Algal leaf spot, also known as green scurf, is commonly found on thick-leaved, evergreen trees and shrubs such as magnolias and camellias. It is in the genus Cephaleuros and happens to be one of the only plant parasitic algae found in the United States. Although commonly found on magnolias and camellias, algal leaf spot has a host range of more than 200 species including Indian hawthorn, holly, and even guava in tropical climates. Algal leaf spot thrives in hot and humid conditions, so it can be found in the Florida Panhandle nearly year round and will be very prevalent after all the rain we’ve had lately.
Algal leaf spot is usually found on plant leaves, but it can also affect stems, branches, and fruit. The leaf spots are generally circular in shape with wavy or feathered edges and are raised from the leaf surface. The color of the spots ranges from light green to gray to brown. In the summer, the spots will become more pronounced and reddish, spore-producing structures will develop. In severe cases, leaves will yellow and drop from the plant.
Algal leaf spot on a camellia leaf. Photo Credit: University of Florida/IFAS Extension
The algae can move to the stems and branches in more extreme cases. The algae can infect the stems and branches by entering through a small crack or crevice in the bark. The bark in that area cracks as a canker forms that eventually can girdle the branch, killing it.
Algal leaf spot on a sycamore branch. (Platanus occidentalis). Photo Credit: Florida Division of Plant Industry Archive, Bugwood.org.
In most cases, algal leaf spot is only an aesthetic issue. If only a few leaves are affected, then they can just be removed by hand. \It is important that symptomatic leaves are discarded or composted offsite instead of being left in the mulched area around the trees or shrubs. If symptomatic leaves are left in the same general area then irrigation or rain water can splash the algal spores on healthy leaves and branches. Infected branches can also be removed and pruned.
Preventative measures are recommended for long-term management of algal leaf spot. Growing conditions can be improved by making sure that plants receive the recommended amount of sunlight, water, and fertilizer. Additionally, air circulation around affected plants can be increased by selectively pruning some branches and removing or thinning out nearby shrubs and trees. It is also important to avoid overhead irrigation whenever possible.
Fungicide application may be necessary in severe cases. Copper fungicides such as Southern Ag Liquid Copper Fungicide, Monterey Liqui-Cop Fungicide Concentrate, and Bonide Liquid Copper Fungicide are recommended. Copper may need to be sprayed every 2 weeks if wet conditions persist.
Algal leaf spot isn’t a major pathogen of shrubs and trees, but it can cause significant damage if left untreated. The first step to management is accurate identification of the problem. If you have any uncertainty, feel free to contact your local Extension Office and ask for the Master Gardener Help Desk or your County Horticulture Agent.
IPM for Shrubs in Southeastern US Nursery Production Volume II is the third book released by the Southern Nursery Integrated Pest Management Working Group (SNIPM) and includes chapters on hydrangea, loropetalum, holly, rhododendron (including azalea), Indian hawthorn, and weed management. Each chapter covers history, culture and management of the major species and cultivars in production, as well as arthropod pest management and disease management. Within the discussion of these topics, each chapter includes strategies for developing effective IPM programs for key pests and plant pathogens, including tables of fungicides and insecticides for use with these key organisms. While developed for nursery producers, this information also may be useful to landscapers, students, arborists and others.
This free book is downloadable as pdf chapters at
The first book, IPM of Select Deciduous Trees in Southeastern U.S. Nursery Production, was released in May 2012 and is available for free download as chapter .pdf files at http://wiki.bugwood.org/SNIPM and as an eBook from the iTunes Bookstore https://itunes.apple.com/us/book/ipm-for-select-deciduous-trees/id541182125?mt=11.
The second book, IPM for Shrubs in Southeastern US Nursery Production Volume I, was released in June 2014 and can also be downloaded as chapter .pdf files at http://wiki.bugwood.org/SNIPM or from the iTunes Bookstore at https://itunes.apple.com/us/book/ipm-for-shrubs-in-southeastern/id903114207?mt=11.
The SNIPM Working Group is a multi-disciplinary group of Extension professionals formed to more efficiently and effectively develop and deliver educational programming to the southern U.S. nursery and landscape industry.
Although we’ve received much-needed rainfall of late, it’s still a struggle to manage moisture levels in our Panhandle landscapes this summer. During wet summer seasons, one recurring issue is that watering plants too much can have as much of an ill effect as not watering enough.
Shallow rooted plants, as well as newly set plants can easily become water stressed. Some people lightly water their plants each day. With this practice, one is only watering an inch or less of the topsoil. Most roots are deeper than this. Instead of a light watering every day, soaking the plant a few times a week works better. A soil that has been soaked will retain moisture for several days. This is a very good practice for young plants. In contrast, some people soak their plants to often. This essential drowns the roots by eliminating vital oxygen in the root zone. This can also cause root rot. Leaves that turn brown at the tips or edges, as well as leaf drop, are displaying signs of overwatering.
The following are tips from the UF/IFAS Florida-Friendly Landscape Program. These tips will help conserve water by providing best management practices for your landscape:
- Choose the right plant for the right place: Be sure to place plants in your landscape that match existing environmental conditions.
- Water Thoughtfully: Water early in the morning and water when plants and turfgrass start to wilt. Refrain from watering in the late afternoon or evening. This is when insects and diseases are most active.
- Perform regular irrigation maintenance: Remember, an irrigation system is only effective if it is maintained regularly. Check for and repair leaks. If using a pop-up heads for turfgrass, point heads away from driveways and sidewalks.
- Calibrate turfgrass irrigation system: Ideal amount of water to apply to turfgrass is ½”- ¾”. A simple test can be done to calibrate. Place a coffee or tuna cans throughout the landscape. Run the irrigation system for 30 minutes. Average the depth of the water containers. Adjust running time to apply the ½”- ¾” rate.
- Use micro-irrigation in gardens and individual plants: Drip, or microspray irrigation systems apply water directly to the root system with limited surface evaporation.
- Make a rain barrel: Rain barrels are an inexpensive way to capture rainwater from your roof. This can translate into a big impact on your water bill as well.
- Mulch plants: Mulch helps keep moisture in the root zone. Two to three inches in-depth, for a few feet in diameter will work well for trees, shrubs, flowers and vegetables.
- Mow correctly: Mowing your grass at the highest recommended length is key. Be sure to cut no more than 1/3 of the leaf blade each time you mow. Keep mowing blades sharp as dull cuts often cause grass to be prone to disease.
- Be a weather watcher: Wait at least 24 hours after a rainfall event to water. If rain is in the forecast, wait 48 hours until irrigating. Use a rain gauge or install a rain shut-off device to monitor irrigation scheduling.
For more information on water conservation principles contact your local county extension office.
Supporting information can be found at the UF/IFAS Center for Landscape Conservation & Ecology’s Drought Toolkit: http://clce.ifas.ufl.edu/drought_toolkit/
Come to this free workshop to learn about the latest results of University of Florida and national research on roses. Receive hands-on training on symptoms and management of rose rosette disease, rose mosaic disease, crown gall, and rose pests.
FL Pesticide CEUs, FNGLA CEUs and GA Pesticide CEUs have been applied for!
This program is geared for nursery and greenhouse growers, landscapers, municipal maintenance personnel, Extension personnel, Rosarians, rose enthusiasts and science teachers. Sponsored by Farm Credit of Northwest Florida and Harrell’s.
To register for this FREE event, please go to: https://rose-diseases-pests.eventbrite.com
Wildflowers near Live Oak, Florida. Image Credit, UF / IFAS
Unfortunately, reports from the National Research Council say that the long-term population trends for some North American pollinators are “demonstrably downward”.
Ten years ago the U.S. Senate unanimously approved and designated “National Pollinator Week” to help raise awareness. National Pollinator Week (June 19-25, 2017) is a time to celebrate pollinators and spread the word about what you can do to protect them. Habitat loss for pollinators due to human activity poses an immediate and frequently irreversible threat. Other factors responsible for population decreases include: invasive plant species, broad-spectrum pesticide use, disease, and weather.
So what can you do?
- Install “houses” for birds, bats, and bees.
- Avoid toxic, synthetic pesticides and only apply bio-rational products when pollinators aren’t active.
- Provide and maintain small shallow containers of water for wildlife.
- Create a pollinator-friendly garden.
- Plant native plants that provide nectar for pollinating insects.
There’s a new app for the last two.
The Bee Smart® Pollinator Gardener is your comprehensive guide to selecting plants for pollinators based on the geographical and ecological attributes of your location (your eco-region) just by entering your zip code. Filter your plants by what pollinators you want to attract, light and soil requirements, bloom color, and plant type. This is an excellent plant reference to attract bees, butterflies, hummingbirds, beetles, bats, and other pollinators to the garden, farm, school and every landscape.
The University of Florida also provides a low-cost app for Florida-Friendly Plant Selection at: https://fyn.ifas.ufl.edu/plants or go on-line to create a list of these same plants at: http://www.floridayards.org/
Not only can you find out which plants attract pollinators, you will be given the correct growing conditions so you can choose ‘the right plant for the right place’.
Remember, one out of every three mouthfuls of food we eat is made possible by pollinators.