Faulty irrigation system can produce brown spots in lawn

A: I looked at your pictures, and the lawn looks good in most places except for a few small brown areas. Brown spots during summer months frequently point out weaknesses in the irrigation system.

My first suspicion is the irrigation system and was not installed or maintained properly. Let’s cover the basic “must dos” when installing and maintaining an irrigation system.

The operating water pressure must be within the operating range of the sprinkler nozzles. Frequently this is 15 to 30 psi. Some expensive sprinkler heads have built-in pressure regulators, but less expensive ones may not.

If the water pressure is too high, fogging or misting will occur out of the nozzle. If the sprinkler head is fogging, then brown spots will occur in weak areas. If the pressure is too high, reduce it with a pressure regulator.

Water must be thrown from the nozzle far enough to reach neighboring sprinkler heads. Sprinkler heads must be installed at distances specified by the nozzles. These distances are meaningless if you don’t have the right water pressure.

Sprinkler nozzles specify the operating pressure range, allowable spacing between sprinkler heads and precipitation rate in inches per hour, among other things. These nozzles must be matched to each other. If someone maintains the irrigation system and replaces a nozzle with the wrong kind, it will produce brown spots in underwatered, weak areas.

Curved areas and recurved areas of the lawn are the most difficult to water. There are adjustable nozzles that can be used, but it will always be a weak irrigation area subject to brown spots.

Never water early at night, like at 9 p.m. If your lawn is healthy and has a good irrigation system, one irrigation per day during summer is all that most lawns need if the sprinkler system was designed and installed correctly.

Irrigations should finish just before dawn. If you must water late in the day, apply water so that the grass leaf blades dry before it gets dark.

Don’t rake or catch the grass clippings when mowing. Most mowers now are “mulching mowers” with a special blade and deck design. Returning the clippings to the lawn substitutes for one fertilizer application each season.

Q: Unfortunately, it appears our kumquat trees may have bacterial blast fungus. Our tree appears very healthy and has given us a lot of fruit, but we recently noticed sap coming from the bottom of main branches. What treatment would you recommend?

A: I usually follow the KISS rules for diagnosing plant problems. Unless we are in a citrus production area or there is a history of disease on these trees, I first conclude it’s a man-made problem. Regardless, we must rule out the simplest reasons first before we jump to more exotic disease problems.

Root death because soils are kept too wet causes these symptoms on citrus. For this reason, I assume the trees watered too often or there is a water drainage problem in the soil surrounding the roots.

After the first year of growth, all fruit trees, including citrus, should be rooted firmly in the soil. A simple diagnostic tool helps to judge whether wet soils should be a concern or not.

Move the tree by its trunk, back and forth, while looking at where the tree enters the soil. The tree should be firmly anchored in the soil and not move it. If tree roots move the soil easily, then the soil has probably been kept too wet and the roots began drowning or rotting.

There is a tendency during hot weather to water fruit trees more often, even daily. Most fruit trees, including citrus, prefer at least one day of no watering between watering days.

Unless the tree is newly planted, or planted in sand, never water it daily. Instead, increase the minutes on the clock when you do water.

Anything that shades the surface of the soil during summer helps tree roots function better. Their primary functions regarding tree health are the uptake of minerals and water.

They do this better, however, if the surface of the soil is mulched. Wood chips (or even shredded cardboard, shredded newspaper or straw) lying on the soil surface gives fruit trees one extra day between waterings during the summer.

If the soil is not mulched or covered, soils dry quickly and get hot in our summer sun and heat. When soils are wet, tree roots grow where there is a good mix of air and water. Unless the soil has been amended quite a distance from the tree at the time of planting, most of the tiny roots that feed on water and nutrients grow in the top 6 inches of soil.

Q: My apple and apricot trees have small leaves and not much new growth. The few dark green leaves are almost dead. I fertilized the plant in the prescribed periods and watered the plant as in previous years. The apple tree made flowers but few fruits. The apricot had lots of apricots and dropped some earlier but few green leaves.

A: I think the problems are a combination of water, fertilizer and soil. As you know, the trees should be thick and dense this time of year. They are not because, I think, they lack these three ingredients.

Your trees are about 8 to 10 feet tall and would need about 20 to 30 gallons of water every other day this time of year. As trees get older and larger, they need more water. That works out to about 75 to 100 gallons each week.

There is a basin at the bottom of the tree that is maybe 3 feet in diameter. Increase the size of that basin to about 6 feet in diameter or 3 feet from the trunk in all directions. That will accommodate more water and spread it about a foot beyond the basin.

Spread about 1 cubic foot of good quality compost in the basin away from the trunk before you water it again. This compost should have a high nutrient content, such as Viragrow. Many do not.

After rebuilding the basin in a 6-foot diameter around the tree and applying compost, fill the basin with a hose or sprinkler on the end of a hose. Fill the basin twice.

Cover the soil in the basin with wood chips from local trees if you can find them. If you can’t find any, use straw 4 to 6 inches deep until you can find some wood chips.

Increase the amount of water to the tree by covering that soil with about 1 to 2 inches of water flooding the basin. Water the tree three or four times per week using this basin and flooding technique. You should see new growth starting in about seven to 10 days.

Q: I have a pomegranate tree that bears fruit with dark red seeds. I have been fighting a bug that turns the inside pale white, almost gray. I also have a big, slow flying bug that sits on the fruit and puts its tail in it, splitting it for the birds. We also have the katydids that I didn’t know were harmful until recently. I try to be as organic as possible.

A: Katydids are a problem on pomegranates in California, but I had never heard of it reported as a problem here. The picture you sent to me is not a katydid but a green lacewing, which is a “good guy.” Their young are probably after aphids or immature whiteflies.

I do not know what the second insect is, but be careful in identifying insects so you don’t confuse the “good guys” with the “bad guys.”

The leaf-footed plant bug is a perennial problem on pomegranates, other fruit and nut trees, and vegetables. Organic sprays such as soap and water are effective when they are very young but not so when they are older such as now. Control of these critters should start in about April.

Conventional pesticides such as synthetic pyrethrins are the only way I know of getting some control this time of year.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.