Question: Why are some of my mango flowers turning dark?
Answer: This is a common question this time of year. According to University of Hawaii at Manoa plant pathologist specialist Scot Nelson, the symptoms you see are caused by a fungus that first appears as a white powder on the flowers and eventually turns infected flowers brown and dry enough to crumble in your hand.
Sanitation practices and early treatment are recommended for home gardeners to control mango powdery mildew, which is more common in lower-rainfall areas. If you see this fungus on your mango flowers, it will most likely recur every year thereafter.
Practicing sanitation now will suppress the fungus and decrease infection on a yearly basis. Remove severely infected flower panicles (flower branches) and consistently pick up fallen leaves and dispose of them in a rubbish can.
Some home gardeners maintain compost piles. However, because most home garden compost piles do not reach temperatures high enough to kill fungal pathogens (135 to 150 degrees Fahrenheit), branches and leaves should be put in a green-waste bin or rubbish can.
Nelson provides more information in his report "Mango Powdery Mildew," at www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-46.pdf. Call the UH Master Gardener help line at 453-6055 if you want the report mailed to you.
Backyard sanitation practices can be used to suppress many fungal, bacterial and viral diseases that flourish in the year-round warmth of the tropics. Regularly applying these practices will help to control these diseases, preventing the loss of produce and requiring fewer chemical treatments. Remove dead or diseased plants, dispose of fallen leaves and rotten fruit, maintain a consistent watering routine and choose appropriate plants for your elevation and humidity and precipitation rates.
Learn more by attending the College of Tropical Agriculture and Human Resource’s annual plant sale from 9 a.m. to 12 p.m. Feb. 14 at the Urban Garden Center, 955 Kamehameha Highway. The plant sale will include hand-picked potted roses by the Honolulu Rose Society. For information on the sale, visit www.ctahr.hawaii.edu/ougc or call 453-6050.
Jayme Grzebik is an urban horticulturist with the University of Hawaii College of Tropical Agriculture and Human Resources’ Cooperative Extension Service and statewide coordinator for the UH Master Gardener Program. She can be reached at grzebik@hawaii.edu.
