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GARDENING: So many causes for turf problems; diagnosis is key

Curt Swift
CURT’S CORNER
Free Press Gardening Columnist
Courtesy photo
Staff Photo |

Many lawns are suffering from the heat, especially those with shallow roots due to improper watering or poor soil preparation. When the temperature increased to the point when the lawn was using more water than the roots could absorb, the grass blades were invaded by Ascochyta leaf blight and/or “dollar spot.” These two fungi cause the grass blades to turn white or straw-colored. This problem started with drought stress. Watering more frequently may not be the answer as this can increase the spread of these fungi.

Roots need to be deeper than 1 to 2 inches if they are going to absorb adequate water during our hot summer days. When roots are shallow due to watering every day, the amount of soil moisture available for the grass is limited. In other instances the problem is not due to shallow roots but the sprinklers are out of alignment or not adjusted properly. Some of the lawns I’ve looked at have sprinklers that need to be straightened; others need to be lifted so the nozzles protrude above the grass. In some cases a different nozzle needs to be used to ensure water is evenly distributed over the grass. All of these problems are easily seen if you turn on your system and observe the way the sprinklers work.

Dry spots between pop-up sprinklers are a common problem when one or more sprinklers are tilted. Sprinklers should be perpendicular to the lawn. Sometimes the problem is due to the nozzle not applying water to the close-in grass. Replacing the nozzle to a RainBird U-series nozzle often can correct these dry spots. These nozzles have an extra slit designed to provide water in close in areas. You might even have nozzles that don’t throw far enough. If you have 15 feet between nozzles yet you have a nozzle that only throws 10 feet you are going to have dry spots. The top of spray nozzles are marked with little tiny numbers indicating the distance they throw. Sometimes the sprinklers are too deep in the ground to extend above the grass and need to be lifted. It is a wise practice to turn each zone on once a week to check for problems so you can have them fixed.



Some of the lawns I’ve looked at have dry spots due to white grubs and billbugs. They eat the roots off your grass resulting in lack of water absorption. The blades of grass damaged by grubs and billbug may be attacked by fungus and inexperienced people may identify fungus as the problem. The fungus is a symptom not the cause of the spots.



CURLY TOP VIRUS

Growers in California have been plowing under their tomato fields. They have lost too many plants to a virus to make it profitable to even harvest. I’ve seen this same problem in local tomato patches and I know other gardeners have been having problems with this virus disease.

Last Sunday I was in Peach Tree True Value at the west end of North Avenue when a couple came in looking for the spray that will stop the leaves on her tomatoes from curling. What she most likely was seeing is a curly top virus-infected plant. Once the plant is infected, there is no cure and the plant will die. If the lady’s tomato plant stopped growing and turned yellow and the leaves developed purple veins and rolled over, her plant has curly top virus.

The California tomato fields were invaded by the beet leafhopper that carries this virus. They moved from drought-stricken areas into the tomato fields. This insect was feeding on weeds and native vegetation in the hills and when those weeds dried up the leafhoppers move to greener areas. While they don’t exactly like tomatoes, leafhoppers will land and probe with their needle-like mouth parts to see if the plant is good enough to feed on. If the leafhopper is harboring the virus when they probe, they inoculate the plant with the virus. This is similar to what happens when drug addicts share dirty needles.

This insect cannot overwinter outside in our area but the winds from the southwest bring them along to infect our tomatoes, beets, peppers, beans and many other vegetable crops. Every year when we experience a windy spring, you should expect problems with this insect and problems with curly top virus.

The tomatoes I planted are as susceptible to the virus as my neighbor’s tomato plants, but I cover my tomatoes with shade cloth, which also serves as an insect screen. The shade cloth also keeps the plants cool and consequently increases fruit set. If your tomatoes all die from curly top this year, keep in mind that shade cloth placed over the plants as soon as you put them in the ground and left on all summer except when you are harvesting will ensure a bountiful crop of tomatoes.

Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.


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