GARDENING: Many turf diseases a management problem

We still are receiving many calls concerning turfgrass "diseases" this year. Some of these are real diseases and others are management problems. I would strongly urge anyone with a lawn not to apply water to their lawns in short waterings, particularly at night, unless they need to prevent runoff into the streets.

First of all short duration watering encourages turfgrass diseases. Turfgrass diseases will run rampant whenever stressed, warm turfgrass is kept wet. This is a plain, simple truth for any plant.

Secondly, most turfgrass diseases favor wet conditions. Frequent short waterings at night keep the turfgrass environment wet and never give it a chance to dry out. This is very favorable for disease development. Diseases like warm, humid places to grow. Your turfgrass lawn is like a pygmy jungle. The air above the grass where weather instruments are located may be dry but the air inside that "pygmy jungle" is as humid as any tropical rainforest after a rain.

Thirdly, short irrigation cycles waste water. As any farmer knows, when water is applied in short cycles there is more water lost due to evaporation.

What is the answer then? We must go back to the old fashioned basics of watering your lawn. Water the lawn long enough to water the entire root zone. On some lawns this may be to a depth of 12 inches. On others this may be only two- or three-inch depths. The only way to know is to stick a long screwdriver in the lawn in several places and see how far it can penetrate. The roots can go this deep as well if the lawn in managed properly.

Timing may vary from 10 or 12 minutes for spray heads to double that for sprinklers that rotate. Try to do the entire irrigation in one application if you can. If you do get runoff or puddling then split it into two or three applications in succession, no more than half an hour apart.

Water during the early morning hours. Avoid nighttime applications. The lawn should never spend the entire night wet.

If the disease seems to be spreading slowly or hardly at all then avoid applying a fungicide. It is my recommendation that if you are relatively certain that you have a disease problem on your lawn and it appears to be actively spreading, then make an application of a broad-spectrum fungicide to contain the disease. Do this according to the label only.

Remember that these products are poisons and have associated health risks. Some of the health risks are noted on the bag or label with the words "Caution," "Warning" and "Danger." Read the label to learn of some of these associated health risks.

If at all possible, avoid the application of pesticides unless it is warranted. If the disease problem is not spreading rapidly, try changing some of your management practices instead of applying a fungicide. Increase or decrease your mowing height, irrigate at a different time or cut back on fertilizers.

Other possible causes of brown spots? Our No. 1 reason for brown spots is irrigation. In the spring we often get caught off guard when hot dry weather is upon us. This year in particular, hot weather was delayed and then came on very quickly with dry winds.

Brown spots due to a lack of water can be distinguished from other types of brown spots usually because the leaf tips die back in the affected area. If it's severe, the tips or blades may die back all the way to the soil. However, when the brown leaf blades are peeled back exposing the inner stem, the stem is succulent and healthy. When plenty of water and fertilizer is resupplied, the healthy stems will explode with new leaves in a matter of one or two weeks.

Question: I have two pear trees -- one Bartlett and one Asian -- situated side by side in a raised planter box. The trees are about three years in the ground from 15 gallon size. Both trees are doing well, although the Asian is doing better. Both are producing fruit. My problem is, the fruit doesn't seem to ripen, or at least I'm not sure when to pick. I've pulled fruit several times but it always tastes bitter like they're green. The greenish hue on the fruit that is usually there has begun to turn to a brown husk on both varieties. When do pears usually ripen in this region?

Answer: Pears should never be allowed to ripen on the tree. Those that do may develop grittiness or will be subject to browning around the core and internal breakdown. The area around the core turns brown and mushy. Pears ripen best off the tree.

Commercial growers use a pressure tester to determine proper pear maturity for harvest. By determining the pressure necessary to puncture the flesh, they can determine when pears are ripe enough to pick, but not overripe. We are picking Bartlett at our orchard in North Las Vegas sometime in late August to September. It differs year to year.

Q: Quite an unusual situation in my oleanders: lots of pods. Is this a normal happening? I've had the plants for eight years, but I never noticed such an abundance of "string bean" like buds. Should I worry?

A: I would not be overly concerned. Oleanders are very tough to harm. It is hard to say why they have so many pods compared to other years. It could be just a favorable year for seed production. Some plants will have good years for setting seed and bad years. It could be stress. Sometimes plants under stress will set more seed than when they are happy.

Why is it stressed? It could be a lack of water or even too much water. I would be watering no less than once a week and probably no more than three times a week depending on the soil. I would water it deep and not shallow. On drip, water until it reaches a depth of at least a foot. Better if it reaches two feet. These are not low water use plants. They are high water users but can withstand drought exceptionally well and are tolerant of most desert soils. Signs of water stress are poor growth, scorched leaves and stunting.

There isn't too much else that bothers them. Oleanders have very few disease problems and very few insects that harm it except for the yellow oleander aphid and some scale insects which don't really hurt it that much.

Q: I read your story about the rabbits. I have had some success by using mothballs. They only seem to come into my back yard which is open except for some bushes. So I spread the mothballs along the bush line and it works pretty good. Hope this works for you.

A: Thanks for your suggestion. Readers?

Q: My neighbor has a date palm tree. It drops the seeds all over the ground. Are these "dates" edible? Looks like some of them have been munched upon I am guessing by birds or those little chipmunks.

A: Yes they are edible. It is only a question of whether you would want to eat them. All palm seeds, to my knowledge, are edible. Date palms begin to bear fruit at 3 to 5 years, and are fully mature at 12 years.

Some date facts. There are 600 different kinds of domesticated dates worldwide with 60 percent of the world's production coming from mostly Arab countries. The fruit of the date has one seed, which can vary in size, shape, color and quality of flesh. Unripe dates are green in color, maturing to yellow, then reddish-brown when fully ripe. Dry or bread dates are self-curing on the tree. Soft dates require harvest at appropriate time and sun-drying to increase sugar content and prevent spoilage.

A single large bunch may contain more than a thousand dates, and can weigh nearly 20 pounds. Each tree can produce between five and 10 bunches. A mature female tree can produce upwards of 150 pounds of fruit annually. Wild dates are similar to domesticated dates but have smaller, inedible fruits.

There are many escapes from cultivation and hybrids between wild and domesticated dates, making a distinction between wild and domesticated populations is quite difficult.

Q: Last week I used Scott's Summer Guard on the lawn. The lawn is beginning to turn a light bright yellow? Did I burn it with the fertilizer? Normally the Summer Guard works great! What can I do to fix and get back to the nice green color?

A: It's possible you damaged the lawn if the fertilizer was applied a bit on the heavy side or if it was done when it was wet or in the direct heat of the day and not watered in. If the fertilizer caused it then I would try to keep the lawn as wet as possible and not let it dry out. As the soil begins to dry, the fertilizer salts will become more concentrated and increase the chances for damage to occur particularly during the summer heat.

Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.


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