|
| Quince rust on mayhaw fruit |
Quince rust is caused by the fungus Gymnosporangium clavipes. Fruits in the pome fruit group (apples, quince, pear and mayhaws) 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 and junipers and part on the mayhaw.
In mayhaws 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.
Management of quince rust would start with planting a selection of mayhaws that have resistance to the disease. If you already planted a susceptible selection, then the elimination of cedar and junipers close to the mayhaws would reduce the amount of fungal spores that could cause an infection. This may not be very practical. A fungicide application from the time the flower buds begin showing color through bloom would help manage the disease. Fungicides available are sulfur or myclobutanil. Copper fungicides may be used but not during bloom. For more information on control with fungicides,call our office at 318-435-7551 or refer to the Louisiana Plant Disease Management Guide located on the LSU AgCenter Web site.