Lawn grubs, often referred to as grub worms, aren't actually worms at all. The majority of them are actually the larvae of the masked chafer and Japanese beetle. Around here in Carlsbad and Southeast New Mexico, these Japanese beetles that result from the grubs are often referred to as June Bugs. You may recognize them as the small brown beetles that start to show up in early to mid summer and fly around your porch light and accumulate everywhere.
Regardless of what type of critter they are, grubs can cause a lot of damage to lawns. The damage they create can be both directly from eating the roots of grass and plants and indirectly by attracting other animals like skunks and racoons that dig them up and eat them.
Identifying A Lawn Grub Problem
A problem with grubs in your lawn is usually visually obvious as it will create irregularly shaped yellow dead areas in the turf. However, yellow dead spots in the grass can also be a sign of some other problem such as a lawn disease, a fungus, too much shade, or even a faulty sprinkler system. Another sure sign is the small holes left in your lawn from grub foraging animals.
Grubs are most often found in sunny area lawns rather than shaded area lawns. And the most activity and greatest concentration of grubs is most often going to be found where the dead area of lawn meets with greener healthy lawn.
To see if the damage is really from grubs and to identify them, peel up the top layer of sod with with a flat shovel to inspect the area just under the roots. In many cases, the sod can just be lifted without a shovel due to the damage done.
Once you have the area exposed, you should be able to see the pests out in the open or with a little roughing of the soil. They are most often white, cream, or light brown C-shaped soft insects. And if you're seeing surface damage to your lawn, you should be able to see at least five per square foot.
Preventive Or Curative Treatment
While most lawns will have a grub or two or more, having a few rarely cause any signs of damage or warrant any alarm or need for treatment. However, if a test of questionable areas as explained above does reveal five or more grubs per square foot, curative treatment is necessary of the troubled spots.
Preventative treatment is more a means of treating the entire lawn with systemic insecticide in both Spring and late Summer. This almost always ensures that beetles won't be able to even lay viable eggs in the grass and those that do will die quickly.
Generally, the biggest deciding factor in preventive grub control is budget and expense. And of course, the larger the lawn, the bigger the expense. So most folks that have never had an issue usually opt for the curative approach.
Other deciding factors for preventive treatment are whether or not a lawn has had issues in the past, if a lot of mature beetles were present in the Spring, or if surrounding yards have issues. This may warrant a just in case approach.
Best Time To Treat For Grubs
Preventing grubs correctly is a matter of treating at the proper time. In most cases, within a few weeks after the beetles have emerged and are present, they will lay eggs in the soil. This is generally in July. Depending on soil temperature and moisture, the eggs hatch in about two weeks. At this point, the grubs will remain close to the surface and feed on grass roots. This is a good time to treat the lawn.
Early Spring can have some benefit. However, depending on the insecticide available to you, the effectiveness can dwindle by the time the eggs are deposited and marginal control can be expected. At this stage of the grubs life they are harder to kill since they are larger, not feeding anymore, and are deeper under the surface of the soil.
While I don't suggest not doing anything at all in the Spring, just keep in mind that any type of treatment will be marginal and generally not complete. We can slow them down a bit but the real results are going to come from treating at the end of the season and be obviously visible next year.
A simple step that can be done in Spring to slow down the visible damage is to apply a contact insecticide like liquid Sevin or malathion. A contact insecticide is necessary since they're not feeding. These insecticides can usually be purchased over the counter at your local home center, garden center, or feed store. Applied and watered in, these insecticides will kill some but generally not all of the grubs. As I said earlier, they are quite large at this stage, almost mature, and deeper under the surface.
So in order to get much better results, we treat lawns with a systemic long term insecticide in the late Summer and early Fall while the grubs are still small, feeding, and closer to the surface of the soil. The results are most always complete and satisfactory with one treatment.
Can A Grub Infestation Be Prevented?
It's difficult to predict if an individual lawn will get a grub infestation or not. Actually most don't. So to suggest that a yearly preventative treatment is a necessary expense may not be completely accurate or as necessary as say pre emergent weed control. Still, it would be logical to say that yes, an insect infestation in your lawn could be prevented with a yearly preventative treatment of long term residual insecticide.
For consideration, there are some factors that may indicate whether or not your yard is a candidate for an early preventative treatment.
For example, if your yard is the only green moist lawn in a sunny location surrounded by others that are not so, your yard would be the best candidate for an egg laying beetle to use. Or if you notice a lot of the Japanese beetles on your lawn in the Summer months, it may also be a worthy indicator. Still, it's not always certain. It really matters if it's in your budget and practical for you to do so.
Professional Grub And Insect Control
If you live in Carlsbad, Artesia, or elsewhere in Southeast New Mexico and would like a free inspection, evaluation, or advice, or if you would like a quote for a treatment, give Horizon Pest And Weed Control a call today at 574-725-9331.