Hawthorne

Lace bug feeding Leaves become mottled yellow-green. Leaves have black spots of insect excrement, especially on lower surface. Insecticides are warranted if the tree is small or under stress. Damage to large, vigorously growing trees is often aesthetic. Carbaryl, cyfluthrin, imidacloprid and malathion are insecticdes labeled for control of this pest.
Cedar apple rust
Hawthorn rust
Quince rust (the Gymnosporangium rusts fungi)
Photo of tree containing gymnosporangium rusts fungi.

Photo of quince fruit affected by quince rust.
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.
Photo of aecial cups of quince rust on quince.
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. Fungicides labeled for these rusts are chlorothalonil, chlorothalonil plus fenarimol, mancozeb, myclobutanil, propiconazole, thiophanate-methyl, thiophanate-methyl plus mancozeb and triadimefon.
University Outreach and Extension does not endorse commercial products. Follow the label on all pesticides.

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University Outreach and Extension Email: plantclinic@missouri.edu