There are a handful of pests that will seek to destroy your lush, beautiful lawn – even in the Pacific Northwest. Below, we have isolated the most common and provided our recommendations for treating them.
White Grubs (Masked Chafer Beetles, June Bugs, Japanese Beetles)
The larvae of the different types of scarab beetles can be found in your lawn. As the grubs feed on the roots of the grass, the blades wither and eventually die. Aside from noticing that there are large numbers of beetles in your yard in the spring and brown patches of grass in the late summer, there are a few other tell-tale signs that the brown patches in your lawn have been caused by grubs.
- You notice skunks or raccoons digging up parts of your grass. These animals love to feed on the mature grubs before they cocoon and they will dig up the lawn to get at them.
- The brown patches in the grass easily peel back from the soil when pulled. Grubs will feed on the grass roots that hold the turf to the soil.
If you suspect you have grubs, pull up a one or more square foot sections of the grass and visually inspect for large, white worm like insects. Small infestations may not result in permanent damage to your lawn and therefore may not need to be treated. But if you see multiple grubs in small areas, it may be time for treatment.
Beetles lay their eggs in the lawn in mid-summer. The larvae then hatch and begin to feed on the roots of your lawn until the fall when they move to deeper soil to survive the colder winter months before emerging again in the spring to feed again.
The best time to treat for grubs is before they hatch. In spring or early summer, you can apply a grub preventative control product to your lawn to kill the eggs and younger larvae. However, there are insecticides which treat grubs in later life cycle stages such as the white grub stage described above. Check with your garden center for the type of product that best suits your situation and the time of year. Make sure to follow all instructions on the package and water your lawn thoroughly after applying any insecticide.
Gophers & Moles
Both of these furry burrowing invaders can cause severe damage to your lawn by digging holes or tunnels. While gophers may often be visible poking a head out of a hole, you’re not likely to ever see the nocturnal mole in your grass. There are a number of humane ways to control mole and gopher populations including trapping; placing strong smelling or bad tasting items near tunnel entrances; or annoying them with noise making devices. Your local home improvement store can provide you with a variety of traps or repellants. Another option is to consult your local pest control specialist.
Cutworms or Webworms
Sod webworms and cutworms are “lawn moths” which lay their eggs before the winter then the worms or larvae emerge in the spring as the weather warms. The worms feed on grass blades at night using a small tunnel in the turf to carry the leaf blades into the tunnel. Silken threads can be seed in the early morning covering the tunnel of the sod webworm. Often the damage to the leaf blades can be extensive enough to leave brown patches in the grass. Like the webworms, cutworms also feed on the grass plants after hatching in the early spring.
There are a couple of ways to identify cutworms in your grass. One would be to pour some very soapy water in a patch of the affected grass and watch for 10 or 15 minutes to see if the worms emerge from the soil. Another method would be to thoroughly inspect brown patches of your lawn at night.
The good news for homeowners is that birds will often decimate as much as 90% of the larvae population of both webworms and cut worms. However, infestations that are a larger problem may require specific insecticides. Check with your garden center for product recommendations and be sure to follow the package instructions. Be sure to de-thatch your lawn on a regular basis to prevent infestations from recurring.
Crane fly larvae feed on the roots and blades of grass all throughout the winter. Infestations are most often characterized by a thinning of the grass plants during spring when new shoots should be thriving. Additionally, starlings or robins may also destroy thinning areas of the grass searching for the grubs.
Monitor your turfgrass in early December for thin patches in the grass. Most larvae are found in the top 1 inch of soil, so sampling the soil can confirm the presence. Increased bird populations in the yard are also a sign of infestation.
Some studies conducted have suggested that “drought stress” has been effective in reducing the larvae population of the crane fly. Reducing or cutting out irrigation after Labor Day can often induce the level of “drought stress” needed for effective control. However, fall is also the best time of year to re-seed or replant areas of the turf that have been affected by other conditions.
In some cases, insecticides may be necessary to control larger infestations. Insecticides that are the most effective against the crane fly are also toxic to bees and other pollinators. With many insecticides, pets and children should not be allowed on areas that have been treated until the turfgrass has been thoroughly watered to soak the insecticide into the soil. Contact your local garden center for more specific instructions.