Managing Diseases of Ornamentals with Bicarbonates and Determining their Mode of Action Progress Report — March 1993
Date March 1, 1993
Title of Project Managing Fungal Diseases of Ornamentals and Determining Their Mode of Action
Institution where work is being conducted Cornell University
Amount of Endowment Grant $ 20,000
Covering Period 1/09/92 to 28/02/93
Anticipated Date of Project Completion/Final Report 31 December 1994
Individual(s) Conducting Project:
(List Project Leader First)
R. K. Horst - Title Professor
Telephone Number 607/255-7894
H. W. Israel - Title Senior Research Associate
Managing Fungal Diseases of Ornamentals and Determining Their Mode of Action
R. K. Horst and H. W. Israel
Cornell University
- A. Project Objectives:
- 1. Which consequential diseases of ornamentals can be managed with bicarbonates?
- 2. What is the minimal effective bicarbonate treatment necessary for management ofrose powdery mildew?
- 3. What is the mechanism(s) by which bicarbonate antagonizes Sphaerotheca pannosavar. rosae?
- B. Summary of Work Since Project’s Inception (1 January 1992):
- Efficacy Studies: Our research has shown that bicarbonate solutions and horticultural oils, both”natural” substances with antifungal properties, are excellent candidates for
biocompatible treatment of diseased plants. Moreover, we now have a liquid
formulation which contains bicarbonates as active ingredients along with non-petroleum
oil spreader-sticker supplements which is more efficacious and less
phytotoxic.
- Mechanism Studies: We continue to use the experimental methods previously described and havedetermined bicarbonates to be both preventive and eradicative in their activity.
- C. Results to Date:
- Efficacy Studies: A liquid formulation containing both sodium and potassium bicarbonate as activeingredients and inactive ingredients consisting of fatty acids which contain spreader-sticker
characteristics for spreading the spray on leaf surfaces has shown even better
efficacious control of powdery mildew than bicarbonates and oil. Moreover, the
formulation is less phytotoxic than the bicarbonate/oil combination. The active
ingredients in the formulation are applied by weekly sprays of 0.5% concentration
of bicarbonates. Tbis formulation will be registered with EPA for commercial use.
- Mechanism Studies: To discover whether bicarbonates can prevent primary infections of rose by thepowdery mildew, we compared germination percentages of <24 h-old conidia
incubated in near-saturated atmospheres on agar/collodion coated glass microscope
slides that received one preinoculation runoff spray of 0.08 M KHCO3 (0.5%
concentration) versus water. We also microscopically evaluated structural integrity,
indicative of viability, of conidia 1 h following submersion in KHCO3 Solutions Of
0.00 up to 0.64 M. Sprays reduced germination by 22%, and higher percentages of
conidia exhibited injury with increasing molarity of the KHCO3 Solutions. We infer
that sprays applied at very low concentrations become virtually 100% efficacious at
the very high concentrations that result from cyclic dehydration/rehydration of their
residues during changing atmospheric water vapor pressures.
- D. Future Plans Covered by the Endowment Grant:
- 1. In vitro tests in our laboratory show bicarbonates to be effective against species ofFusarium Colletotrichum, and Alternaria. We also now can add Botrytis to this list.
Our search will continue.
- 2. We are continuing our thorough investiations on the mechanism of activity.
- E. Anticipated Benefits for Floral Industry:
- The bicarbonates which we term biocompatible chemicals will have an excitingimpact on disease control. An application will be made to EPA to register a
formulation we now have.
