The weather here in Connecticut has been woefully wet and cool this June. Heat loving plants of peppers, basil, tomatoes and cucumbers are at a stand still, not growing much. Vegetables preferring cooler temperatures are providing extended harvests rather than bolting. Lettuce, broccoli and spinach have given me bumper crops. My snap peas are just plumping up. Lawns are lush and green, growing fast. These are positive benefits of a long wet spring. The negative is more plant diseases.

          Fungal disease loves it moist. Red Thread (Laetisaria fuciformis), is appearing on many lawns as the environmental conditions are perfect for its development and growth; 65 to 70°F and lots of moisture. Preferred host grasses are fine leaf fescues and perennial rye with bluegrass a close second. These grasses make up of most of our lawns!

Red Thread, photo from Penn State U.

Red Thread, photo from Penn State U.

          Symptoms begin as water-soaked patches with green blades of grass turning tan as they dry and die. Yellow patches are irregular in shape with size varying. As the disease progresses the fungus produces red mycelium ‘threads’. From a distance the lawn appears to have red patches. This is stage when most folks panic looking for a control measure. A change in weather is the basic answer. Less moisture will stop the progression of the disease. Since we can’t control the weather, there are a few things that can be done to help the lawn.

Red Thread, photo from OSU

Red Thread, photo from OSU

          Don’t touch the grass when it is wet. No mowing, walking, spreading fertilizer or aerating. Mowers, equipment and shoes are the biggest offenders of dispersing the spores of Red Thread. Wait until the lawn is dry to work on it all. Fungicides are not recommended or very effective against this disease.

Prevention and a strong healthy turf growing in a pH of 6.5 to 7 is recommended. Red Thread prefers grass growing in low nitrogen. Have a soil test done (www.soiltest.uconn.edu) to determine pH and nutrient levels of the soil supporting your lawn. Use a balanced fertilizer if needed. When lawn is dry, mow and collect the clippings to bag or compost to reduce spreading the spores. Later in the season, resume mulching mowing, leaving the clippings to return nitrogen to the soil.

          Red thread affects the blades of grass, not the roots. Plants will outgrow the disease when they start to grow faster with warmer weather. Avoid watering late in the day and increase airflow to aid in drying of turf. If over seeding bare spots, use Red Thread resistant varieties of perennial ryegrass (Lowgrow, Lynx, Navajo, Passport, Precision, Rivierra II, Shining Star, Target), fine fescue (Biljart, Bighorn, Reliant, SR 3000, Waldina), and Kentucky bluegrass (Ascot, Classic, Dawn, Eclipse, Princeton, Trenton).

          Powdery Mildew prefers the same cooler wet weather as Red Thread. My garden is showing large patches of the white coating on susceptible phlox, peony and the lilacs. Each species has a different variety of fungus for the different plants, but all the symptoms are the same so we call them all powdery mildew even though, technically, it is a different fungus on phlox than on lilac.

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          The disease starts with white patches on the upper surface of leaves, sometimes spreading to stems and growing tips. Leaves eventually yellow then brown. Powdery mildew doesn’t kill plants, but can severely weaken them and put them into premature dormancy.

          The best defense against powdery mildew is to grow resistant varieties of plants. Phlox ‘David’ is known to rarely, if ever, be affected. Other varieties of phlox are Alpha, Blue Boy, David, Orange Perfection, Prime Minister, Starfire. Resistant lilac varieties are the Himalayan, Meyer, Litleleaf, Korean Early, Persian, Japanese Tree, and Swegiflexa Lilacs. I have not found any named varieties of peonies claiming resistance to powdery mildew.

          Prevention of powdery mildew for all plants begins with proper spacing and good air circulation. Divide and separate overgrown plants. Good sanitation in fall includes cleaning up and removing old foliage that may contain fungal spores. Remove infected leaves during the growing season to reduce inoculums and stop spread of any disease. Fungicide spray labeled for use against powdery mildew may be beneficial on plants that have a history of infection in your garden. A common recipe of one teaspoon baking soda in one quart water with 2 tablespoons of vegetable oil mixed in a spray bottle, then sprayed on plant leaves before spots appear is used as a protective measure. Commercially available fungicides containing the chemical ingredients Captan or copper hydroxide are listed as a control measure. Also listed as an effective fungicide against powdery mildew are Bacillus subtilis, lime-sulfur spray, and neem. This last group is least harmful to the environment but still effective.

 
Powdery mildew on phlox. photo by Carol Quish

Powdery mildew on phlox. photo by Carol Quish

 

powdery mildew on phlox, photo by Carol Quish

powdery mildew on phlox, photo by Carol Quish

 
 
 
 
 
 
 
 
 
 
 
 
 
 
One last item! I have had several calls this week about a strange black and orange insect of varying descriptions. After some probing questions, the insects were identified as the larval stage of lady beetles. These are good guys, beneficial insects that feed on other soft bodied insects like aphids! Take a look at the photo below so you can recognize them and be thankful if they visit your garden instead of trying to kill them!
 
 
                                                                    
Lady Beetle Larvae - Good Guy!
Lady Beetle Larvae – Good Guy!
 
 
 
 

– Carol