Carol Pinnell-Alison | 5/8/2009 8:21:57 PM
Quince rust is caused by the fungus Gymnosporangium clavipes. Fruits in the pome fruit group (apple, quince, pear and mayhaw) are susceptible. A unique aspect of this disease is that the eastern red cedar and some junipers are essential for the continuation of the disease from year to year. The fungus completes part of its life cycle on the cedar or junipers and part on the mayhaw.
In mayhaw, the fruit is affected, and on cedar trees, cankers are formed on the twigs, limbs or trunk. The mayhaw fruit infected with the fungus will look spiny with a coating of orange powdery fungal spores. The mayhaw fruit is susceptible to infection by the fungus as the blossoms open and until shortly after petal-fall. The correct temperature and moisture for the fungal spores to germinate and infect the blossoms must occur for there to be an infection.
Unfortunately there are no mayhaw varieties that have resistance to quince rust. The elimination of cedars and junipers close to the mayhaws would reduce the amount of fungal spores that could cause an infection. This may not be very practical, however. A fungicide application from the time the flower buds begin showing color through bloom would help manage the disease. The only fungicide active ingredient available over the counter to homeowners is myclobutanil. Read the product label to make sure the product is labeled for quince rust and mayhaw. Follow the mixing instructions and pre-harvest interval.
For more information call our office at 318-435-7551 or click here for the Commercial Mayhaw Disease Control Guide.
The LSU AgCenter and the LSU College of Agriculture