Month: July 2018

Brown Patch and Pythium Blight

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Brown patch (caused by Rhizoctonia solani) and Pythium blight (caused by Pythium spp).

These diseases are often the most severe diseases for cool-season grasses, especially on tall fescue and ryegrass.

Pythium blight has the potential to cause significant damage to turfgrass quickly. The disease starts as small spots, which initially appear dark and water-soaked. Affected turfgrass dies rapidly, collapses, and seems oily and matted. White, cottony mycelia may be evident early in the morning.  The disease is driven by hot-wet weather, which correlates with increased stress on the turf. Similar environmental and cultural factors that encourage brown patch also promote Pythium. Therefore, cultural practices for control of brown patch will also help to minimize Pythium blight development. A correct diagnosis is essential because Pythium control requires specific fungicides.

Several fungicides are available for each of the diseases described above. Consult the Georgia Pest Management Handbook or the Turfgrass Pest Control Recommendations for Professionals (www.georgiaturf.com) for proper fungicide selection and usage. Read the label and follow proper guidelines.


Pythium blight on tall fescue (Photo Lee Burpee)

Brown patch can cause a foliar blight, which results in necrotic leaves and circular brown patches up to 4-5 ft in diameter. High soil and leaf canopy humidity, and high temperatures increase disease severity. Higher than recommended rates of nitrogen in the spring promotes disease. Management options include: avoid nitrogen application when the disease is active, avoid infrequent irrigation and allow the foliage to dry, mow when grass is dry, ensure proper soil pH, thatch reduction, and improve soil drainage.


Brown patch on tall fescue (Photos Alfredo Martinez)

For more information on Brown patch and Pythium visit http://extension.uga.edu/publications/detail.html?number=B1233

 

Gray Leaf Spot

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By Alfredo Martinez

Gray Leaf Spot


Figure 1 (left) and 2 (right). Gray leaf spot on St. Augustinegrass (images by Alfredo Martinez)

Gray leaf spot (Figure 2) is a fungal disease that affects St. Augustinegrass, perennial ryegrass and tall fescue in Georgia. The disease is particularly aggressive in St Augustinegrass. Hot, humid summer weather and high nitrogen levels can make turf susceptible to this disease. The fungus causing the disease is Pyricularia grisea.

Symptoms: The symptoms of gray leaf spot vary depending on the grass cultivar. On St. Augustinegrass, gray leaf spot first appears as small, brown spots on the leaves and stems. The spots quickly enlarge to approximately ¼ inch in length and become bluish-gray and oval or elongated in shape. The mature lesions are tan to gray and have depressed centers with irregular margins that are purple to brown. A yellow border on the lesions can also occur. In cool-season turfgrass, the symptoms are similar to those of melting out.

Conditions Favoring Disease: Gray leaf spot is favored by daytime temperatures between 80ºF to 90ºF and night temperatures above 65ºF. It is also found in areas with high nitrogen levels and that are stressed by various factors, including drought and soil compaction. This disease is most severe during extended hot, rainy and humid periods.

Disease Management Tips: Management practices that minimize stress and avoid rapid flushes of lush growth during the rainy season lessen the likelihood that severe gray leaf spot symptoms will develop. If irrigation is used to supplement inadequate rainfall, water infrequently but deeply.

Proper irrigation regimens should protect against symptoms of drought stress without increasing disease pressure by extending periods of leaf wetness. Excessive soil moisture and leaf wetness promote gray leaf spot. Irrigating in the late afternoon or evening should be avoided, as this prolongs periods of leaf wetness.

Proper mowing practices are most important for gray leaf spot management in St. Augustinegrass. This grass must frequently be mowed during the summer months to remove excess leaf tissue and keep the canopy open and dry. Mow the turf at the correct height for the designated turfgrass species and remove only one-third of the leaf blade per mowing. Collecting clippings reduces the spread of the disease when gray leaf spot symptoms are evident. Thatch layers should be removed if they are greater than 1 inch in depth.

St. Augustinegrass is especially sensitive to some herbicides. If possible, manage weeds using cultural management techniques and minimal amounts of herbicides. The timing of any atrazine application should be chosen carefully, as this herbicide can stress the grass, especially when temperatures may climb above 85 degrees F. Atrazine applications made before or during disease-favorable conditions increase the likelihood of severe gray leaf spot symptom development. Spot-treating trouble areas with the herbicide may also be considered. Herbicides should always be applied according to the label instruction

Fungicides are available to control the disease. Consult the current Georgia Pest Management Handbook — www.ent.uga.edu/pmh/.

Flea Beetles in the Garden

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I have seen several outbreaks of flea beetles on eggplant as I visit community gardens around Georgia this summer. Their damage is easy to identify as leaves become skeletonized due to the feeding of adult flea beetles.

If the eggplants are mature, the damage can be tolerated by the plant and you should be able to have a fine eggplant crop. If the infestation is severe or the flea beetles have found young, small plants the beetles can severely damage the plant and cause a reduced yield.

Close up of a flea beetle on an eggplant leaf.

You will notice the small beetles will jump if they are startled, which is how they came to be called flea beetles. Female beetles will lay eggs around the plant. Emerging larvae will head into the soil and could possible feed on plant roots. The mature beetle will emerge to feed on your plant leaves. The insects overwinter as adults in plant debris and litter in the top of the soil. There will be more than one generation per year.

There are chemical controls available and you should contact your local UGA Cooperative Extension office for recommendations. After your eggplants are finished definitely remove all plant debris from the soil bed. I would caution in planting collards or any other leafy green in that same soil this fall. Since you are growing leafy greens for the leaves, you will want to avoid flea beetle damage. Any larvae left in the soil after your remove eggplant debris could emerge to find your greens a tasty meal.

Happy Gardening!

A New Exotic Tick is Headed to Georgia

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by Nancy C. Hinkle, Ph.D.
Dept. of Entomology, Univ. of Georgia, Athens

Anyone who has lived in Georgia probably has experienced ticks, either on themselves or on their pets. The most common of the state’s 22 native tick species is the lone star tick. The American dog tick is the next most frequently encountered tick; even though it is called a dog tick, it can be found on mid-sized wildlife of all types – coyotes, foxes, raccoons, opossums, etc. Gulf Coast ticks seem to be increasing in prevalence and expanding their range. Deer ticks are not very common (the ticks typically found on deer are lone star ticks).

But there is a chance that we’ll be getting a new type of tick – as if we needed it. Last year a tick species that had never been found in North America showed up on a farm in New Jersey. Despite control efforts and a harsh winter, it successfully overwintered and in 2018 has already been found in Virginia, West Virginia, Arkansas, and North Carolina. Its mode of distribution is unknown, but this rapid spread bodes poorly for containment.

Originally from northeast Asia, this tick showed up in Australia and New Zealand over 100 years ago, where it has established and become a significant problem on cattle and sheep. Known as the “Longhorned Tick” (scientific name Haemaphysalis longicornis), it is capable of transmitting several disease organisms infecting livestock and humans.

Why is this tick of particular concern?

  1. It is not native to North America. That means there are no natural controls here to keep it in check – no predators or parasites to suppress its numbers. Also, our animals have not developed any natural resistance to it, so it is anticipated to thrive on both wildlife and livestock.
  2. Males are extraneous. This tick is parthenogenetic, meaning females reproduce without mating, so males are unnecessary. Of course, this means that a single female transmitted into a new area can start a new population, indicating that infestations can readily spread. And each female produces over 2,000 eggs, so populations can rapidly explode.
  3. Longhorned Ticks do well on a variety of hosts, wildlife as well as livestock. They should thrive on white-tailed deer and quickly spread to livestock. They readily feed on small ruminants, horses, dogs, cats, humans, and several common wildlife species.
  4. This tick is tolerant of a wide range of environmental conditions, but will flourish in the Southeast, which has climate similar to its native range. As has been shown, it successfully overwinters in New Jersey, Virginia and West Virginia, so may well be active year-round in Georgia.
  5. The Longhorned Tick is capable of transmitting several animal and human pathogens. Large numbers of ticks feeding on an animal can produce anemia, particularly in young animals.

Unfortunately this invader looks like many of our native ticks, small and brown before it feeds, then swollen and gray after it takes a blood meal. So what should Georgians be looking for to alert them to the Longhorned Tick? High numbers of ticks per animal. Because each tick can produce over 2,000 eggs, tick populations expand rapidly and frequently exceed hundreds per animal. If you find an animal with lots of ticks on it, pull off at least a dozen, put them in a small bottle with alcohol, and take them to your county Extension office. Tell them to send them to Dr. Hinkle in Athens and we will identify them for you (be sure to include your contact information). Then treat the animals to kill the remaining ticks (consult the Georgia Pest Management Handbook for recommendations on tick control).

We may not see Longhorned Ticks in Georgia any time soon, but we do not want to miss them if they do show up.

A Country of Gardening Immigrants

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Happy 4th of July week!   I hope your celebration will a good one full of fresh Georgia tomatoes, onions, watermelons….

As we think about the birthday of our country and how Americans celebrate there is always some type of food involved.  And, depending on your cultural background it could include extra garlic, long beans, or tomatillos.  The world is our garden and we have always been a country of immigrants.

A County of Gardening Immigrants
Chinese Long Beans

A Garden is Common Ground

Across our country experienced gardeners are welcoming immigrants and refugees from all over to the United States in a garden setting.  A garden is common ground.  There may be language barriers but we can all “talk” seed, soil, and water.

Having the privledge of working with some of these gardens it is exciting as cultures are shared through the growing of food.  Gardeners from Somalia are interested to see what the gardeners from Burma are growing.  Gardeners from Kenya are poking their heads in the Syrian’s garden to see what is coming up there.  Our American melting pot is alive and well in the garden.

People especially seem to enjoy growing foods from their homeland and their childhood.  This is true even within the United States.  Many a displaced Southerner has taken the family collard green seeds when being transferred to “the North”.  Year after year, I grow family bean seeds brought down from the hills of Kentucky to Georgia.  So, it is to be expected that our collective palate would be enriched by foods brought with immigrants from other countries.

A Diverse Dinner Plate

If you are fortunate enough to be invited to a pot-luck dinner at one of these gardens, it is an experience worthy of a 5-star restaurant rating.  And, it will make you truly thankful for our county and all of its diversity.

A County of Gardening Immigrants
North Fulton Extension Garden

A special “Thank You” goes out to a local food partner Global Growers who does such tremendous work with these gardeners in Georgia.  And to gardens like the International Garden of Many Colors in California, the Fresh International Garden in Anchorage, Alaska and the North Fulton Extension Garden in Sandy Springs, Georgia.

Happy Birthday, America!