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Garden Help Desk: Dry spots in lawn may be sprinkler coverage issue

By Usu Extension - | May 29, 2021
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When sprinkler heads spray a fine, billowing mist instead of coarser droplets, the water can be carried away on air currents or breezes instead of landing where it's needed.

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Missing sprinkler heads create geysers instead of putting water out onto the lawn. This wasted water adds to your water bill without adding any benefit to your lawn.

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Codling moth larvae hatch and then begin to tunnel their way through the apple skin toward the core where why can feed on the developing seeds.

This week we’re taking a look at another lawn watering problem — what can we do about dry spots in our lawns.

Not all dry spots are related to watering problems; disease, insect damage and wear and tear can all cause dry spots, but watering issues are a common cause. If you feel you’re already watering deeply and infrequently, but you see isolated dry spots in your lawns, don’t assume you should water more to green up those spots. Instead, check to see if your sprinklers are putting on water uniformly.

One easy, low-tech way to check for uniform sprinkler coverage is to go out onto the lawn about 2-4 hours after the sprinklers have run. Take a long screwdriver and push it into the lawn in areas where the turf looks green and healthy. Then push it into the lawn in areas where it looks dry. If you can’t push the screwdriver into the soil to the same depth with the same ease, then that part of the lawn probably isn’t getting as much water as the green parts of the lawn.

Another way to check for uniformity is to set out a grid of catch-cups, tuna cans, cat food cans or something similar in the problem zones of your lawn. If you’re using cans, you may need to set a small stone in each can to prevent them from tipping over while the sprinklers run. Whatever you use, the containers should be the same size and shape. Run your sprinklers for several minutes. After you’ve run the sprinklers, remove the stones and measure the depth of water in each can. If the cans in the problem area have less water, you’ll know you have a uniformity problem.

Thoroughly examine your sprinkler system to figure out why those spots aren’t getting as much water as the greener parts of the lawn. Run your sprinkler system and look for sprinklers that are tilted (even a slight tilt can create a dry spot), clogged, damaged, blocked, missing or using the wrong nozzle. Sometimes, you simply need to replace a nozzle with one that has a higher output or longer “throw.” Watching the sprinkler system run is when you’ll also see whether sprinklers pop up as far as they should and also are giving head-to-head coverage.

Another possibility when you are troubleshooting dry spots is that prevailing winds during the hours when you normally run your sprinklers are blowing water away from the lawn. Adjust your sprinklers to spray coarse droplets instead of a finer mist or shift your watering time in those areas so that the sprinklers run when it is less windy.

If everything seems to be working properly and you’ve checked to make sure the “dry” spots aren’t actually well-watered spots where turf diseases or insect problems are getting started, try adding a few more minutes to your watering cycles and wait for a few waterings before you try increasing the frequency.

How long should you water each zone? There is no set number of minutes for watering. It depends on your soil type, water pressure, sprinkler type, nozzle output, etc. As a general guide, rotor sprinklers (they pop up and then rotate or move a stream of water across the lawn) can take two or three times as long to put on the same amount of water as stationary pop-up sprinklers. It’s not that one kind is better than the other; it just means that they need to be managed differently.

Question: Is it time to start spraying my Golden delicious and Fuji apples to keep out the worms? How often should I spray once I start?

Answer: Probably. Codling moths have been active in some parts of Utah County for about 10-12 days and by Memorial Day this year, moths could be active and laying eggs in all areas of our county.

The spray frequency depends on the product you choose. Some products need to be repeated every five to seven days and others are effective for up to 17 days. Being diligent and spraying on the right schedule is more important than what you choose to use. If you do nothing, you could lose most of your apples. The more consistent you are, the more apples you’ll get to keep.

Also make sure you get good coverage each time you spray.

If you’re using up a spray product that is left over from last year, make sure it hasn’t been exposed to freezing temperatures or extremely high temperatures. If in doubt, purchase new spray for this season.


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