Lawn fungicide controls tall fescue disease

     By Bob Morris
     View columnist
      The following are typical issues our Master Gardeners deal with daily at the Nevada Cooperative Extension. If you have gardening questions, call the Master Gardeners' hot line at 257-5555 between 9 a.m. and 4 p.m. Monday through Friday. There is also a gardening Web site at http://www. intermind.net/mgarden/.
      The so-called summer monsoon season is overdue and some expect it to hit soon.
      Before it does, those who have had problems with diseases in tall fescue lawns during the summer months should keep a lawn fungicide handy to apply as soon as evidence appears that the disease is back.
      It's a perfect time for this disease to hit when air temperatures are above 100, accompanied by rain and high humidity and lush turfgrass growth.
      An indication of the disease is the occurrence of small patches of dead grass, often in the shape of a crescent or, later, a larger patch with a tuft of green grass in the center.
      Advanced stage of the disease is a large brown dead area with tufts of green grass spotted throughout it. The advanced stage occurs because the smaller dead spots enlarge and blend together, leaving the tufts of grass remaining.
      Remember, irrigations should be long and slow to get deep watering. Frequent shallow irrigations should be avoided unless it's on slopes to prevent runoff or on soils that are compacted.
      If soil is compacted, aerate the area. Lawn fertilizations should be avoided unless in very small quantities, except on Bermuda grass.
      n There is no reason you can't plant now, but avoid doing it in the heat of the day if possible. If this is not possible, keep containers out of direct sunlight, keep them well irrigated during the hottest times of day and get them in the ground as quickly as possible.
      Don't plant them in dry holes and do not lay sod on dry soil either. Laying sod on dry ground or planting in dry holes this time of year can result in severe dieback of the sod and containerized plants, and establishment time can be delayed several weeks or the sod or plants may be killed.
      Question: How come the leaves in my cottonwood trees are developing holes and scorching?
      Answer:It is very difficult for large trees to get enough water to the tops when we have this kind of weather. The taller the tree, the harder it is for that tree to get water to its peak.
      Therefore, leaf scorching often occurs on the sides of trees toward heat and the exposed sunlight and toward the tops. Make sure these trees are deep watered.
      Shallow lawn irrigations may not be enough for these trees even if they are sitting in a lawn. The holes are caused by the cottonwood shield bearer, but there really isn't anything practical you can do to control it and it shouldn't be a problem for the tree, provided the damage isn't extensive.
      We have a fact sheet available on the shield bearer from our office.
      Q: I'm having trouble with squash bugs. What's going on?
      A: Problems occurring now include squash bugs on squash and melons (we like to group these plants together and call them cucurbits), whiteflies on tomatoes, ant problems, the iridescent green fruit beetle, bird damage on fruit and vegetables not setting due to the heat.
      The two insects mentioned -- squash bugs and whiteflies -- are two of the hardest insects to control in home landscapes. In most cases when these insects are present in high numbers the most common recommendation is to destroy the plants rather than to try and control the insects. In smaller numbers and in early stages, chemical control is possible to some degree.
      These insects must be controlled early before they get established.
      Even though it is called the squash bug, this insect will attack all types of cucurbits, including zucchini, squashes and melons. Their feeding causes leaves to droop, turn black and dry out and can kill young plants.
      The adult squash bug is just over half an inch in length. Even though it's really brownish yellow, it looks black because it's covered with a layer of dense black hairs.
      From above, orange or orange and brown stripes will stick out from the side of the insect -- what we could call its "belly" or abdomen area. In the "neck" area, or pronotum, the edges are yellow. In May, June and July, look for shiny, elliptical reddish brown eggs laid in groups of 15 to 40 on the underside of leaves or on stems.
      Young insects called nymphs are pale green and feed in clusters sometime in late June or July. This is the stage when they are most vulnerable to insecticides, but it's also when damage is difficult to detect.
      Whenever you grow these plants you want to clean up the garden in the winter and compost plant debris. This reduces the insect's winter hiding places. Mulches applied at planting and removed at first bloom help to exclude squash bugs.
      There are no known organic methods of control except to use varieties less susceptible and keep the garden clean of debris. You can try applying insecticides such as sevin and diazinon labeled for vegetable gardens.
      Thiodan was the insecticide of choice in prior years, but this insecticide in now restricted in its use. Spray at dusk or when bees and other pollinators are not present.
      There are several types of whiteflies that cause serious problems to home gardeners; silverleaf whitefly and greenhouse whitefly may be the most common here.
      Plants that might show signs of damage in the home garden include vegetables in the cabbage family (broccoli and cauliflower), cucumber, squash, melons, tomatoes, eggplant, hibiscus, lantana, verbena, garden mum and Gerbera daisies.
      The silverleaf whitefly can cause problems such as leaves of squash turning a silver color (this is how it got its name) and the irregular ripening of tomatoes. Feeding on plants generally by whiteflies produces sticky honeydew on the leaves. A sooty, black mold may grow on the honeydew.
      Infested plants begin to dessicate like they aren't getting enough water, their leaves may scorch and the plant is off color and generally declines.
      Whitefly adults are tiny yellowish or white insects with white wings found mostly on the undersides of leaves.Whiteflies colonize the underside of leaves.
     
      Some native parasites such as tiny wasps, bigeyed bugs, green lacewing larvae and lady bird beetles -- which are also called ladybugs -- do attack it..
      One natural control product you can try is Neem oil but it's most effective on the younger insects. Soaps can be used but will need frequent applications.
      I can't emphasize enough the importance of keeping a clean garden in the winter and keeping the area weed free.
     Bob Morris is a horticulture specialist with Nevada Cooperative Extension.