Date 8/31/93

Title of Project The Effect of Modifying the Microenvironment Among Geranium Stock Plants

on Botrytis Blight and Sporulation of Botrytis Cinerea

Institution where work is being conducted Michigan State University

Amount of Endowment Grant $17,000
Covering Period 1/1/93 to 12/31/93

Anticipated Date of Project Completion/Final Report 12/31/94

Individual(s) Conducting Project:

(List Project Leader First)

Dr. Mary K. Hausbeck - Title Assistant Professor

Telephone Number (517) 355-4534

The Effect of Modifying the Microenvironment Among Geranium Stock Plants Within a Greenhouse on

Botrytis Blight and Sporulation of Botrytis Cinerea

Mary K. Hausbeck

Michigan State University

Progress Report to the American Floral Endowment, 9/1/93

A. Project Objectives:

The production of a cost-effective, high quality product

delivered in the quantities desired and at the time they are needed will enable

the floriculture industry to 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 pertains to the

achievement of both of these goals.

B. Summary of Work Conducted:

The objective that was targeted in the recent research period

pertains to the first of these objectives by comparing novel fungicides that

could be effectively incorporated into a disease forecasting system with those

commonly used for the control of B. cinerea.

Rooted cuttings were treated with the fungicide Curalan 50DF/8 oz

(vinclozolin) alone or in combination with the surfactant LABS 114/1.0% v/v using

a hand held pump sprayer. Additional treatments included the surf actant LABS 114

alone, and untreated controls. Cuttings were inoculated with a conidial

suspension (1.0 x 10^4) of a B. cinerea isolate within 24 hours of the fungicide

treatment. Following inoculation, cuttings were maintained under high relative

humidity to encourage disease development. Treatments were reapplied 14 days

after the first application. Disease severity was assessed 7, 14, and 21 days

following inoculation by counting the numbers of leaves infected, leaves with

sporulating B. cinerea, and plant death caused by B. cinerea. In a subsequent

experiment, two experimental fungicides from Ciba-Geigy were trialed as described

above.

Over the course of the experiment, disease severity as measured by the

incidence of leaves with sporulating B. cinerea was significantly limited by the

combination treatment of LABS114 + Curalan 50DF in comparison with Curalan 50DF

alone and the untreated inoculated control. Although not statistically

significant, LABS 114 alone or in combination with Curalan 50DF limited plant

death in comparison to Curalan 50DF alone and both untreated controls. The

incidence of geranium leaves blighted was not significantly affected by any of

the treatments. However, given the high incidence of latent infections (>60%)

that developed from infections initiated while in the stock plant greenhouse

(prior to fungicide applications) indicated by the untreated, uninoculated

control, it is not surprising that a fungicide application was unable to reduce

the occurrence of Botrytis blight. More importantly, the inability of the

treatments to effectively limit the occurrence of leaf blight further emphasizes

the importance of effective management strategies including environmental

manipulation and/or fungicide applications to be employed at all stages of crop

production. In additional testing, the two experimental fungicides from Ciba-Geigy,

were equally effective as the standard fungicide Chipco 26019 WDG and

should offer new, effective choices for fungicidal control in the future.

C. Future Plans Covered by the Endowment Grant:

Plans are underway

to test a Botrytis sporulating

index in a commercial greenhouse among geraniums. This system would identify

those environmental conditions favorable for the sporulation of Botrytis, thereby

triggering the application of fungicides and/or the alteration of the environment

to avert the epidemic. By applying fungicides when most needed, plant quality

will be insured, costs will be reduced, and the threat of fungicide resistance

will be minimized. Efforts will be continued to investigate novel and developing

fungicides for the control of Botrytis.

D. Anticipated Benefits for Floral Industry:

Controlling disease caused by B.

cinerea through modification of the greenhouse environment is an attractive

addition to traditional control methods. Although event-drive, 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. The environmental

parameters necessary to deter Botrytis blight will be formulated into forecasting

system to provide growers with an economical disease management tool that

improves plant quality by reducing disease and pesticide applications and cost.

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