project The Effect of Modifying the Microenvironment Among Geranium Stock Plants
Within a Greenhouse on Botrytis Blight and Sporulation of Botrytis Cinerea
Institution where work is being conducted Michigan State University
Amount of Endowment Grant $25,000
Covering Period 1/1/92 to 12/31/92
Anticipated Date of Project Completion/Final Report 12/31/93
Individual(s) Conducting Project: Mary K. Hausbeck
(List Project Leader First)
Michigan State University – Title Visiting Assistant Prof.
Telephone Number (517) 355-4534
The Effect of Modifying the Microenvironment Among Geranium Stock Plants on Botrytis Blightand Sporulation of Botrytis Cinerea
Mary K. Hausbeck
Michigan State University
- A. Project Objectives:
- The primary objective addressed by this progressreport relates to the production of pathogen-free planting stock.
- B. Summary of Work Conducted:
- In the previous progress report it was demonstratedthat modifying the environment among stock plants using forced heated
air can negatively impact the occurrence of leaf blight among cuttings
taken from those stock plants. In that first study, an average of 74%
of the leaves became blighted due to Botrytis when cuttings were taken
from control plants grown in an environment that was not modified and
exposed to optimum conditions for disease development. In contrast,
only 26% of the leaves became blighted when cuttings were taken from
geranium stock plants exposed to forced heated air and treated in a
similar manner. Most recently upon further analysis, it was determined
based on the monitoring of environmental conditions, that prior to
removing the cuttings, the stock plants in the modified environment did
not experience leaf wetness whereas the plants in the environment that
was not modified experienced nearly 3 1/2 days of leaf wetness. These
wet conditions prior to the removal of cuttings from the stock plants
apparently resulted in conditions favorable for infection of the stock
plants by Botrytis and subsequent sporulation. Previous work conducted
in connection with this study showed that removal of cuttings from stock
plants in an environment that was not modified resulted in “spore
showers” providing inoculum for cuttings removed these plants. Once the
cuttings are placed in an appropriate environment for Botrytis
development (i.e. wet, high relative humidity) these spores germinate
resulting in leaf blight. This initial study has now been repeated
three times and the trend has been similar in that there was less leaf
blight in cuttings removed from stock plants grown in the modified
environment versus those grown in an environment that was not modified.
The amount of leaf blight occurring in the cuttings from plants grown in
the environment that was not modified varied according to the hours of
leaf wetness experienced by the stock plants just prior to harvest.
It is clear from these studies that environmental manipulation of the
stock plant growing area has significant implications for disease
management in the next step of the production chain which involves the
propagation greenhouse. This environmental manipulation reduces the
sporulation on the stock plants thereby reducing the inoculum that
occurs on the cuttings prior to their placement in the propagation house
which is wet and humid and conducive to Botrytis development. This
information will be helpful for all crops that are grown in a stock
plant and propagation misting system and is especially critical given
the continuing reports of resistance of Botrytis to commonly used
fungicides. Future plans include expanding these studies to further
understand the environmental parameters necessary for disease
development.
- C. Anticipated Benefits for Floral Industry:
- The environmental parametersnecessary to deter Botrytis blight will be formulated into a forecasting
system to provide growers with an economical disease management tool
that improves plant quality by reducing disease and pesticide sprays.
