The Effect of Modifying the Microenvironment Among Geranium Stock Plants Within a Greenhouse on Botrytis Blight and Sporulation of Botrytis Cinerea 1993 Proposal
GERANIUM STOCK PLANTS WITHIN A GREENHOUSE ON BOTRYTIS BLIGHT AND SPORULATION
OF BOTRYTIS CINEREA
INTRODUCTION - Tetraploid (2N=36) and selected cultivars of diploid (2N=18)
geraniums
(Pelargonium x hortorum L.H. Bailey) are propagated asexually by cuttings.
Stem blight caused
by Botrytis cinerea Pers. ex. Fr. typically begins in the broken or
cut-off stem surface of the stock
plant and progresses downward, causing a dieback of the entire stem
and in severe cases extends
into the base of the plant resulting in death (Nichols and Nelson,
1982). Observations suggest that
stem blight is a limiting factor in production.
Stock plants are pinched at regular time intervals or treated with the
growth regulator
ethephon (Florel; 2-chloroethyl phosphonic acid) (Tjia and Kim, 1975)
to increase plant branching
and the number of growing points that can be removed as cuttings. This
management practice
produces low, compact plants with dense canopies that limit light and
air penetration and promote
senescence of the lower leaves (Rogers, 1982). Close spacing of stock
plants to maximize cutting
production greatly enhances these conditions. Under specific environmental
conditions, Botrytis
readily infects these senescent leaves and sporulates, providing ample
inoculum to infect stems
wounded during the harvest of cuttings.
Traditional methods of controlling stem blight include fungicide application
and sanitation.
However, fungicide efficacy may be limited by a dense stock plant canopy
shielding senescent,
sporulating stems and leaves from adequate fungicide coverage. Observations
from a commercial
greenhouse indicated that atmospheric conidial concentrations continued
to increase following
calendar applications of chlorothalonil and iprodione to geranium stock
plants. Also, the
occurrence of fungicide resistance remains a constant threat (Dennis
and Davis, 1979; Katan, 1982;
Maude, 1980; Northover and Matteoni, 1986).
Sanitation measures typically include the removal and destruction of
diseased plant
material. Dead leaves at the base of plants and organic matter in and
under benches may support
Botrytis growth. Melchers (1926) isolated Botrytis (considered to be
B. cinerea Pers.) from organic
matter in and on the sand of cutting benches, moist soils and elsewhere,
that may have potentially
served as a source of inoculum. However, maintaining the high standard
of hygiene necessary to
reduce inoculum sources is time-consuming and costly for commercial
geranium growers. The
benefit of such sanitation efforts has been questioned by Plaut and
Berger (1981) who concluded
from studies of B. cinerea on begonia that sanitation measures may
be less effective that previously
theorized. Low initial disease was apparently compensated for by an
accelerated rate of disease
development. Cultural methods of controlling diseases caused by B.
cinerea have not been
thoroughly investigated. Heursel and Kamoen showed that lignified (”hard”)
cuttings of
Rhododendron spp. can be better stored without loss due to B. cinerea
than ’soft’ cuttings.
Similarly, Cline and Neely showed that when wounded geranium cuttings
were allowed to “heal”
prior to inoculation with Pythium ultimum, disease incidence and severity
decreased.
Controlling disease caused by B. cinerea through modification of the
greenhouse
environment is an attractive addition to traditional control methods.
Environmental modification
to control disease caused by B. cinerea is typically aimed at enhancing
air circulation and
minimizing the duration of free moisture on the plants (Rogers, 1982).
B. cinerea is dependent on
a water film for conidial germination and infection, therefore, preventing
temperatures from
reaching the dew point is an effective mechanism of disease escape
(Jarvis, 1989). Although event-
driven, interactive computers are available with the capacity for predicting
disease epidemics and
altering the greenhouse environment, the data base necessary for the
development of software that
will provide predictions with a high confidence level is lacking.
BACKGROUND INFORMATION - The following results were used as a basis
for the proposed
research: Combinations of plastic mulch and intervals of forced heated
air were incorporated
among geranium (Pelargonium x hortorum) stock plants within a research
greenhouse. According
to the data, forced heated air among stock plants was effective in
reducing the incidence of
sporulating B. cinerea on necrotic leaves in comparison to the plastic
mulch treatment and the
controls.
Continuous, forced heated air applied from beneath an open-bottom bench
by an electric
heater, fan, and poly tube incorporated among geranium stock plants
within a commercial
greenhouse significantly reduced the incidence of stem blight, and
the incidence of sporulating B.
cinerea on blighted stems and necrotic leaves in comparison to the
control. During days when
grower activity was documented, B. cinerea conidial concentrations
estimated using a Burkard
recording spore trap within the modified area were lower than the concentrations
trapped within
the control area.
Another study used in preparing this research proposal showed that a
minimum of 24 hr
in an environment of low RH between stem wounding and subsequent inoculation
and incubation
in a dew chamber was necessary to significantly limit stem blight incidence.
When inoculated
plants were placed in an environment of low RH for a minimum of 24
hr prior to incubation in a
dew chamber, stem blight incidence was significantly limited. The longer
inoculated plants were
maintained in an environment of low RH prior to incubation in a dew
chamber, the lower the stem
blight incidence.
Results from studies conducted thus far within years 1 and 2 of this
proposal under
objective 1 were also used in preparing this research proposal: The
objectives were to determine
the effect of length of dew period at various temperatures on conidial
germination and subsequent
infection and lesion production on geranium leaves and wounded geranium
stems exposed to a
standardized number of conidia under controlled environmental conditions,
with the conidia applied
in a dry state similar to that occurring in nature; and to determine
the effect of extended dew
duration on postinfection hyphal development within lesions.
An isolate of B. cinerea, originally isolated from Michigan-grown geraniums
was used in all
experiments because it was highly virulent and it sporulated prolifically
on artificial media. The
fungus was grown on potato dextrose agar (PDA) for 12-16 days at room
temperature and under
a 16 hour fluorescent light photoperiod. A galvanized sheet metal cylinder
(10″ in diameter by 20″
deep) was used as a settling tower. Conidia were collected from sporulating
cultures using a
pasteur pipet connected to a water aspirator. At very low suction,
conidia were collected in the
pipet without being sucked into the aspirator. Conidia were tapped
out of the pipet onto weighing
paper. Inoculum was quantified by weight. Amounts of conidia weighing
1, 2, 3, 4, 5, 6, 7, 8, 9, and
10 mg were used as inoculum and determined with a hemacytometer to
represent approximately 2.8
x and 49.0 x 10 6 condia for weights of 1 and 10 mg conidia, respectively.
Over this range, each 1
mg of inoculum contained approximately 5.1 x 10^6 conidia.
For inoculation, leaf discs placed on moist filter paper within petri
dishes were positioned
within the settling tower and dry conidia were dispersed near the top
of the chamber by directing
a low velocity stream of air from a pipet tip over the conidia on a
piece of weighing paper. A cover
was positioned over the top of the cylinder to reduce air currents
and allow the conidia to settle on
the leaf discs.
On wet geranium leaf discs, conidia of B. cinerea began to germinate
within 60 minutes of
inoculation at the optimum temperature of 20′C. Four hours after inoculation,
40% of the conidia
had germinated and by 6 hours 77% of the conidia had germinated.
Cuttings were excised from stock plants 2 cm above a plant node using
name sterilized razor
blades. Dry B. cinerea conidia were used as inoculum. Dry conidia were
dusted onto the cut
surface with a camel’s hair brush. Control and inoculated plants were
immediately placed into a
darkened, commercial dew chamber at 15, 20, and 25′C. The prepared
stubs were examined with
an ISI-60 scanning electron microscope (International Scientific Instruments,
Holland, NY). In
addition, a stem from each treatment time was transversely cut 5 mm
from the inoculted surface
and then cut longitudinally in half.
Germination of the conidia on the wounded surface of the stem occurred
within 60 minutes
of inoculation at temperatures ranging from 15 to 25′C. After 3 hours
of leaf wetness, 48%,48%,
and 41% of the conidia had germinated when exposed to temperatures
of 15, 20, or 25′C,
respectively. At 15 and 20′C, maximum germination (68%) occurred after
9 hours of leaf wetness.
In contrast, at 25′C only 55% of the conidia germinated after 9 hours
of leaf wetness with maximum
germination (73%) occurring after 12 hours of leaf wetness. Enzymatic
degradation at the point
of penetration of the germ tube was observed. At 15′C, germ tube elongation
occurred most rapidly
between 3 hr (4.0 mm) and 6 hr (14.3 mm). At 20′C, germ tube elongation
occurred most rapidly
between 6 hr (5.5 mm) and 9 hr (11.0 mm). In contrast, at 25′C, germ
tube elongation occurred
most rapidly between 9 hr (7.0 mm) and 12 hr (20.9 mm). Germ tubes
were observed to have
ramified the cut surface of the stem within 6 hours after inoculation.
Cross sections showed that
by 12 hours hyphae were observed within the xylem vessels and had penetrated
through the cell
walls. However, the lesions indicative of stem blight were not observed
until 24 hours following
inoculation.
Results from studies conducted thus far within years 1 and 2 of this
proposal under
objective 2 were also used in preparing this research proposal: The
objective was to utilize the
information gathered to construct computerized software to regulate
the level and duration of
temperature and relative humidity necessary to interrupt the disease
cycle of B. cinerea. Previous
data showed that forced heated air among stock plants could significantly
decrease the infection of
lower leaves of the plants and subsequent infection of wounded stems.
Previously, it was unknown
if this benefit could be realized further in the production chain.
Recently conducted studies demonstrate that modifying the environment
(reducing hours
of leaf wetness and relative humidity) among stock plants using forced
heated air applied from
below a bench with a top that facilitates air movement can negatively
impact the occurrence of leaf
blight among cuttings taken from those stock plants. In our first study,
when 60 cuttings were
taken from control plants grown in an environment that was modified
and exposed to optimum
conditions for disease development, leaf blight was reduced by 39%
in comparison to cuttings taken
from control plants grown in an environment that was not modified.
When the experiment was
repeated, similar results were observed with leaf blight on cuttings
removed from stock plants grown
in a modified environment reduced by 38% in comparison to cuttings
taken from control plants
grown in an environment that was not modified. When the experiment
was run a third and fourth
time, disease was decreased by 27% and 19%, respectively.
These experiments clearly show that environmental modification will
not only reduce B.
cinerea among stock plants, thereby reducing stem blight and increasing
cutting production, but
that the leaf blight on the cuttings removed from these stock plants
will also be limited.
REVIEW OF SIGNIFICANT LITERATURE - Botrytis blossom blight and leaf
spot caused by B.
cinerea Pers. ex. Fr. was first reported on geranium by Melchers in
1918 with complete symptom
description following in 1926 (Melchers). Annual dollar losses in geranium
production nationwide
due to B. cinerea are estimated at $5.1 to 7.6 million based on known
figures. Losses in
Pennsylvania alone are estimated at $130,000 to $190,000 (personal
communication; Oglevee
Limited). These estimates do not include the costs of B. cinerea infection
resulting in reduced plant
quality or decreased cutting production.
Nichols and Nelson (1982) reported that Botrytis typically lives on
aging tissue such as
flowers, leaves, broken stems, and cutting stubs, but under appropriate
conditions can severely
damage leaves, flowers, and stems of healthy plants, especially if
the tissue is succulent. Leaf
lesions on geraniums commonly develop where infected senescent flower
parts have fallen. These
lesions enlarge if sufficient moisture is present, becoming irregular
in outline and potentially
infecting the entire leaf (Melchers, 1926).
Conidia may be a phylloplane resident resulting in latent infection
under desirable
conditions. Conidia are considered the primary source of infection
of cutting stubs and a latent rot
infection of cuttings. Nichols and Nelson (1982) suggested conidia
can become lodged on the stern
surface remaining dormant until cuttings are placed in the propagation
bench for rooting. Under
these wet and humid conditions, the conidia germinate forming a cutting
rot. Spraying
chrysanthemum stock plants with fungicide decreased subsequent infection
on detached cuttings,
suggesting stock plants were an important inoculum source (Smith, 1967).
Moisture and temperature are of primary importance for B. cinerea conidia
germination and
subsequent infection, although Good and Zathureczky (1967) found that
conidia were very tolerant
of drying. Melchers (1918) suggested in his original description of
B. cinerea on geranium that an
abundance of moisture and insufficient ventilation favored this disease.
Similarly, leaf and flower
blight were observed on geranium in glasshouses and in shelted places
oudoors in southern
California, especially during rainy weather (Baker, 1946). Loosses
of greenhouse tomatoes and
cucumbers were estimated at 60 to 75% during a season of damp, cloudy
weather due to Botrytis
stem and fruit rots and blossom blight which were generally considered
of minor importance
(Kadow, et al., 1983).
Lesion growth on geraniums was reported to increase with temperatures
from 10 to 25′C.
At 30′C, typical Botrytis lesions and sporulation on geraniums did
not occur (Hyre, 1972).
DeLozier (1980) showed sporulation to be greatest at 15 to 20′C with
100% RH. At 100% RH,
temperatures of the range 10 to 30′C had no significant effect on the
number of plants infected, the
latent period, or the rate of lesion growth. Similarly, the rate at
which artichoke bracts decay
following inoculation increased with temperatures from 0 to 20′C, although
the increase was not
uniform (Upton and Harvey, 1960). Heavy B. cinerea infection of statice
flowers, bracts, and scape
wings occurred at 24′C with moderate infection at 20 and 28′C (Jackson,
1960). The optimum
temperature for the leaf-spotting phase of gladiolus was approximately
55 to 65′F with slightly less
infection at 40 to 45′F (McClellan et al., 1949). Conversely, poinsettias
grown at continuous 10′C
showed a significant increase in incidence of B. cinerea in comparison
to plants grown at 17′C
continuous temperature (Sammons et al., 1982). Similarly, disease incidence
of macadamia racemes
was negatively correlated with temperatures above 22′C (Hunter and
Rohrbach, 1969).
OBJECTIVES AND POTENTIAL BENEFITS - Data gathered thus far by the principle
investigator
dearly shows that modification of the microenviromnent can reduce incidence
of disease caused by
B. cinerea. Data presented in the background information section of
this proposal show that heated
air forced into a dense plant canopy via perforated PVC pipe placed
within a stock plant geranium
canopy for 6 hours per day reduced stem blight and sporulation of B.
cinerea. Similarly, heated
air forced into a dense plant canopy via a perforated plastic tube
under an open-bottom bench
located within a commercial greenhouse 24 hours per day effectively
reduced stem blight and
sporulation of B. cinerea. However, in order to incorporate this technology
into current
computerized environmental control units and minimize costs, the minimum
level and duration of
temperature and relative humidity necessary to interrupt the disease
cycle of B. cinerea on
senescent leaves and wounded stems must be defined. Therefore, the
following objectives have been
deemed:
1. Verify where known and determine where not known, the level and duration
of
temperature and relative humidity necessary to interrupt the disease
cycle of B. cinerea on (a)
necrotic geranium leaves and (b) wounded stems of geranium stock plants.
(See background
information section for update).
2. Based upon studies conducted under objective 1, construct computerized
software to
regulate the level and duration of temperature and relative humidity
necessary to interrupt the
disease cycle of B. cinerea. (See background information section for
update).
3. Validate the computer software within a research and commercial
greenhouse.
In the 1970’s, energy and labor costs increased dramatically, physical
facilities aged, and
the ability of the industry to absorb an exploding information base
and, hence, to adopt any
increasingly complex technology, declined. This allowed other nations
to gain a competitive edge
and for the first time in our history, imports from other countries
commanded a significant portion
of our market. As we move toward the 21st century, a concerted effort
must be made to regain the
initiative. Many of the issues are related to market access and marketing,
but improving demand
will not meet the challenge if that demand is supplied by lower cost
inputs.
Only through the production of a cost-effective, high quality produce
delivered in the
quantities wanted and at the time they are wanted will the industy
become revitalized. To achieve
this goal, the following two objectives must be met: (1) pathogen-free
planting stock, and (2)
computerized plant growth optimization strategies. This research proposal
pertains to the
achievement of both of these goals.
Increasing the number of stock plants per unit area could increase the
production of
cuttings. If spacing of stock plants could be decreased without an
increase in B. cinerea, cutting
quality and production could increase the competitiveness of U.S. growers.
A stock plant system
is envisioned whereby heated air can be forced into a dense geranium
canopy at critical intervals
for specific durations to interrupt the disease cycle of B. cinerea
on senescent leaves and wounded
stems. The applications of the forced heated air could be accomplished
via perforated plastic tubes
underneath an open-bottom bench or PVC pipes placed on top of the pots
within the plant canopy.
Once the environmental parameters preceding an epidemic are gathered
and formulated as
a predictive model, this information could be utilized in any growing
system. In crops where a
dense canopy is not formed, it is probable that altering the RH and
or temperature would be
adequate for averting an epidemic when environmental conditions would
otherwise be favorable.
MATERIALS AND METHODS
Objective 1. Verify where known and determine where not known the level
and duration of
temperature and relative humidity necessary to interrupt the disease
cycle of B. cinerea on (a)
necrotic geranium leaves and (b) wounded stems of geranium stock plants.
Dry B. cinerea conidia will be used as inoculum. Conidia will be collected
from 10 to 14-day
old sporulating cultures into a pipet under a very low vacuum and tapped
out of the pipet onto
weighing paper. A conidia settling tower will be used to inoculate
the plant material.
a1) Influence of Temperature on Conidia Germination and Infection. Four
plants will be
inoculated and placed in the dew chamber for 24 hours at 15, 20, 25′C.
One leaf per plant will be
chosen on the basis of age (oldest leaf). Four 1-cm2 leaf pieces will
be removed from the leaf
specimen, fixed in formalimacetic add (FAA) stained and examined. Conidia
with swollen germ
tube tips and hyphae within lesions will be counted.
a2) Conidia Germination Rate on Leaf Surfaces. Plants will be inoculated
and placed in the dew
chamber at 15, 20, and 25′C. After 1, 2, 4, 6, 8, 10, 12, and 24 hours,
4 1-cm2 leaf pieces from one
previously selected leaf of each of 4 plants will be removed, fixed
in FAA, stained, and germinated
conidia counted.
a3) Longevity of Conidia on Leaves. Plants will be inoculated and placed
in a growth chamber at
15, 20, and 25′C with 60 + 10% RH and a 16 hour photoperiod. After
0, 1, 2, 4, or 8 days, 6 plants
will be removed from the growth chamber and incubated for 36 hours
in a dew chamber at 15, 20,
25′C with a 12 hour photoperiod. The number of lesions per plant will
be counted and percent leaf
area infected will be determined with a leaf area meter 24 hours after
removal from the dew
chamber.
a4) Influence of Dew Period on Hyphal Development. Inoculated plants
will be placed in the dew
chamber for 2, 4, and 6 days of continuous dew at 15, 20, 25′C with
a 12 hour photoperiod.
Randomly identified leaf sections containing lesions will be removed
from the plants, fixed in FAA,
cleared in 70% ethanol and stained in 1% aqueous trypan blue. Lengths
of hyphae will be measured
with an ocular micrometer.
a5) Influence of Dew Period and Temperature on Lesion Production. A
group of 24 plants will be
inoculated and placed in a dew chamber at temperatures of 15, 20, and
25′C. Six randomly
identified plants will be removed after exposure to 5, 10, 20, and
40 hours of continuous dew and
moved to a growth chamber set at the same temperature as the dew chamber
treatment with 60 +
10% RH and 16 hour photoperiod. Lesions will be counted on each plant
after variable times in
the dew chamber and growth chamber total 72 hours. Percent leaf area
infected will be determined
with a leaf area meter.
a6) Influence of Timing of Dew Period Interruption on Lesion Production.
Plants will be
inoculated and incubated in a dew chamber at 15, 20, or 25′C for 2,
4, 8, 16, and 24 hours.
Incubation periods are to be followed by 2 hours without dew in a 15,
20, or 25′C growth chamber
at 50 + 10% RH and continuous light. Following the interruption period,
plants will be moved back
to the dew chamber for the remainder of the 24 hour incubation period.
Inoculated and
noninoculated controls will remain in the dew chamber for 24 hours.
The number of lesions will
be counted after an additional 24 hours in the growth chamber. During
the 24 hours in the growth
chamber, a 16 hour photoperiod will be implemented. Percent leaf area
infected will be determined
with a leaf area meter.
a7) Influence of Interrupted Dew Periods on Lesion Production
Inoculated plants will be incubated without light in a dew chamber
for 6 hours and then transferred
to a growth chamber at 15, 20, or 25′C, RH of 65 + 10% and continuous
light. After 30, 60, 90,
120, and 150 minutes in the growth chamber, 6 replicate plants for
each interruption period will
be returned to the dew chamber for the remainder of the 24 hour incubation
period. Noninoculated
controls will remain in the dew chamber for 24 hours. Lesions will
be counted after an additional
24 hours in the dew chamber. Percent leaf area infected will be determined
with a leaf area meter.
During the 24 hours in the dew chamber, a 12 hour photoperiod will
be implemented.
The experiment will be repeated by interrupting the dew chamber environment
for 4, 8, 12,
and 24 hours after which the plants will be returned to the dew chamber
for an additional 48 hour
incubation period. During the 48 hours in the dew chamber, a 12 hour
photoperiod will be
implemented.
a8) Influence of Humidity During an Interruption. Inoculated plants
will be placed in the dew
chamber for 6 hours. Six replicate plants will be removed and placed
in the growth chamber at 30,
60, and 90% RH and continuous light for 20 minutes and returned to
the dew chamber for the
remainder of the 24 hour period. Control plants will remain in the
dew chamber for the remainder
of the 24 hour period. Control plants will remain in the dew chamber
continuously for 24 hours.
Lesions will be conducted after an additional 24 hours in the growth
chamber. During the 24 hours
in the growth chamber, a 16 hour photoperiod will be implemented. Percent
leaf area infected will
be determined with a leaf area meter.
b1-8) Studies Investigating Infection and Progression of B. cinerea
on Wounded Stems of Stock
Plants. Experiments described above utilizing leaf tissue will also
be conducted with wounded
stems. Disease progress will be monitored by measuring visual darkened
lesions on the stem.
Microscopic observations will be conducted using the scanning electron
microscope. Cuttings will
be excised from stock plants 2 cm above a plant node using flame sterilized
razor blades. Dry B.
cinerea conidia will be used as inoculum. Transverse cuts will be made
at a plane 5 mm from the
inoculated surface with flame-sterilized blade. Samples will be fixed
in 3% glutaraldehyde in 0.15M
sodium cacodylate (pH 7.1) and refrigerated overnight. All samples
will be postrixed in osmium
tetroxide vapors for 1 hr, followed by a graded ethanol dehydration
series and storage in 100%
ethanol at room temperature for 15 hours prior to drying. Stem samples
to be observed along the
longitudinal axis will be cryofractured and subsequently thawed in
100% ethanol. All samples will
be critically point dried using bone dry liquid carbon dioxide. Dried
samples will be mounted onto
13 mm aluminum stubs with adhesive tabs and silver dag, then sputter
coated with 42 mn of gold.
The prepared stubs will be examined with a scanning electron microscope
and representative
photomicrographs taken.
Objectives 2 and 3. To be accomplished during years 2 and 3 of project.
Based upon studies
conducted under objective 1 and data collected during 1984-1987 from
a commercial greenhouse and
information based on growth chamber experiments and research greenhouse
studies, construct
computerized software to regulate the level and duration of temperature
and relative humidity
necessary to interrupt the disease cycle of B. cinerea. Validate the
computer software within a
research and commercial greenhouse.
The interpretation of information gathered in objective 1 and 2 is being
used to develop
algorithims. In addition, environmental parameters and corresponding
atmospheric concentrations
of conidia collected during 1984-1987 is being analyzed. Dr. Mel Lacy
of the department of Botany
and Plant Pathology at Michigan State University has recently formulated
a commercially accepted
program to time fungicide sprays for control of Botrytis squamosa that
causes leaf blight of onion
using a conidial release predictor (Lacy, 1991). Due to the high rate
of success and acceptance of
this program among onion growers, a similar strategy will be employed
for B. cinerea on geraniums
and other ornamental crops. This predictive system is envisioned to
be based on a table with
sporulation index values and will be created from data collected from
1984-1987 and from studies
conducted in years 1 and 2 of this proposal. Average temperature and
average vapor pressure
deficit during the previous 72 hours will be used to establish a threshold
to trigger a spray or
modify the environment. The precision of the algorithims will be evaluated
within a research and
commercial greenhouse. The precision of the algorithims will be evaluated
within a research and
commercial greenhouse.
FACILITIES AND EQUIPMENT AVAILABLE Much of the equipment necessary for
this research
project is located in the investigator’s laboratory or in the Department
of Botany and Plant
Pathology located in the Plant Biology Building. Laboratory equipment
includes laminar flow hoods,
autoclave, distilled water system, clinical centrifuge, pH meter, incubated
orbital shaker, 2
incubators, phase contrast and inverted phase contrast microscopes,
analytical balances and
miscellaneous instruments and supplies. The facilities include a greenhouse
(14,000 sq. ft.)
containing 12 benches and is equipped with supplementary lighting.
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Cline, M.N., and Neely, D. 1983. Wound-healing process in geranium
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Gladioulus in the United States in relation to temperature and humidity.
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BUDGET - The following budget is proposed to fund the conclusion of
the second phase and the
initiation of the third phase of this proposal:
Fungal Culture Media and Petri Plates $ 600
Greenhouse Supplies: Fertilizer, Media, Pots $ 900
Computer Programmer $ 7,020
($9.00/hr x 15 hr/wk)
Graduate Student Stipend/Technical Support $12,500
Scanning Electron Microscopy Usage $ 1,500
($10.00/hr beam time)
Growth and Dew Chamber Usage and Supplies $ 1,800
($50/unit/month x 3 units)
Total $24,320
PROJECT LEADER QUALIFICATIONS- Dr. Mary Hausbeck graduated from The
Pennsylvania
State University (PSU) under the direction of Dr. S.P. Pennypacker,
a noted epidemiologist. She
earned a B.S. in Horticulture and completed a M.S. in Horticulture/Plant
Pathology under the
direction of Drs. R.D. Heins and C.T. Stephens at The Michigan State
University (MSU). Dr.
Hausbeck completed a 6 month post-doctoral project involving the tomato
spotted wilt virus
(TSWV) on ornamentals at PSU prior to her appointment as a Visiting
Assistant Professor at MSU.
Her current responsibilities at MSU include greenhouse crops. She is
the senior author on 5
manuscripts published in refereed journals concerning crown and root
rot of geraniums caused by
pythium ultimum documenting etiology, symptomatology, fungicide efficacy,
and cultivar resistance.
She is also the senior author on 3 published manuscripts and 3 manuscripts
in review, all of which
address various aspects of Botrylis cinerea. A Disease Note and manuscript
concerning TSWV on
greenhouse crops are also published. There are 9 published abstracts
concerning her work on
greenhouse crops.
SUMMARY - Controlling disease caused by B. cinerea through modification
of the greenhouse
environment is an attractive addition to traditional control methods.
Although event-driven,
interactive computers are available with the capacity for predicting
disease epidemics and altering
the greenhouse environment, the data base necessary for the development
of software that will
provide predictions is lacking. Data gathered thus far clearly show
that environmental modification
will not only reduce B. cinerea among stock plants, thereby reducing
stem blight and increasing
cutting production, but that the leaf blight on the cuttings removed
from these stock plants will also
be limited. Heated air can be forced into a dense geranium canopy at
critical intervals for specific
durations to interrupt the disease cycle of B. cinerea on senescent
leaves and wounded stems. The
intervals and duration of the heated air could be regulated by a computerized
environmental
monitoring system. This method of growing stock plants would allow
an increased number of stock
plants per unit area and increase the production and quality of cuttings.
Altering the
microenvironment among closely-spaced stock plants to interrupt the
disease cycle of B. cinerea
could apply not only to geraniums, but to all growing systems utilizing
stock plants for cutting
production. However, in order to incorporate this technology into current
computerized
environmental control units and minimize costs, the minimum level and
duration of temperature
and relative humidity necessary to interrupt the disease cycle of B.
cinerea on senescent leaves and
wounded stems must be defined. Therefore, the following objectives
have been outlined; 1) Verify
the level and duration of temperature and relative humidity necessary
to interrupt the disease cycle
of B. cinerea on geranium stock plants, 2) Construct computerized software
to regulate the level and
duration of temperature and relative humidity necessary to interrupt
the disease cycle of B. cinerea,
and 3) Validate the computer software within a research and commercial
greenhouse. Upon
successful completion of this project a forecasting system will be
developed and will provide growers
with an economical disease management tool that improves plant quality
and decreases costs by
reducing disease and pesticide applications.
