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Copyright 2005, Board of Trustees, University
of Florida

Homestead AREC Research Report SB79-1 February 14, 1979

00 Fungicides for Disease Control on Mangos in Florida

R. T. McMillan, Jr.
( {B Associate Plant Pathologist
University of Florida, IFAS .
Agricultural Pesearch and Education Center
/ Homestead, Florida

The major mango (Mangifera indica L.) diseases cause considerable annual losses,

to Florida growers. With the strict gradd standards in effect control of diseases

causing fruit blemishes and decay has become very important. Most mango diseases

are adequately controlled by various forms of fungicides. Unfortunately disease

control is never flawless because complete coverage is a practical impossibility and

because the rapid growth rate of leaves and fruit exposes unsprayed tissue to in-

fection.

For most of the commercial mango cultivars, anthracnose, caused by Colletotri-

chum gloeosporioides Penz., is probably the most difficult production problem facing

the Florida mango grower.

SMlango anthracnose causes blossom blight, leaf spot, fruit russeting or tear

staining, and fruit rot. Disease damage is closely dependent upon humidity. The

spring rains and/or heavy dews during the critical period for infection greatly in-

creases the disease.

Anthracnose infection in bearing trees takes place from the beginning of the

blossoming period in gradually decreasing severity until the fruit is approximately

half grown. Host of the mature fruit decay has its beginning as latent infections

occurring when the fruits are small. As the fruit matures and ripens, the spots

develop rapidly and cause considerable loss in transit or storage.

Anthracnose on the flower panicle appears at first as small brown or black

spots which gradually enlarge and often coalesce to cause the death of flowers

either directly or indirectly by invasion of the flower stalks.

Infections on young leaves are first noted as small, dark, angular to irregular

* pots which often coalesce to form large necrotic areas which may crack and fall

out. Infections on older leaves usually remain subcircular to angular and less

-2-

than inch in diameter, with fruiting bodies appearing as brown to black dots on

either surface.

The very young fruit are readily infected. Spots on the young fruit may re-

main as pinpoint latent infections but in wet weather may enlarge and sporulation

may occur.

Infections on the green mature to ripe fruits appears as black spots of varied

form, which may be slightly sunken and show surface cracks, and spots may coalesce

to cover large areas.

Latent infections usually penetrate the flesh deeply and cause rotting of the

fruit either preharvest or postharvest. Russeting or tear staining may result from

spores being washed down upon the fruit from an infected twig or flower stalk.

The widespread occurrence of the causal fungus on living as well as dead tis-

sues on mangos makes it impractical in commercial groves to attempt control through

any other means than fungicide sprays. Copper fungicides are of limited value for

anthracnose control. Ruehle and Ledin (6) found that weekly applications of zineb,

maneb, or captain during bloom followed by monthly applications of copper after fruit

set provided anthracnose control. Maneb alternated with zineb and Dithane M45 fol-

lowed with tribasic copper or Dithane M45 used in bloom as well as post bloom pro-

vided good control of anthracnose. However, fruit decay after harvest indicated

that Ditbane M45 was not as effective as copper in controlling latent anthracnose.

In a later experiment Conover (1) found that Daconil and Fermate alone were equal

to maneb alternated with zineb as bloom sprays followed by copper in post bloom.

Fermate and copper were equally effective in post bloom but Daconil was less effec-

tive McMillan (3) found that benomyl at 8 ozs per 100 gallons was superior to 1.5

pounds of maneb per 100 gallons in bloom followed by 3.0 pounds of copper per 100

gallon in post bloom.

In addition to the reduction in fruit infection, yields for benomyl-sprayed

trees were increased indicating significant disease control in the flowers.

-3-
Recent anthracnose control studies (4) found that Benomyl alternated with

maneb plus Triton B-1956 or Nu-Film 17 and benomyl plus Nu-Film 17 were signifi-

cantly better than benomyl alone or benomyl combined with Triton B-1956.

A spreader-sticker added to the sprays aids in obtaining good coverage.

The following spray schedule is recommended for the present:

General Spray Schedule for Control of Anthracnose

Time of Application Fungicide

1. As first panicles are approximately Benomyl 1 to 2 lbs per acre
2 inches.

2. One week after No. 1. "

3. One week after No. 2 and repeat at "
7-day intervals as long as there is
open bloom.

4. At fruit set and not longer than 7 Benomyl 1 to 2 lbs per acre or
days after the last benomyl appli- Hicronized copper 2 to 4 lbs
cation, per 100 gallons of water.

5. Three to four weeks after No. 4 Benomyl 1 to 2 lbs per acre or
until 14 days of harvest with Micronized copper 2 to 4 lbs
benomyl and up til harvest with per 100 gallons of water.
copper.

Powdery mildew caused by a species of Oidium is considered to be a minor

disease on mango in Florida. However, when optimum conditions for this pathogen

prevail during flowering, yield reduction can be serious in commercial groves. In

severe attacks flowers, flower stalks and young fruit are coated with the whitish

powdery growth of the pathogen and the flowers and young fruit turn brown and fall.

The underside of infected leaves and the skin of infected large fruit are

coated with the white growth of the fungus. In some cases leaves may be distorted.

The underside of older infected leaves and the infected skin of mature green fruit

has a purplish brown cast after the white growth wears off.

Powdery mildew has been reported to be controlled by copper fungicides or by

sulfur sprays or dusts (2). For several years benomyl provided outstanding control

-4-
however the fungus now is resistant to the fungicide. Growers have used Karathane

at pound per 100 gallons and reported good control. However, no.tolerance for

SKarathane has ever been established on mango.

The only fungicide now recommended for control of Powdery mildew is 4.75 Ibs

actual sulfur per 100 gallons of water. The first application should be made post

bloom repeated in bloom, at fruit set and 3 weeks after fruit set (5).

Literature Cited

1. Conover, Robert A. 1965. Results of recent experiments on control of mango

anthracnose. Fla. State Hort. Soc. 78:364-369.

2. Lynch, John S. and Margaret J. Mustard. 1956. Mangos in Florida. Department

of Agriculture, Tallahassee, Florida, Bul. 20.

3. McMillan, R. T., Jr. 1973. Control of anthracnose and powdery mildew of mango

with systemic and nonsystemic fungicides. Tropical Agriculture 50(3):245-248.

S4. McMillan, R. T., Jr. 1974. Enhancement of anthracnose control by combining

benomyl with Nu-Film 17. ASHS, Tropical Region 18:135-139.

5. Plant Disease Control Guide. 1971. IFAS, Fla. Coop. Ext. Serv., Univ. of Fla.

6. Ruehle, G. D. and R. B. Ledin. 1960 Mango growing in Florida. Fla. Agr. Exp.

Sta. Bul. 174.

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"This public document was prepared and printed at a cost of
.0040 cents per copy to inform mango growers, agricultural
suppliers and the public of disease prevention and control
:programs for mangos."