Mango powdery mildew control with triforine

Material Information

Mango powdery mildew control with triforine
Series Title:
Homestead AREC research report
McMillan, Robert Thomas, 1934-
Agricultural Research and Education Center, Homestead
Place of Publication:
Homestead Fla
University of Florida, Agricultural Research and Education Center
Publication Date:
Physical Description:
3 leaves : ; 28 cm.


Subjects / Keywords:
Mango -- Diseases and pests -- Florida ( lcsh )
Powdery mildew diseases -- Florida ( lcsh )
Fungicides -- Florida ( lcsh )
Mangoes ( jstor )
Powdery mildew ( jstor )
Fungicides ( jstor )
government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )


General Note:
"December 14, 1982."
Statement of Responsibility:
R.T. McMillan.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
72801712 ( OCLC )


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I 0

f hf Homestead AREC Research Report SB82-4

sB. Mango Powdery Mil

R. T.

December 14, 1982

dew Control With Triforine

McMillan, Jr. AG {I(

Plant Pathologist
University of Florida, IFAS
Agricultural Research and Education Center
Homestead, Florida 33031


JAN 1 0 1983

Powdery mildew of mango (Mangifera indica L. ) caused by a species of Oidium occurs
each year in Southern Florida resulting in varying degrees of damage to the trees
and their crop (4). Yields can be significantly reduced when the primary cycle of
the fungus begins during flowering but is no longer a problem after the fruit has
set. Powdery mildew has always been considered a minor disease problem of mango,
however over the decades there have been years like 1954 and 1955 that mango bloom
in orchards from the areas of Stuart, Merritt Island and Miami were severely attacked

Foliar fungicides are potentially valuable for the control of powdery mildew of mango
when serious disease development begins early in the flowering season. No fungidices,
other than sulfur, are currently available in the United States to fill this need
although triforine has been used experimentally outside the U.S. (2). Benomyl, which
was formerly highly effective for the control of powdery mildew on mangos (1) is now
no longer used because the Oidium organism has become resistant to this chemical.

The present investigation was performed to determine the effectiveness of triforine
in controlling Oidium on Mangifera indica.

Materials and Methods

Eight tests using single tree plots replicated
cultivar were carried out. The mango cultivar
was 'Tommy Atkins'. The three fungicides used
lbs a.i./acre and 1.6 Ibs a.i./acre and sulfur
25W at 1.5 lbs a.i./acre. All fungicides were
rate of 400 gal/acre. Spray applications were
December 29, 1982, through April 20, 1982.

three times for each treatment and
used as test host for powdery mildew
were triforine 22L at rates of 0.8
6F at 4.75 lbs a.i./acre and dinocap
applied by an airblast sprayer at the
made every 14 days commencing on

Powdery mildew intensity was rated visually by estimating the percentage of leaf
area and number of panicles with mildew lesions and assigning values between 0 and
100 with 0 = no mildew and 100 = powdery mildew lesions of 90% or more of the leaves
or panicles being rated. Number of fruit were counted from each tree within each
plot. The percent of leaves and panicles was arrived at from the evaluation of 100
leaves and panicles from each treatment and cultivar replicated 3 times. Total
number of fruit were counted from each treatment and cultivars replicated 3 times.
All data were subjected to analysis of variance and the means were compared by
Duncan's multiple range test.

Results and Discussion

Incidence of Oidium sp. in the test plots was considerably higher in the untreated
than in the treatments. Triforine was significantly better than sulfur and dinocap
which were equally effective for disease control on the leaves and were 4 to 6 times
* more effective compared to the control. The 50 to 80% incidence of powdery mildew
on the unsprayed panicles was much higher than the 20 to 30% infested leaves. How-
ever the percent disease control in the panicles followed the same pattern as in the
foliage with significant difference between triforine and sulfur and dinocap and the
control (Table 1 & 2). The fungicidal activity of triforine on Oidium sp. agreed

with the observation of Palti et al (2). Number of fruit from each of the treatments
were always greater than those from the unsprayed plots but the differences were not
statistically significant (Table 3).

There were no toxic effects observed with any of the chemicals tested. However, it
has been noted on occasion in uncontrolled field trials with growers that dinocap was
toxic to the panicles. This could possibly be attributed to too high a concentration.
Sulfur is an effective fungicide for Oidium control but has the disadvantage of
causing skin irritation to people who apply it.

These results indicate that it is possible to protect mango from powdery mildew with
sulfur which is an available, EPA approved chemical, as well as with two additional
chemicals that will require further study and testing.

At the present, triforine and dinocap do not have an ERA or a Food and Drug label for
use on mango. However, the EM Industries, Inc. of New York is seeking an EPA label
through IR-4 a national agricultural program; clearances of pesticides and biologies
for minor or special uses.

Literature Cited

1. McMillan, R. T., Jr. 1973. Control of anthracnose and powdery mildew of mango
with systemic and non-systemic fungicides. Trop. Agr. 50:245-248.

2. Palti, J., Y. Pinkas and Mathilda Chorin. 1974. Powdery mildew of mango.
Plant Dis. Reptr. 58:45-49.

3. Ruehle, G. D. 1956. A note on powdery mildew of mango. Proc. Fla. State.
Hort. Soc. 68:277-278.

4. Ruehle, Geo. D. and R. Bruce Ledin. 1960. Mango growing in Florida. pp. 72-75.
Agric. Ext. Service, Gainesville, Florida, Bul 174.


Table 1. Effect of fungicides on leaf infection of 'Tommy
Atkins' mango by Oidium sp.

Percent infection
Treatment rate of leafx'y
Fungicide (Ibs a.i./acre) 'Tommy Atkins'

Control 0 32.7 a
Sulfur 6F 4.75 5.1 b
dinocap 25WP 1.5 5.6 b
triforine F 0.8 0.3 c
triforine F 1.6 0.2 c

Table 2. Effect of fungicides on panicle infection of
'Tommy Atkins' mango infected by Oidium sp.

Percent infection
Treatment rate of paniclex'y
Fungicide (Ibs a.i./acre) 'Tommy Atkins'

Control 0 87.4 a
Sulfur 6F 4.75 3.0 b
dinocap 25WP 1.5 3.1 b
triforine F 0.8 0.2 c
triforine F 1.6 0.1 c

Table 3. Effect of fungicides on yield of 'Tommy Atkins'
mango infected by Oidium sp.

Mean number
Treatment rate of fruit Y
Fungicide (Ibs a.i./acre) 'Tommy Atkins'

Control 0 160 a
Sulfur 6F 4.75 185 a
dinocap 25WP 1.4 181 a
triforine F 0.8 192 a
triforine F 1.6 195 a

XMean of each treatment and cultivar replicated 3 times.

YMeans in a column followed by the same letter do not differ
significantly at the 0.05 level using Duncan's multiple
range test.