Entomosporium Leaf Spot: The Fungus Among Us

As winter transitions into spring here in California, the temperatures rise, but the rains remain. You may be gardening in a short sleeved shirt, but your boots are still caked with mud.

Another unpleasant consequence of this combination of wet and warm: a leaf spot disease on many evergreen and deciduous plants, entomosporium.

If there is spotting on the leaves, and the leaves are falling, it could be entomosporium, a fungus that pops up during warm, wet, late winter-early spring weather. 

Entomosporium on Photinia x fraseri

Entomosporium is a fungal disease that spots the leaves of plants in the Pomoideae group of the rose family, including apple, flowering crab apple, evergreen pear, hawthorn, pear, photinia (especially photinia!), pyracantha, quince, Rhaphiolepis (Indian hawthorn, among others), and toyon. 

Indian Hawthorn with Entomosporium

According to the UC Davis Integrated Pest Management website, entomosporium appears as tiny reddish spots, sometimes surrounded by a yellow halo, appear on the leaves of infected plants, usually on older growth. These spots darken and enlarge as the leaves mature. Spore-forming bodies eventually appear in the center of the spots; these dark fruiting bodies may appear to be covered with a glossy membrane, beneath which white masses of spores may be visible. Infected plants may prematurely drop many leaves.

If that is the case, remove infected leaves from the ground and the shrub. Also, avoid overhead watering. Making sure there is room between the plants for good air circulation can help. If that is impractical, try removing some of the lower branches.

Toyon with entomosporium

Toyon / entomosporium

 

In overwhelming situations, the experts at UC say to remove any ground covers beneath the plant, which may harbor the fungus. It might not be a bad idea to replace any mulch that is there, as well.

 The folks at the Plant Pathology Department at North Carolina State University offers these common sense tips:

• Purchase plants showing no leaf spot symptoms. 

• Isolated healthy plants or hedges can often remain healthy as the spores are only splashed over short distances. Space plants to improve the air movement around the plants and promote rapid drying of leaf surfaces.

• Do not water or fertilize plants any more than necessary to avoid promoting excess new growth. 

• Reduce pruning during the summer which promotes continual new growth. 

• It may be necessary to remove severely diseased plants and replace them with another plant species that is not susceptible to leaf spot. (Life is too short to put up with a problematic plant)

Alabama Cooperative Extension reports that in recent
trials in Alabama, the Indian hawthorn cultivars, ‘Dwarf Yedda’, ‘Olivia’, ‘Indian Princess’, ‘Snow White’, and Raphiolepis. x delacourii, have shown excellent resistance to this disease.

The good news: as drier weather takes hold here (and you avoid overhead watering), the entomosporium may go into hiding...until next year. Entomosporium fungi that infect deciduous plants overwinter mainly as spores on fallen leaves or as mycelia within tissue. On evergreen hosts, the fungi may remain on leaves year-round. Fungi are spread from infected tissue or contaminated leaf litter to healthy leaves by splashing raindrops or overhead irrigation. The pathogens are most severe during wet weather, especially when it coincides with new plant growth, according to UC.

In other words, the plant can tolerate it in most situations, if you help it along by a thorough cleanup of infected leaves and careful watering. The question is: can YOU tolerate it? In the larger scheme of all things horticultural, you have bigger bugs to battle.