One of the major battles of summer is keeping damaging turf pests at bay. The damage they cause is easily misidentified as drought stress, and many of the pests are difficult to control. For these reasons, it is often weeks to months before the perpetrator of the ever-expanding brown spots is found. 

 

Be proactive in observing brown spots, as this helps identify potential problems more quickly, and diligently maintain lawn health. Healthy lawns are less attractive to pests and they also recover more quickly from infestations. Conversely, grass that is fertilized and irrigated excessively is more attractive and has reduced ability to overcome infestations. Consider this information on lawn pest management.

 

• In northern Utah, there are three common turf pests: various species of sod web worm, bill bugs and white grubs. When damage is first noticeable, it is often as general thinning and browning of turf in limited areas. Over time, the brown spots expand where visible damage often peaks in late summer or early fall.

 

• Of these pests, sod web worms are the most common. Most sod web worms feed on grass blades and crowns as caterpillars. A separate species called subterranean sod web worm or cranberry girdler causes more severe damage by feeding not only on crowns but also on roots. An indication of infestation of sod web worm is small moths, off-white in color, flying in the lawn on summer evenings. They are especially active when disturbed. 

 

• White grub and bill bug larvae feed on crowns and roots also. Their larvae are white in color, c-shaped and often have a brown tented head. White grub larvae also have leg-like appendages on their front section.

 

• To differentiate insect damage from drought stress, try pulling gently but firmly on the brown turf. Pest-damaged turf often comes up easily, with few to no roots attached. Grass damaged by white grubs, bill bug and subterranean sod web worm will often pull back like a rug, and larvae are often found under the removed turf. Unfortunately, damage often requires days to weeks to appear and, once it does show, pests are then feeding in adjacent green turf. 

 

• In situations where damage is severe or has occurred for many years, use of preventative pesticides is a good option. Two common products include imidicloprid (Merit) and halofenozide (Mach 2). A second preventative application may be needed in late summer to prevent fall feeding damage from subterranean sod web worm. There are also products such as carbaryl (sevin) and trichlofon (dylox) available that control pests if a preventative application was missed. However, these are often less effective because pests are harder to kill when they are more mature, and the damage is often already severe.

 

• Once insects are controlled, lawns that have had severe problems often require re-seeding or re-sodding. Otherwise, maintain turf with correct fertilizing and irrigation and it will recover on its own. For basic tips on maintaining a healthy lawn, visit:https://extension.usu.edu/yardandgarden/lawns/.