Evaluation of Calcium Chloride for Control of Botrytis Fruit Rot on Strawberry
Principle Investigators:
Michael E. Ellis, Professor, Plant Pathology
Larry V. Madden, Professor, Plant Pathology
Omer Erincik, Graduate Student, Plant Pathology
Abstract:
Botrytis fruit rot (gray mold) is the most economically important disease of strawberry in Ohio and
the world wide. Over 90% of all fungicides used on strawberry are for control of this disease.
Recent studies on other crops have indicated that calcium salts, primarily calcium chloride are
effective for controlling fruit rots and other diseases caused by Botrytis. Of significance to this
proposal is that many strawberry growers across the Midwest are currently using calcium
chloride in bloom and preharvest sprays and claim to be getting substantial disease control. At
present, there is no data to support the use of calcium chloride for Botrytis control on strawberry.
The purpose of this research is to develop scientific data to support or disprove the benefits of
calcium chloride for disease control on strawberry. If calcium chloride is effective, its use could
be considered as a cultural practice (foliar nutrient) and would greatly reduce current fungicide
use resulting in less deposition of fungicide in the environment as well as significant economic
savings to growers. If we can demonstrate positive benefits, the use of calcium chloride for fruit
rot control will be directly incorporated into our current extension recommendations for strawberry
disease control.
Results obtained from field studies conducted in spring of 1996 indicate the foliar applications of
calcium chloride had no effect on control of Botrytis fruit rot or on fruit firmness, color, soluble
solids or titratable acidity. Greenhouse experiments will be conducted in winter of 1997 to study
the effects of calcium chloride on these fruit quality characteristics under more controlled
conditions. Field experiments will be repeated in spring of 1997 so that results can be published
in a referred journal. Although our results indicate that the use of calcium chloride does not
control Botrytis fruit rot, it is important to confirm these results so that growers are aware of the
efficacy of this treatment.
Field studies conducted in spring 1996
Methods:
A field trial was established at Maurer's strawberry farm at Wooster, OH. Plots consisted of 4
rows, 1 meter long. All treatments were replicated 4 times in a completely randomized block
design. Calcium chloride was applied at the rate of 4.5 lb/A starting at early (25%) bloom and
repeated 4 times at 4-day intervals. A higher rate (9 lb/A) was applied at 50% bloom and 10 day
later when green fruit were present. Ronilan (a standard fungicide for Botrytis control) was
applied according to current recommendations for comparison and one treatment was left
untreated to serve as the control. All plots were inoculated with a conidial suspension of Botrytis
cinerea at 50% bloom. Plots were harvested 3 times and the percentage of marketable and
Botrytis infected fruit was recorded. Twenty five fruit per replication for each treatment were
evaluated for post-harvest disease development in the laboratory. Fruit were placed in 5 liter
plastic humidity chambers and observed for 10 days for Botrytis infection. Ten fruit per replication
were evaluated for fruit firmness, color, soluble solids and titratable acidity in Dr. Joe Scheeren's
laboratory using standard techniques.
Results:
Much of the data is currently being analyzed. Field data on efficacy of calcium chloride on control
of Botrytis fruit rot are presented below.
| Treatment |
Yield total |
Total fruit |
% Marketable |
% Gray mold |
|---|
|
weight (kg) |
number |
fruit |
infected fruit |
|---|
| CaC'2 4.5lb/A |
16.2 a |
1475 a |
77.6 b |
17.9 a |
|---|
| CaC'2 9 lb/A |
16.1 a |
1427 a |
72.5 b |
21.6 a |
|---|
| Ronilan 2 lb/A |
16.9 a |
1204 a |
95.9 a |
3.6 b |
|---|
| Untreated Control |
16.7 a |
1383 a |
74.2 b |
19.2 a |
|---|
All data in the above table are based on the combined results from 3 harvests. Numbers within
columns followed by the same number are not significantly different.
The data indicate that calcium chloride did not provide control of Botrytis fruit rot at both rates
tested. Ronilan provided excellent control. Although data is still be analyzed, it appears that
calcium chloride had no effect on post-harvest development of Botrytis, or any other fruit quality,
parameters we measured. Data on post-harvest disease development and effects on fruit quality
characteristics will be sent in a supplement to this report as soon as the data is fully analyzed.
We feel that it is important to verify these results by repeating the field trial in 1997. We will
request one more year of funding in order to complete this study.
For further information contact Michael E. Ellis Professor, Dept. of Plant Pathology, OARDC or the Ohio IPM Office.
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