Symptoms of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Even during global pandemics, it’s a joy to be outside during the great north Florida spring we’ve been experiencing lately. As cold fronts come through with their rain bands, some packing a punch, they leave behind the most pleasant mornings, clear blue daytime skies, and crisp evenings. Unfortunately, we’re not the only organism that also enjoys those cool days. Many species of fungi are quite active this type of year as the rains, followed by warmer, yet not too hot temperatures, create the perfect conditions for fungal growth. Some of these fungi grow right on or in the plants we’d like to be enjoying for ourselves, stealing nutrients and causing plant decline or merely causing aesthetic damage. As this is an active time for certain species of fungi, local extension offices are getting more calls and questions regarding lawn and landscape damage due to fungal pathogens. A recent call was a new one for me and an example of a native fungi-plant interaction that looks bad but requires no intervention from us. It also highlights how correctly identifying a disease leads to the best action and can often save time and money and prevent unnecessary pesticides (in this case a fungicide) from entering the environment.
Close up of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
The fungi and plant involved here was the oak leaf blister (Taphrina caerulescens) on a swamp chestnut oak (Quercus michauxii). It forms, you guessed it, blisters on the leaves of any of the oaks, though live oak (Quercus virginiana), laurel oak (Quercus laurifolia), and water oak (Quercus nigra) seem to be preferred hosts. The spores of the fungi, dormant since the previous summer/fall and which happen to get lodged in bud scales through wind and rain, germinate in cool, wet weather. The fungus then infects young leaves as they flush and its growth causes a disruption in the leaves’ development. This leads to the blistered look of the leaf tissue and, during extended periods of cool, wet weather, the entire leaf sort of shrivels, browns, and eventually falls off. Spores are eventually released from the fallen leaves to start the process over the next spring.
Severe oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Though the leaves look pretty terrible, this fungal disease rarely causes plant health issues and the tree recovers just fine. Specimen trees that experience it year to year may be treated with a fungicide, but most homeowners can just let it go. Raking up and disposing of the leaves may help prevent further infections by reducing the number of spores released in the area.
As you enjoy another cool morning after an evening rainstorm, remember that the fungi all around you are also having a great day. You may want to look at your landscape plants and see if there’s anything abnormal going on. If so, take a photo and send it to your local extension office for help with identification and best methods of control, or, like in this case, just leaving it alone.
p.s. As I said this was a new one for me and I want to thank Stan Rosenthal, Extension Agent emeritus, for assisting with identification.
In times like these, it seems that our own perceived “problems” pale in comparison to the “big picture.” In my day-to-day work, I have the opportunity to help people solve problems with their landscapes, lawns and gardens. I enjoy the problem solving part of my job as an extension agent.
Winter annual weeds in lawn in early spring. Photo credit: Larry Williams
You’d be surprised how upset some people can be about a few weeds, a dying petunia or a tomato with a crack in it. They’ll let small things like this upset their entire world. It’s as if they think we live in a perfect world when it comes to expectations for the plants in their own landscape.
It has become apparent to me that too many people spend too much time letting too many small things bother them too much.
When my twin sister, Linda, and I were growing up in a small town in middle Georgia, an elderly couple (Mr. and Mrs. Hunt) would crack pecans and give the shelled halves to us to eat. They’d hand the shelled pecans to us over the fence that separated our yards. At five or six years old this was a treat for my sister and me.
I remember their landscape. I remember Mrs. Hunt sweeping their dirt driveway lined with coconut sized rocks. She used handmade brooms. I remember their pink flowering dogwoods in spring. I remember their old-fashioned yellow and orange daylilies during summer. I remember the fascination of seeing red spider lilies seemingly come from nowhere in the fall underneath deciduous trees as they displayed their autumn colors. I remember Mrs. Hunt letting me smell a flower from a sweetshrub plant, which reminded me of sweet apples. The deep red blooms and dark green leaves of this shrub complemented the white wooden wall on the east side of their home.
Mulberry tree with fruit. Photo credit: Larry Williams
I remember climbing a large mulberry tree in their backyard and picking and eating the berries. I remember watching Mr. Hunt prune grapevines growing on an overhead trellis. I remember learning about the history of a ginkgo tree planted just outside a chicken pin in their side yard. I remember watching hummingbirds flying in and out of the reddish orange funnel-shaped blooms of a large trumpet vine growing on an old metal frame of a water tank.
I don’t remember the weeds, even though I know there must have been weeds in the Hunt’s landscape. I know there was the occasional pecan that didn’t fill out or that was worm infested. And I’m sure an occasional plant had to be replaced. But these are not the things that made lasting impressions for me.
The big picture is not the weeds, the dying petunia plant or the pecan with a worm in it. Sure you will have weeds in your yard and certain plants that don’t survive. Just don’t let these things become the source of worry. In my opinion, a landscape should be a source of pleasure, a place to learn and a place to pass along lasting memories. Besides, with all the things there are to worry about in this world (as recent days have revealed), why let your own backyard be one of them?
One of the things to do while stuck at home due to COVID-19 restrictions, is to look for caterpillars and butterflies in your landscape. I’ve noticed giant swallowtail butterflies (Papilio cresphontes) a little early this year. The giant swallowtail is one of the largest and most beautiful butterflies in our area. Its larval stage is known as the orangedog caterpillar. This unusual name comes from the fact that it feeds on young foliage of citrus trees.
Orangedog caterpillar. Photo credit: Donald Hall, University of Florida
The orangedog caterpillar is mostly brown with some white blotches, resembling bird droppings more than a caterpillar. When disturbed, it may try to scare you off by extruding two orange horns that produce a pungent odor hard to wash off.
I’ve had some minor feeding on citrus trees in my landscape from orangedog caterpillars. But I tolerate them. I’m not growing the citrus to sell. Sure the caterpillars eat a few leaves but my citrus trees have thousands of leaves. New leaves eventually replace the eaten ones. I leave the caterpillars alone. They eat a few leaves, develop into chrysalises and then emerge as beautiful giant swallowtail butterflies. The whole experience is a great life lesson for my two teenagers. And, we get to enjoy beautiful giant swallowtail butterflies flying around in our landscape and still get plenty of fruit from the citrus trees. It is a win, win, win.
In some cases, the caterpillars can cause widespread defoliation of citrus. A few orangedog caterpillars can defoliate small, potted citrus trees. Where you cannot tolerate their feeding habits, remove them from the plant. But consider relocating the caterpillars to another area. In addition to citrus, the orangedog caterpillars will use the herb fennel (Foeniculum vulgare) and rue (Ruta graveolens) as a food source. Some butterfly gardens plant citrus trees to provide food for orangedog caterpillars so that they will have giant swallowtail butterflies. So you could plan ahead and grow some fennel, rue or find a butterfly garden in your area for the purpose of relocating the larvae.
Yellow giant swallowtail butterfly on pink garden phlox flowers. Photo credit: Larry Williams
The adult butterflies feed on nectar from many flowers, including azalea, bougainvillea, Japanese honeysuckle, goldenrod, dame’s rocket, bouncing Bet and swamp milkweed. Some plants in this list might be invasive.
Keep in mind that mature citrus trees can easily withstand the loss of a few leaves. If you find and allow a few orangedog caterpillars to feed on a few leaves of a mature citrus tree in your landscape, you and your neighbors might get to enjoy the spectacular giant swallowtail butterfly.
Success in the garden can occur with proper watering. Learn several ways to water to your vegetables In the Home Garden with UF IFAS Extension Escambia County.
With our warm weather, many homeowners are looking to create a beautiful lawn for the year. There are so many products in the home improvement stores and nurseries that promise to make your lawn into a green paradise. What to choose?
Photo UF/IFAS Extension. Spring is a good time to check the water flow and direction of a pop-up irrigation system and make adjustments as necessary.
UF/IFAS Extension provides advice based on scientific research. This is what the science says:
Wait to apply lawn fertilizer in north Florida until mid-April. Lawn grasses don’t have sufficient root growth and capabilities to use the fertilizer until then. Applying fertilizer earlier in February and March feeds the winter weeds or is lost to leaching down into the soil below the grass roots. Here’s more detail on fertilizing your lawn.
Weed and feed products are not recommended. Instead, spot treat weeds when they are small before they mature and set seed. Consult our Weed Management Guide.
Preemergence herbicide, if applied correctly, can cut down on the weeds. Apply in late February or first of March for summer weeds and October 1 for winter weeds. Now in late March – Early April is still a good time to use a preemergence herbicide for those weeds that have not yet sprouted. It is crucial to apply the product correctly, following all label directions. Measure your lawn and make sure the right amount of product is applied. This is a convenient way to measure your lawn from your armchair.
Sharpen your mower blades! A clean cut on the grass blade cuts down on lawn stress and diseases setting in.
Water efficiently. We see more damage to lawns from overwatering than underwatering. Overwatering leads to increased weeds, disease, insect pests and weakens grass roots. Lawns need ½” to ¾“ of water and this will tell you how to determine when to water. The root system is healthier and stronger when watered deeply only when it needs it. Learn how long it takes your sprinkler system to deliver that amount.
The University of Florida provides more advice and information at:
