|
|
Alert: June 20, 2006 |
|
Fairy Rings in Turfgrass My job is interfering with my ambitions to get in better shape. Any
time I go out for a run, walk, or bike ride I seem to get distracted by
the plant diseases in my neighborhood, like the two “fairy rings” I
stopped to look at this weekend. (Maybe it’s just an excuse to catch my
breath on a hot day!) |
Anyway, the magical sounding name comes from old stories where people thought that the rings of mushrooms were caused by dancing fairies. Fairy ring fungi can emerge quickly. The fungi develop pre-formed mushrooms as egg-shaped structures just below the soil surface, with all the cells intact and ready to go. When weather is favorable (warm and wet) these pre-formed structures expand and pop out overnight. Fairy rings are most obvious in turfgrass but you can also sometimes find them in forests.
|
|
Fairy rings are caused by many species of fungi. The fungi start in a small zone and grow outward. The rings can expand radially up to a foot or two each year. The fungi release nitrogen at the leading edge of growth, and that is why you see the flush of dark, green turf. Some fungi produce chemicals toxic to plants, and the fungi can also interfere with water absorption by the turf roots. Those factors can interact to give a ring of dead turf. |
|
Some mushrooms or puffballs (in type 3 fairy rings) are poisonous, so if you have kids or pets around that tend to eat anything in sight it is a good idea to destroy them—just mow or rake them over so your toddlers don’t see them and get curious. Wash your hands if you handle the mushrooms. If they bother you, the
rings of dark green turf can be disguised by fertilizing the rest of the
lawn to make the color more even. Rings of dead turf are harder to manage.
There aren’t many chemical options available for homeowners, and it is
probably easiest to let the ring run its course. For commercial turf,
Bayleton (triadimefon), Prostar (flutolanil), and Heritage (azoxystrobin)
are some chemicals that help manage fairy ring when used in conjunction with
good aerification and thatch management. Using surfactants and watering the
chemicals in can also increase efficacy.
|
|
|
Managing Tomato Leaf Spots in the Home Garden Early blight (caused by Alternaria) and Septoria leaf spot are two tomato diseases that tend to pop up in June. Both of the disease-causing fungi survive the winter on infected plant debris, and they can also be introduced on infected transplants and seeds. These fungi tend to get established on the lower, inner leaves first. Septoria leaf spot is characterized by abundant small (about 1/8 inch), grey, circular spots with dark borders. Sometimes you can see little black dots in the lesions. Early blight causes larger lesions that are dark brown or grey with many concentric, darker rings (like a target). The two diseases can both occur on the same plant, and both can cause defoliation which weakens the plant and decreases fruit quantity and quality. Both pathogens are favored by wet conditions. The first step in managing these leaf spots is to stake or cage plants to promote good air movement and prevent high humidity and leaf wetness. Control weeds to further improve air flow. Placing straw mulch around the plants can also reduce pathogen spread by reducing splash dispersal. Try to avoid watering late in the day (which increases the dew period) and avoid watering the foliage—direct the water onto the ground and avoid splash. During the season pull out any infected leaves. Be sure to check the leaves at the bottom and interior of the plants where the pathogens might be hiding. At the end of the season try to clean up any old, infected debris. There are chemical control options that can be useful if you have a history of leaf spots. Check out the home garden products at your local garden store. Chemicals that are labeled include chlorothalonil, maneb, and copper compounds but there are more. Read the label carefully. Start applications early. It is nearly impossible to regain control by the time you see a lot of lesions. [Kennelly]
Cold Weather Crown Stress Now Evident in Many Corn Fields Several weeks ago I alerted you to the potential for an environmental problem we have named cold weather crown stress (see Alert #06-03). In the past two weeks, as the weather has heated up and the soils have dried out, several samples exhibiting symptoms of this problem have arrived in the diagnostic clinic. Externally, plants are stunted and most frequently show signs of potash or zinc deficiency. Splitting the crown will reveal various levels of crown decay, depending on the severity of the problem. Keep in mind this damage was initiated in early May but is just now becoming visible. Some plants will not survive due to drought stress or being shaded out by taller, neighboring plants. Others will recover, but will be more susceptible to stalk rot later in the summer. (Jardine)
Scout Now for Corn Foliar Diseases Mid-June marks the time of year when more active scouting for foliar diseases in corn should begin. In Kansas, gray leaf spot, anthracnose and northern corn leaf blight are the most common diseases. All of the diseases usually begin on the lowest leaves and move upward. No-till, continuous corn is most vulnerable, but disease levels in no-till corn rotated with soybeans in a two year rotation can also be high. Symptoms of the diseases are: Gray leaf spot – initial lesions are small and irregularly shaped. A yellow halo is usually observed when the leaf is held up to the light. As the lesion matures, it becomes rectangular (1/4 to 2inches long with the width defined by the veins). The lesion can be tan to gray in color, depending on humidity levels. Anthracnose – these are small, irregularly shaped, tan lesions with red, reddish brown or yellow orange borders. Lesions may coalesce and the entire leaf may become blighted. Northern corn leaf blight – this disease is characterized by large elliptical or cigar-shaped lesions that can be 1 to 6 inches in length. In Kansas, fungicides are often used to control gray leaf spot. See KSU Extension Bulletin MF-2341, Gray Leaf Spot of Corn for threshold levels and management recommendations. (Jardine)
Plant Disease Highlights June 12-16
Heat stress/scorch (Hot windy weather) - On
lots of stuff.
Contributing Author(s) Megan Kennelly
kennelly@ksu.edu
|
|
Web updated 9/01/06 |
