Q. How can I tell what is wrong with my lawn? It has brown spots here and there, but I don’t know if those are from irrigation problems, insects or some disease.
Most lawn damage is caused by inadequate irrigation, dog urine, mowing too short, excessive pesticide or fertilizer use, or planting the wrong type of grass. Of course, pest insects can cause similar damage, but these causes should be ruled out before you reach for that bottle of insecticide.
Irrigation issues should be ruled out first, since these are usually simple to diagnose and fix. Sprinkler systems should be set up to provide head-to-head coverage, which ensures that all parts of the lawn are getting the same amount of water. Place similar-sized straight-sided containers (such as empty cat food or tuna cans) equally spaced all over the irrigated area and run the sprinklers through a complete cycle. Each can should contain equal amounts of water if the sprinkler system is operating correctly. If this is not the case, the system may need attention. Sprinkler heads may need to be re-aimed, cleaned, or replaced. Since we live in a dry climate, any area that is not getting enough water will quickly brown, so irrigation is essential for healthy turfgrass.
Dog urine spots should be flushed with plenty of water to dilute salts. Cut grass with the mower blade set to the highest level and mow more frequently. Grass that is too short is susceptible to heat or water stress as well as weed invasion. When fertilizing, less is more. Apply sparingly and, if needed, repeat treatment. Giving grass too much fertilizer at once can cause burning.
If you still suspect that insects are causing turf damage, it’s important to properly identify the pest before treating. Some common lawn pests include army worms, bill bugs, crane flies, sod webworm, southern chinch bugs, and white grubs. Refer to the U.C. Guide for Healthy Lawns for information on identifying and treating these pests.
Keep in mind that treating with insecticide should be a last resort, since these treatments will also kill beneficials that control the pest populations. Predatory beetles, rove beetles, predatory ants, springtails, and millipedes are only a few of the many types of beneficials that coexist with pest insects. If you kill off all of the insects in your lawn, the pests will return well before the beneficials have a chance to recover.
Los Angeles County
mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/
Orange County
ucceocmghotline@ucanr.edu; http://mgorange.ucanr.edu/
Riverside County
anrmgriverside@ucanr.edu; 951-955-0170; https://ucanr.edu/sites/RiversideMG/
San Bernardino County
mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu