Plant Disease
Aug. 2008
PD-46
Mango Powdery Mildew
Scot C. Nelson
Department of Plant and Environmental Protection Sciences
named mango cultivars worldwide there is considerable
T wo fungal diseases of mango (Mangifera indica L.)
flowers and young fruits, mango powdery mildew
and mango anthracnose, are the primary causes of the
variation in fruit size, color, shape, flavor, texture, and
taste. Often called “the king of fruits,” mango grows
widespread problem of poor mango fruit set and yield throughout the tropics and subtropics and is one of the
in Hawai‘i. world’s most important fruit crops.
Worldwide, mango powdery mildew is a sporadic
but very severe disease of mango leaves, panicles, and Pathogen
young fruits; up to 90 percent crop loss can occur due to Oidium mangiferae Berthet (a fungus), causing powdery
its effect on fruit set and development. Mango powdery mildew of mango, is widely distributed throughout the Pa-
mildew was present in India before 1874; it was first cific region. It infects panicles, fruits, and leaves. Mango is
reported in Hawai‘i in 1983. the only known host of the mango powdery mildew patho-
Mango powdery mildew is an easily recognizable gen (i.e., only mango can be infected by the fungus).
problem; the symptoms are very apparent and are diag-
nostic. However, it is not easily controlled with cultural Symptoms on panicles
practices alone. If susceptible mango cultivars are grown Infected panicles (flowers, flower stalks, and young fruits)
in mildew-prone areas, growers should expect the disease become coated with the whitish powdery growth of the
to recur yearly or seasonally. To achieve good yields, such pathogen (photo, below). Infected flowers and fruits even-
growers must act with control measures during flower- tually turn brown and dry. The dead flowers can easily
ing, before it is too late to prevent the loss of the current crumble in one’s hand. Infection often causes flowers
season’s crop.
In Hawai‘i, powdery mildew tends to occur yearly
in areas where this disease predominates and must be
controlled in order to obtain acceptable fruit yields.
Powdery mildew is more common in lower-rainfall ar-
eas than in higher-rainfall areas. For example, it is the
predominant disease of mango in lower-rainfall West
Hawai‘i (South and North Kona), whereas anthracnose is
the predominant fruit disease of mango in higher-rainfall
East Hawai‘i (Hilo area, Puna district).
Host
Mango (family Anacardiaceae) is a perennial, branching,
evergreen tree approximately 30–40 feet tall at maturity.
The mango fruit is a large, fleshy drupe that contains a
laterally compressed stone. Among the several hundred Mango panicles with powdery mildew
All photos by S. Nelson
Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in coopera-
tion with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mänoa, Honolulu, Hawai‘i 96822.
An equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, age, religion, color, national origin, ancestry, dis-
ability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. CTAHR publications can be found on the Web site <http://www.ctahr.hawaii.edu/freepubs>.
UH–CTAHR Mango Powdery Mildew PD-46— Aug. 2008
A whitish-gray haze covers a normally reddish mango panicle. This haze is the diagnostic symptom of mango powdery
mildew, caused by Oidium mangiferae. This fungus can infect and colonize all parts of the panicle, including flowers and
young fruits. Infected young fruits may have a purplish haze. Here, the disease is so advanced that it may be too late for any
control measures to have an effect upon poor fruit set and yield. All photos by S. Nelson
Symptoms of mango powdery mildew and mango anthracnose compared. Left, powdery mildew caused by Oidium
mangiferae: panicles have a whitish-gray haze; killed flowers turn brown and gray. Right, anthracnose caused by Colletotrichum
gloeosporiodes: black, pin-prick spots on flowers and panicles; killed flowers turn inky black.
UH–CTAHR Mango Powdery Mildew PD-46— Aug. 2008
Table 1. Mango flowering stages and their susceptibility to infection by powdery mildew (Oidium mangiferae)*
Flowering stage Description of stage Susceptibility
Bud swell to bud break Initial stage No
Mouse-ear Elongation of basal bracts and emergence of inflorescence No
Protected Elongation of inflorescence still protected by bracts Yes
Green-colored Further elongation of inflorescence and opening of secondary rachi,
flowers still in bud stage Yes
Red-colored Final elongation of inflorescence and reddening of rachi Yes
Red-open Individual flowers start opening from base Yes
Full-bloom All individual flowers and inflorescence open Yes (most susceptible)
Fruit-set First visible fruits Yes
Pea-sized fruit Fruits approx. 8 mm diameter Yes
*After: Schoeman, M.H., and B.Q. Manicom. 1995. Epidemiology of powdery mildew on mango blossoms. Plant Disease 79:524–529.
and small fruits to abort and fall off. Fruits that become spots may form on leaves (photo below, center). On very
infected after they have set have purple-brown blotchy susceptible cultivars, the youngest leaves may become
lesions that crack and form corky tissue as the fruitlet completely covered with fungal spores and mycelium, and
enlarges. The full-bloom stage is the most susceptible to eventually die (photo below, left). On some cultivars, the
infection (Table 1). whitish residue of the fungus tends to appear on the lower
leaf surface, along the leaf midrib (photo below, right).
Symptoms on leaves
On some cultivars, new flushes of growth and younger Pathogen dissemination
leaves are highly susceptible and may curl up and become Conidia of O. mangiferae are wind-disseminated from
distorted. Older leaves are more resistant to infection. other mango trees or from within an infected tree’s
Grayish, necrotic lesions or large, irregularly shaped canopy.
Characteristic symptoms of mango powdery mildew on mango leaves
UH–CTAHR Mango Powdery Mildew PD-46— Aug. 2008
Table 2. Some fungicides registered in Hawaii for controlling powdery mildew of mango (source: Hawaii Pesticide
Information Retrieval System)
Example of product name* Active ingredient(s) Formulation
70% Neem Oil (other products Clarified hydrophobic neem oil (70%) Soluble concentrate
contain this ingredient)
Bi Carb Old Fashioned Fungicide Carbonic acid, monopotassium salt (82%) Soluble concentrate/solid
Biocover MLT Kerosene (petroleum) hydrodesulfurized (98%) Oils, no added pesticide
Biocover UL Aliphatic petroleum solvent (98%) Oils, no added pesticide
Drexel Sulfur 90W Sulfur (90%) Wettable powder/dust
Kaligreen Carbonic acid, monopotassium salt (82%) Soluble concentrate
Rally 40 WSP Myclobutanil (40%) Water-soluble pouch
*Other products with the same or similar active ingredient may be available, these are only examples.
Source: Hawaii Pesticide Information Retrieval System.
The environmental conditions for spread of powdery Integrated disease management practices
mildew occur across a broad daily range of temperature Integrated management of mango powdery mildew in
(50–88°F, 10–31°C) and relative humidity (60–90%). Hawai‘i consists of four general approaches:
These conditions commonly coincide with mango flower- • choice of mango cultivars
ing in Hawai‘i, which explains why powdery mildew is • cultural practices
such a widespread and entrenched problem in the state. • plant nutrition
For infection (the penetration of host tissues by germ • fungicide sprays.
tubes of the pathogen) the optimum condition is ap-
proximately 73.4°F (23°C) plus high relative humidity Cultivar selection
followed by an abrupt reduction of relative humidity. This Mango cultivars vary in susceptibility to powdery mildew
can occur in Hawai‘i where cool nights are followed by (Table 2). The use of less susceptible cultivars is the best
warm days. control measure for this disease. For the very susceptible
Airborne conidia of O. mangiferae land upon suscep- cultivars, most of the flowers, very young fruits, and
tible host organs, the spores produce germ tubes, and the young leaves can become severely diseased. Check with
germ tubes infect the tissues. The fungal mycelium of the your neighbors to learn which cultivars perform well in
pathogen ramifies within and upon host tissues, eventu- your area.
ally killing host cells and absorbing their contents. The
fungus produces spores abundantly all over the surface of Cultural disease management practices
affected tissues (it is the abundant fungal mycelia and the Choose hot, dry areas for mango cultivation; if possible,
conidia and condiophores on the surface of host tissues avoid areas that consistently have rain during the flow-
that creates the typical “powdery mildew” appearance ering season. Prune plants to keep flowers within the
of mildewed plants). range of spray equipment and to improve air circulation
O. mangiferae survives on infected plants and for a in the canopy. Pick up fallen mango foliage and destroy
period of time as conidia on fallen mango plant debris. it, remove severely infected panicles. Intercrop mango
Populations of O. mangiferae can build up rapidly during with other fruit trees or forestry species. Keep tall weeds
seasonal flushes of new mango leaves and flowers. The away from mango trees. Cut back or prune unwanted or
conidia can be transported long distances by winds. competing adjacent tree species, allowing more sunlight
UH–CTAHR Mango Powdery Mildew PD-46— Aug. 2008
Table 2. Susceptibility of some mango cultivars to mango Mango cultivars that have been recommended by
powdery mildew UH-CTAHR for Hawai‘i based on their horticultural
properties
Slightly
Carrie Gondo Ah Ping
Sensation Banana Fairchild
Tommy Atkins Gouveia
Harders
Keitt (MS)
Moderately
Momi K
Haden Rosa
Pope
Mabroka Graham
Rapoza
Lippens Divine
Smith Peter All of these cultivars are productive and have superior quality fruit.
Keitt Hilacha Flowering occurs from December to April in Hawai‘i, but off-season
Glenn Bocado flowering is common. Growers may have to use fungicide sprays to
Pico deLoro Edward control powdery mildew on these varieties in some locations.
Martinique Mango criolla
Springfels Fresca
Very
Zill Alphonso every 7–14 days thereafter until fruit set.
Kent Amini The fungicides registered for control of mango pow-
Bullock’s Heart Labich
dery mildew in Hawai‘i fall into several groups based
Mistakawi Apple
Pairee Blackman upon their active ingredients: clarified hydrophobic neem
Faizanson oil; mono- and dipotassium salts of phosphorous acid;
carbonic acid, monopotassium salt; kerosene (petroleum)
Adapted from Nishijima, W. 1994. Mango diseases and their control. hydrodesulfurized; aliphatic petroleum solvent; sulfur;
p. 20–24 in: Proceedings: Conference on Mango in Hawaii. March 9– mancozeb; and myclobutanil.
Sprays of wettable sulfur or sulfur dusts provide
11, 1993, College of Tropical Agriculture and Human Resources.
reasonable control of powdery mildew, but may cause
phytotoxicity (“burn”) to flowers and young fruit where
sprays are applied during sunny, warm conditions.
and air circulation. Fertilize the tree as required to pro- A systemic fungicide, Rally 40 WSP (myclobutanil),
mote vigorous growth. was labeled for use in Hawai‘i in 2008 for mango pow-
dery mildew. This is a supplemental label, which growers
Plant nutrition practices and applicators must obtain from the pesticide distributor
Foliar applications of phosphate fertilizer solutions (i.e., and have in their possession when applying the product.
monopotassium phosphate, 0.5% KH2PO4), alone or in It is very important to follow label instructions and to
combination with conventional powdery mildew fungi- practice fungicide resistance management practices.
cides, is reported to provide economical and effective Where a grower is spraying to control mango anthrac-
results in Israel and South Africa. nose caused by C. gloeosporiodes, the products used for
that may provide some incidental control of powdery
Fungicides mildew, while not being labeled for that use.
The most effective way to control mango powdery mil- Baking soda (sodium bicarbonate) mixed with water is
dew on very susceptible cultivars is to apply well timed an old home-remedy spray for powdery mildew. However,
fungicide sprays. Most of the fungicides registered for because baking soda is not labeled as a fungicide, it may
powdery mildew control on mango in Hawai‘i can be not legally be used for disease control, according to Hawai‘i
effective. Department of Agriculture regulations. Some growers
The first spray application should occur no later than report that foliar sprays of milk can be effective against
at 50% of full flowering, and spraying should continue powdery mildew, but the same use restriction may apply.
UH–CTAHR Mango Powdery Mildew PD-46— Aug. 2008
Managing large trees Nofal, M.A., and W.A. Hagga. 2006. Integrated manage-
A reasonable goal is to protect the panicles within har- ment of powdery mildew of mango in Egypt. Crop
vesting reach from mildew. A problem faced by many Protection 25: 480–486.
backyard growers is how to deliver a fungicide spray Oosthuyse, S.A. 2000. Cost reduction of powdery mildew
to flowers that are high on the tree. They may lack the control in mango with mono potassium phosphate. p.
high-pressure equipment and training needed to deliver 719–723 in: Proc. Sixth International Mango Sympo-
the spray past a certain height. One should always be sium, Acta Horticultura.
careful when applying pesticides, and also should seek Pernezney, K., and R. Ploetz. 2000. Some common
professional assistance if there is any question about diseases of mango in Florida. Plant Pathology Fact
doing the spraying work or renting equipment related to Sheet PP-23, Florida Cooperative Extension Service,
pesticide applications. Institute of Food and Agricultural Sciences, University
of Florida. http://plantpath.ifas.ufl.edu/takextpub/Fact-
References Sheets/pp0023.pdf.
American Phytopathological Society, list of mango Ploetz, R.C., G.A. Zentmeyer, W.T. Nishijima, K.G.
diseases and pathogens. www.apsnet.org/online/com- Rohrbach, and, H.D. Ohr (eds). 1994. Compendium
mon/names/mango.asp. of tropical fruit diseases. APS Press, The American
Burnett, H.C. 1975. Powdery mildew of mango. Plant Phytopathological Society, St. Paul, Minnesota.
Pathology Circular 156, Florida Dept. of Agriculture Reuveni, M. 2000. Efficacy of trifloxystrobin (Flint),
and Consumer Services, Division of Plant Industry. a new stroliburin fungicide, in controlling powdery
www.doacs.state.fl.us/pi/enpp/pathology/pathcirc/ mildews on apple, mango and nectarine, and rust on
pp156.pdf. prune trees. Crop Protection 19: 335–341.
Chia, C.L., R.A. Hamilton and D.O. Evans. 1997. Mango. Reuveni, M., and R. Reuveni. 1995. Efficacy of foliar
UH-CTAHR. 2 p. www.ctahr.hawaii.edu/oc/freepubs/ sprays of phosphates in controlling powdery mildews
pdf/HC-2.pdf. in field-grown nectarine, mango trees and grapevines.
Morton, J. 1987. Mango. p. 221–239 in: Fruits of warm Crop Protection 14: 311–314.
climates. Julia F. Morton, Miami, Florida. Schoeman, M.H. and B.Q. Manicom. 1995. Epidemiol-
Nelson, S.C. 2008. Mango pest and disease image gallery. ogy of powdery mildew on mango blossoms. Plant
www.ctahr.hawaii.edu/nelsons/mango. Disease 79:524–529.
Nishijima, W. 1994. Mango diseases and their control. UH-CTAHR Crop Knowledge Master (Mango). www.
p. 20–24 in: Proceedings: Conference on Mango in extento.hawaii.edu/kbase/crop/crops/i_mango.htm.
Hawaii. March 9–11, 1993, University of Hawai‘i at UH-CTAHR list of mango pests. www.extento.hawaii.
Mānoa, College of Tropical Agriculture and Human edu/Kbase/crop/crops/mango.htm
Resources.
Acknowledgments
Fred Brooks, UH-CTAHR, and Brian Bushe, UH-
CTAHR, for reviews of this manuscript.
