Xtremehorticulture

Lawn Diseases Struggle When the Humidity is Higher than Normal

Q. I live in Henderson where we enjoy having a lawn as part of our yard. It was thick and beautiful when we moved in, but it soon withered after we made some changes to sprinkler layouts and had the water off for awhile. I laid fresh sod and it too struggled. I tried a fungicide and that seemed to help but it then died completely.  Now the rest of the lawn is headed in the same direction. I’m at the point of desperation and could use some sound advice in the midst of some differing opinions. This is the lawn the reader talked about. It is dying in patches. The reader asked me to look at it (consult) but I think the disease problems we had (high humidity) earlier had a lot to do with it. A. Outside of watering, some lawns experienced disease problems earlier in the season that lingered after we had high humidity due to the rain. That change in our weather encouraged plant diseases to occur. In the desert, it’s usually the higher humidity that’s the problem. I will take a look at this lawn and see if the disease is advancing or has stayed put. That will tell me what his options are. Now he must stop the lawn disease (if advancing) and get the grass to come back. The humidity is now below 15% (except directly above lawns) and lawns should not need a fungicide application to keep the disease from spreading if we allow the lawn to dry after we apply water, and it is in good health. When there was higher humidity, some lawns along with some other plants, may have needed a fungicide. A lot of it had to do with the lawns current health. If you applied a lawn fungicide, it should have stopped needing the applications if the general humidity was above let’s say 25%. Plant disease susceptibility is sometimes compared to a three-legged stool. Plants are susceptible to fungal disease if: 1. the disease organism is present, 2. general health and susceptibility of the plant is good, and 3. the current weather. In this case, all diseases like moisture. A couple of months ago the weather (humidity) was the problem. The higher humidity is now over. The relative humidity is now in the “desert” range. I think you are seeing old lawn disease damage (unless the lawn grasses are in poor health). Make sure you follow label directions when you apply any fungicide. Any traditional broad-spectrum fungicide should work, but generally the higher-priced fungicides for lawns are usually a better choice in that respect. This fall we should be watering lawns about two to three times each week. No more than four times each week for sure! Water early in the morning (imperative) and wet the lawns from 8 to 10 inches deep in a single application when you water. Sloped areas, or hard soils, may need multiple starts, about 30 minutes to one hour apart, to keep the water from “puddling” into low spots.             Your lawn may not need it but try “aerifying” your lawn with a gasoline driven core aerifier. Then “topdress” your lawn with a rich compost to fill the aerification holes. Irrigate your lawn immediately after this. This process of filling the aerification holes, followed by topdressing and irrigation, improves the rooting depth of the grass. This will improve a lawns (grass) health.

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Desert Green Presentation on Fruit Tree Pest Update for 2013

Fruit Tree Pest Update 2013 Notes for the PowerPoint presentation Robert Ll. Morris University of Nevada, Emeritus Desert Green is a conference held each year in Las Vegas for landscaping industry professionals. Here is a summary of my presentation on PowerPoint and my notes for my presentation. Slide 2.The UNCE Orchard was established in 1996 in North Las Vegas at UNLV’s Center for Urban Horticulture and Water Conservation. The center is located 100 yards east of the intersection of North Decatur and Horse Drive. Visiting hours are every Tuesday and Saturday morning from 8 AM until noon. Volunteers at the Orchard are welcome. The Orchard was established as a research and demonstration facility through Cooperative Extension. Slide 3. Fruit growing can be very successful in the desert because of our isolation from commercial orchards, our low humidity which helps to suppress diseases, and our high light intensities which helps to produce high levels of sugar in the fruit. Much of our plant material comes from Dave Wilson Nursery in northern California which produces high quality fruit trees for commercial orchards and nurseries. All of the fruit trees are planted by bare root, usually in late January or early February. We produce our own compost using local horse manure and green waste. The facility is a distribution center for wood mulch which is recycled urban green waste, primarily chipped trees removed from urban landscapes diverted from being buried at our local landfills. Our principal supplier of green waste is First Choice Tree Service, a Las Vegas based company. The management of the Orchard is focused on none or reduced pesticide applications, integrated pest management and ET-based irrigations. Slide 4. Whitewash reduces borer damage. We use whitewash painted to the outside of our trees to reduce sunburn damage. Sunburn damage to the trunk and limbs can attract boring insects such as the flatheaded Apple tree borer and the Pacific flatheaded borer which are problem insects in Las Vegas landscapes. By spraying the trunk and limbs with whitewash we can reduce the surface temperature of the trunk and tree limbs by five or 6°F. Whitewash is made by diluting white latex paint, or off-white latex paint, with an equal amount of water. In some cases more water can be used but the resulting whitewash should leave the trunk and limbs white in color. The most important sides of the trunk and limbs are West and South facing as well as the top sides of limbs. These areas receive the most direct and intense sunlight and usually show the most damage from boring insects. The whitewash will need to be re-sprayed or renewed every 3 to 4 years. Slide 5. Compost at planting enhances growth. This planting is nopal cactus which is used in Mexican culture as fresh vegetable, the fruit and animal fodder (feed). Once a pad is planted in good soil, harvesting of fresh vegetable from young pads can occur the following year. In three years, cactus fruits are ready to harvest. Cactus pads were planted in 2006 on the right side of the picture using compost applied to the soil after planting. The following year, 2007, pads were planted on the left side of the picture by this time the same amount of compost was mixed with the planting soil. Irrigations were every three weeks during the summer. Fertilizer applications were identical. Cactus pads that were planted with compost mixed in the soil exceeded the growth and production of cactus planted with compost applied to the surface only. In our desert soils it is very important to properly command soil at the time of planting for good growth, even of cactus. Slide 6. Staking equals faster establishment. It is important to stake newly planted trees to immobilize the roots so the tree can become established more quickly. If trees are not staked properly and the roots are not immobilized, movement of the plant due to wind can cause slower establishment. As trees begin to leaf out in the spring their canopy acts like a sail and can catch the wind causing the trunk to bend and possibly moving the root ball. Stakes should be driven into solid soil beneath the planting hole and not just the loose soil used for backfill. Trees should be tied to the stake so that the roots are immobilized but allowing the canopy and upper trunk to move. If the stake is not driven into solid soil, the root ball can move and root damage can occur with us slowing establishment. Slide 7. Wood mulch improves tree growth and health. Applying wood mulch to the soil surface has many benefits. Mulches help to keep the soil cool, moist, suppress weeds, improve soil quality, provide nutrients as it decomposes, fosters animal decomposers such as earthworms, lower soil pH and other benefits. Many plants in the landscape prefer to grow in improved soils rather than raw desert soil. Improved soils contribute to improved plant health. The best wood mulches come from a mixture of different types of trees. Bark mulch is pretty to look at but does not break down easily and contribute to the improvement of the soil and plants. Bark mulches easily blow in light winds and move in surface water. Wood mulch that has been chipped from trees does not blow easily in the wind and interlocks because of its rough surfaces. Wood mulches should be applied to a depth of 4 to 6 inches. These mulches should be kept away from the trunks of young trees, a distance of about 12 inches, until these trees are at least five years old. Wood mulches can be created from chipped landscape trees removed from local urban landscapes. When this wood has been chipped it will not contribute any disease or insect problems to landscapes where it is applied. Slide 8. Wood mulches were applied to fruit trees immediately after planting and the growth of these trees was compared to trees that did not receive any

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