Can an overabundance of water on a landscape be a bad thing? It’s the middle of August and many of us who last week were quite happy with the very green turf that more frequent than normal rainfall has given us are now seeing brown spots in the yard and failing bedding plants. Don’t try to fix those problems with more irrigation! That may be the worst thing you can do.
When soil is saturated with water the pore spaces in the soil, which normally hold air, are filled with water. Because plant roots get the oxygen they need from the air in those spaces, the roots can literally drown in a soil that stays waterlogged over an extended period. Plants in such situations become stressed and susceptible to disease. Most of the diseases that attack turfgrass are caused by fungi. The fungi are always in the soil, but they lay dormant until over-saturated soils and wet leaves create the perfect environment for their attack. Unfortunately, unlike insect or weed problems, we don’t get a heads up that a problem may be beginning. Fungi-relate disease symptoms will appear in two common patterns on the lawn, either in a circular patch of browning turf or as spots on the grass blades. Remember, though, that many lawn problems have similar symptoms, so a positive identification of the problem is needed in order to achieve a successful control. So what can you do to help alleviate the situation?
- Turn off your automatic timer if the weather is wet and turn the system back on only when drier conditions occur.
- Install a rain sensor to stop your automatic irrigation system from providing more water when the soil doesn’t need it.
- Mow with a sharp blade to avoid causing tearing wounds on the blade that the grass has to expend energy to heal while it is trying to fight off other disease.
- Don’t over-fertilize. Excess amounts of nitrogen can create less tolerance to environmental stresses and diseases.
- Spot treat the affected area if a fungicide is needed. Fungicides will slow down the fungus growth but will not eliminate or kill it. The fungus will go dormant until the right environment comes along again. Only use fungicides when absolutely necessary.
- Practice the first four cultural steps again to help prevent the fungus from attacking again.
Constant rainy weather can affect bedding plants as well. They may get attacked by above-ground creatures, lose vigor, look wilted, turn yellow and often die. Ways you can help:
- Control pests such as snails and slugs that thrive and reproduce rapidly during rainy weather and chew holes in plant leaves and flowers. Toads should be left alone because they feed on slugs. There also are numerous baits on the market that will help control snails and slugs. You can even place a bowl in the ground up to its rim and fill it half full of beer to attract and drown many snails and slugs.
- Temporarily pull mulch away from around plants to allow the soil to dry faster.
- Use a garden fork to aerate the soil. Push the tines straight down into the soil around the plant and pull it straight out again.
- Improve air circulation by thinning and pruning. This is especially important in shade gardens.
If you are unsure of what is causing your lawn problem, contact the Hernando County Extension office for proper identification before applying any pesticides. For more information on lawn diseases or for plant questions in general, call the Hernando County Master Gardeners at (352) 754-4433 Monday thru Friday from 9 a.m. to 5 p.m.
About the Author: Sylvia Durell is the Hernando County Florida-Friendly Landscaping™ (FFL) Program Coordinator. Her position is funded by the Hernando County Utilities Department and the Southwest Florida Water Management District. She is a Certified Horticulture Professional through the Florida Nursery, Growers and Landscape Association. Ms. Durell is available for presentations to clubs and for “brown bag” lunch programs for employees of Hernando County companies. Call (352) 540-6230 for a list of topics.