Damage to large, vigorously growing trees is often aesthetic. Carbaryl, cyfluthrin, imidacloprid and malathion are insecticdes labeled for control of this pest. Quince fruit affected by quince rust. Rusts have been very serious on hawthorn trees in Missouri in recent years. Cedar apple and hawthorn rusts cause bright- yellow spots on the foliage.
Quince rust is more damaging.
It affects fruit, twigs and petioles, causing galls of twigs and pet ioles. The undersides of the yellow leaf spots, fruits and galls bristle with aecia when the rusts are producing spores. Aecial cups of quince rust on quince. Although they can be controlled with fungicides, in the long term, it may be necessary to replace hawthorns with other flowering and fruited trees, such as disease-resistant crabapples. University Outreach and Extension does not endorse commercial products.