For this month’s horticulture article I’d like to share information regarding timely issues in home landscapes as evidenced by the calls and emails I’m currently getting from gardeners. In the Fall of the year — especially if we have a lot of rain — we get numerous calls regarding brown patch disease in lawns. Even though brown patch disease can be problematic in other warm season turf grasses such as centipede and Bermuda, the majority of calls are regarding issues with St Augustine grass. Brown Patch is a fungus disease caused by a pathogen called Rhizoctonia solani. It has been referred to as a spring-and-fall disease since it has a tendency to be more active when we have moderate temperatures (60 – 75 degrees) especially and high moisture. At 80 degrees and above, and under dry conditions, the activity of the fungus decreases significantly. Once temperatures begin to moderate in the fall the first indication of an infection in the lawn is a small-to-moderate irregular brown/tan circle which increases in diameter as temperatures moderate and rainfall increases. Within the circle there are green blades of grass among the tan straw colored grass.
Additionally the grass within the irregular brown circle can be pulled easily because it is rotted at the base. Once a lawn has a history of brown patch disease it is more likely to show up anytime temperatures moderates and there is high moisture. In St. Augustine the grass takes on a yellowish, yellow–orange color, in centipede it will lean more toward a purplish color. Once daytime temperatures reach 80 degrees F or above, even in the summer months there may be areas that get brown patch disease usually in shady areas under or next to trees or in enclosed back yards where there is little air movement. Issues that increase the incidence of brown patch are watering late in the afternoons which allows leaf blade to remain wet overnight. Applying fertilizer past the end of August or fertilizing before the first or second week in April can increase brown patch disease, and thus heavy thatch problems. When brown patch occurs, treat promptly with a fungicide containing one of the following active ingredients. The following fungicides are labeled to control brown patch diseases in lawn grasses, Myclobutanil (Ferti – lome F Stop, Green Light Fung Away, Spectracide Immunox), Thiophanate – Methyl (Ferti – lome Halt, Scott’s Lawn Fungus Control, Southern Ag Systemic Fungicide), Triadimefon (formerly Bayleton, Bayer
Advanced Fungus Control, High Yield Lawn Fungicide). Two applications 10 – 14 days apart provide the best control. On a personal note, let me emphasize that increased rainfall not only interferes with effectiveness of fungicides but it also increases fungus activity. Always follow label instructions in terms of safety, recommended rates and application.
The surge in popularity of citrus in home gardens is at an all-time high due to it being several years since we’ve experienced freeze intense enough to kill mature citrus trees. Satsuma is very popular due to the high quality that can be produced by homeowners and the ease at which they can be peeled because of their loose skin compared to sweet oranges. Keep in mind also that when the decision to plant citrus is made, cold hardiness must be a priority. Kumquats and Satsuma are the most cold hardy with Lemons and Lime being the least cold hardy. Sweet Oranges, Navel Oranges and Grapefruit fall somewhere in between Kumquats and Limes in terms of cold hardiness. One of the most common complaints that I get from homeowners is a condition referred to as puffy fruit in Satsumas. Puffy fruit are mostly a problem on young, vigorous growing Satsuma trees. These fruit are unusually large, have thick rinds and relatively dry flesh. As the tree becomes older, the occurrence of puffy fruit decreases. There is some thought that trees go through a juvenile stage and once passed this stage, fewer puffy fruit are produced. On older mature trees, even though it occurs a lot less, puffiness can occur, but these fruit are thought to be due to late blooms that set fruit during periods of warm weather. Although little can be done to prevent puffy fruit, good growing conditions, proper fertility, pest control, and time will help to reduce this condition. Two of the more popular types of Satsuma are Brown’s Select, which begins ripening in mid–October, and Owari, which produces excellent quality fruit and begins ripening from early to mid–November. The fruit of Satsuma keeps well on the tree and can be picked and eaten over a three-to-four-week period and still maintain quality. However this year, I’m getting a lot of calls from homeowners saying the squirrels are damaging Satsuma on the tree.
A gardener had a question regarding sooty mold on gardenias. The question: “Since sooty mold is the result of sucking insects — in this case white flies producing honeydew that falls on the leaves giving rise to sooty mold growth—what is an effective material to control the whiteflies without harming butterflies, hummingbirds or lizards?”
Sooty mold grows on a variety of ornamental plants in home landscapes; it is non-parasitic and does not penetrate the plant tissue. Sooty mold does, however, prevent sunlight from reaching the leaves thus interfering with photosynthesis. It is a result of sucking insects, such as aphids, mealy bugs, scale and whiteflies, secreting honeydew. Horticultural oils are effective and non–toxic. These kill insects by coating and suffocating them. In this process, it is important to coat the surface and undersides of the leaves. Make three applications, carefully following rates and intervals on the label. It is generally recommended that treating every 10 – 14 days is effective. Also, horticultural oils do not leave behind any toxic residues that would negatively impact butterflies, hummingbirds or lizards.
Happy Gardening!!
Gerald P. Roberts
Additionally the grass within the irregular brown circle can be pulled easily because it is rotted at the base. Once a lawn has a history of brown patch disease it is more likely to show up anytime temperatures moderates and there is high moisture. In St. Augustine the grass takes on a yellowish, yellow–orange color, in centipede it will lean more toward a purplish color. Once daytime temperatures reach 80 degrees F or above, even in the summer months there may be areas that get brown patch disease usually in shady areas under or next to trees or in enclosed back yards where there is little air movement. Issues that increase the incidence of brown patch are watering late in the afternoons which allows leaf blade to remain wet overnight. Applying fertilizer past the end of August or fertilizing before the first or second week in April can increase brown patch disease, and thus heavy thatch problems. When brown patch occurs, treat promptly with a fungicide containing one of the following active ingredients. The following fungicides are labeled to control brown patch diseases in lawn grasses, Myclobutanil (Ferti – lome F Stop, Green Light Fung Away, Spectracide Immunox), Thiophanate – Methyl (Ferti – lome Halt, Scott’s Lawn Fungus Control, Southern Ag Systemic Fungicide), Triadimefon (formerly Bayleton, Bayer
Advanced Fungus Control, High Yield Lawn Fungicide). Two applications 10 – 14 days apart provide the best control. On a personal note, let me emphasize that increased rainfall not only interferes with effectiveness of fungicides but it also increases fungus activity. Always follow label instructions in terms of safety, recommended rates and application.
The surge in popularity of citrus in home gardens is at an all-time high due to it being several years since we’ve experienced freeze intense enough to kill mature citrus trees. Satsuma is very popular due to the high quality that can be produced by homeowners and the ease at which they can be peeled because of their loose skin compared to sweet oranges. Keep in mind also that when the decision to plant citrus is made, cold hardiness must be a priority. Kumquats and Satsuma are the most cold hardy with Lemons and Lime being the least cold hardy. Sweet Oranges, Navel Oranges and Grapefruit fall somewhere in between Kumquats and Limes in terms of cold hardiness. One of the most common complaints that I get from homeowners is a condition referred to as puffy fruit in Satsumas. Puffy fruit are mostly a problem on young, vigorous growing Satsuma trees. These fruit are unusually large, have thick rinds and relatively dry flesh. As the tree becomes older, the occurrence of puffy fruit decreases. There is some thought that trees go through a juvenile stage and once passed this stage, fewer puffy fruit are produced. On older mature trees, even though it occurs a lot less, puffiness can occur, but these fruit are thought to be due to late blooms that set fruit during periods of warm weather. Although little can be done to prevent puffy fruit, good growing conditions, proper fertility, pest control, and time will help to reduce this condition. Two of the more popular types of Satsuma are Brown’s Select, which begins ripening in mid–October, and Owari, which produces excellent quality fruit and begins ripening from early to mid–November. The fruit of Satsuma keeps well on the tree and can be picked and eaten over a three-to-four-week period and still maintain quality. However this year, I’m getting a lot of calls from homeowners saying the squirrels are damaging Satsuma on the tree.
A gardener had a question regarding sooty mold on gardenias. The question: “Since sooty mold is the result of sucking insects — in this case white flies producing honeydew that falls on the leaves giving rise to sooty mold growth—what is an effective material to control the whiteflies without harming butterflies, hummingbirds or lizards?”
Sooty mold grows on a variety of ornamental plants in home landscapes; it is non-parasitic and does not penetrate the plant tissue. Sooty mold does, however, prevent sunlight from reaching the leaves thus interfering with photosynthesis. It is a result of sucking insects, such as aphids, mealy bugs, scale and whiteflies, secreting honeydew. Horticultural oils are effective and non–toxic. These kill insects by coating and suffocating them. In this process, it is important to coat the surface and undersides of the leaves. Make three applications, carefully following rates and intervals on the label. It is generally recommended that treating every 10 – 14 days is effective. Also, horticultural oils do not leave behind any toxic residues that would negatively impact butterflies, hummingbirds or lizards.
Happy Gardening!!
Gerald P. Roberts
Gerald Roberts
Gerald Roberts is a Horticulturist and Master Gardener Program Coordinator for the LSU AgCenter
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