This grub control guide for Cedar Rapids covers everything from how to identify grubs and spot signs of lawn damage, like wilting, to prevention and control using trichlorfon or chemical-free methods like beneficial nematodes.
Controlling white grub populations and the lawn damage they create can vary greatly from year to year, from one location to another, and even within the same lawn. This is due to many factors, including, but not limited to, differences in beetle numbers, weather, turfgrass health, soil conditions, and others. Let’s dig in.
Which Grubs are Common in Cedar Rapids?
The Japanese beetle, June beetle, and northern masked chafer are the most frequently encountered grubs in Cedar Rapids. The bluegrass billbug is also a common nuisance, but their activity occurs at a different time.
The larvae inflict the most damage, although some adults can also be destructive. These pests feed on grass roots and other soil matter, killing sections of the lawn’s grass. As they mature, the white grubs become adult beetles and emerge from the soil to seek a mate and lay eggs.
Japanese Beetles (Popillia japonica)
- These larvae devour turfgrass roots, causing the grass to turn yellow and appear wilted and sparse.
- Additionally, the turf damage from this grub makes the grass easy to pull up from the soil, like a loose carpet.
- This eventually leads to browning and the death of the turf.
- As an invasive species, adult Japanese beetles consume the leaves, flowers, or fruit of more than 300 plant species.
June Beetle (Phyllophaga spp.)
- June beetles, also known as May bugs/June bugs, are commonly found across the United States.
- Both larvae and adults can damage turfgrass.
- While the adult beetles consume leaves and are usually viewed as a minor nuisance, the larvae can cause significant damage.
- The larvae eat the roots of your grass. Eventually, the grass will show signs of stress, like wilting and appearing parched, which could result in losing an entire turf area.
- Animals that feed on the grubs can exacerbate the issue by digging up the turf in their search for the grubs.
Northern Masked Chafers (Cyclocephala borealis)
- The northern masked chafer inhabits the country’s northern regions and loves eating all the cool-season grasses.
- Dwelling in the soil, it eats the roots of your grass while still in its larval stage, leading to the turfgrass wilting, weakening, and thinning.
Note: For more specific information on Japanese beetles, check out our article, How to Get Rid of Japanese Beetles.
Life Cycle of Grubs
Understanding the grub life cycle will give you the information to help you decide on the best method to combat these pests. Check out the progression of their life cycle below:
- It takes one year for them to complete their life cycle from egg to larva, pupa, and adult.
- These beetles begin flying in late June.
- They deposit eggs in the turf during July.
- The eggs hatch within 2 to 3 weeks, giving rise to the small white grub.
- The new generation of root-munching pests begins feeding immediately after hatching, with peak feeding occurring in early fall.
- These larvae grow quickly and reach a length of 1 inch by late August or September.
- During the winter and spring, white grubs burrow several inches deep into the soil to hibernate. In the spring, they move closer to the surface but cause minimal damage as they await pupation in June. After emerging as adults, they restart the cycle.
Signs of Grubs in Your Lawn
The presence of grubs in your lawn can manifest in several ways. You might be surprised at some indicators that grubs are enjoying the roots of your grass. These signs can help you identify “the root of the problem” (excuse the pun), including:
- Thinning, yellowing, and dying grass with damaged roots
- Random patches of brown grass appear irregularly across your lawn
- Your grass feels excessively spongy and pulls up easily.
- Increased vulnerability of grass to drought and other stress factors
- You see moles, squirrels, skunks, crows, and raccoons digging in your lawn.
In addition to finding signs of grub activity on your lawn, there are other ways to help determine the presence of grubs around your home:
- Walk around your lawn after sunset, and look for flying beetles above the grass. Focus on well-lit areas.
- Watch for beetles hitting your window screens (if you enjoy having your lights on and windows open). If so, follow up by inspecting the rest of your lawn for beetles hovering over the grass.
- Leave a coffee can or mixing bowl filled with water outside and your outdoor light on during the evening and overnight hours. In the morning, check the container for floating beetles. (Kiddie pools can also be effective for this purpose.)
- Observe your neighborhood. If your neighbors have previously experienced grub issues, there’s a good chance they might still be present in the vicinity.
Note: For more detailed information on how and when to kill lawn grubs, check out our article, Lawn Grubs: How and When to Kill Them.
How to Inspect Your Lawn for Grubs
If you’re concerned about grubs in your soil, it’s a good idea physically to check to see if there are enough to justify action. It’s normal for a few grubs to be in the soil, and your grass should be able to handle a small number of grubs feeding on the roots.
However, if there are more than just a few, that may be a reason to do something about it. Here are six steps for checking your soil for grubs:
1. Look at the areas of your lawn that seem suspicious. August and September are good times to check because the grubs will be active and close to the soil’s surface.
2. Use a spade to cut out square-foot sections of turf, about 2-4 inches deep, in several different areas.
3. Pull back the square foot section to expose the soil underneath.
4. Examine the turf, thatch, and soil to see any grubs.
5. Notice if there are fewer than five grubs per sample. This is considered normal and doesn’t require action. However, if you find more than five grubs per soil sample, it’s time to consider action.
6. Replace the squares of sod and gently pat them down. Water the patches to prevent them from drying out.
3 Ways to Deal With Grubs
Iowa State University suggests three main ways for homeowners to deal with grub problems. Homeowners’ approaches can differ, depending on how much lawn damage they can tolerate, how comfortable they feel using insecticides and pesticides, and their budget.
Using insecticides to treat white grubs can be expensive and difficult to justify from an eco-friendly standpoint. Consider the three approaches: prevention, wait and watch, and do nothing.
Prevention
This first approach is primarily used on commercial turf, such as golf courses, rather than residential lawns. It involves applying preventive insecticide to turf once a year, between early June and August 15, even if you don’t see any pests.
An alternative is to treat only the areas that have been previously damaged, as beetles tend to return to the same areas in successive years.
Wait and Watch
The wait and watch approach involves applying a curative treatment only when and where it is needed, as determined by the homeowner. Cedar Rapids homeowners should keep an eye on their lawns for early signs of grub damage. Grass wilting and turning brown during August to early September are typically signs of grubs eating.
The risk when using this method is that you might still lose some grass, especially if your irrigation system or heavy summer rains accelerate grass growth during July and August.
Furthermore, signs of severe damage may not show up until it’s too late to put down an effective treatment (from late September to late October).
Do Nothing
The last option is to do nothing, meaning take no action. It involves adopting a mindset of, “It is what it is; after all, it’s just grass.” This approach may be effective if you can determine how many years it has been since you last experienced grub damage.
Think of it this way: It might help if you do the math to justify the do nothing approach. Divide the cost of replacing the grass by that number of years. If the average yearly cost is less than the price of insecticide, then choose to do nothing and deal with occasional damage when it happens.
How to Get Rid of Grubs
Grubs getting you down? No worries. Grub control can be done using chemicals, or if you want a more eco-friendly approach, there are non-chemical methods available as well. It’s totally up to you.
Curative Treatments (Chemical)
- Trichlorfon is an effective chemical for grub control.
- Carbaryl also works to cure your grub infestation.
- Apply when the grubs hatch in mid-August.
Note: After applying trichlorfon or carbaryl, it’s important immediately to water the area with half an inch of water (either by hand watering or with an irrigation system). This is crucial for achieving effective results and aiding in the recovery of damaged turf.
Curative Methods (Chemical-Free)
A few alternative methods are available for treating grubs:
- Ground beetles and ants are beneficial insects that feed on eggs and young grubs, while parasitic wasps and flies target older grubs. Avoid applying insecticides to your lawn to encourage these species.
- Naturally occurring pathogens such as fungi, bacteria like Bacillus thuringiensis galleriae (Btg), and protozoa can kill or weaken grubs. These pathogens already exist in the soil, but the chemicals you apply may kill them. Therefore, consider holding off on any other chemical grub treatment and letting the pathogens do their work.
- Milky spore disease can help combat Japanese beetle grubs. However, it’s worth noting that it is a relatively weak pathogen whose success rate is highly variable at best.
- Beneficial nematodes are microscopic roundworms that can be used to combat grubs in your lawn. Beneficial nematodes pose no harm to humans, pets, or beneficial insects, making them a safe and non-toxic option for pest management in outdoor spaces.
How to Prevent Grubs
Homeowners who haven’t seen any signs of grubs can be proactive and prevent them from invading the lawn. Here are some chemical and eco-friendly (non-chemical) methods to keep these these root-chomping pests at bay:
Prevention (Chemical)
- Common preventive treatments include chlorantraniliprole (Grub-Ex) and imidacloprid (Merit).
- Apply preventive treatments between June and August 15.
- These products have a lasting impact and target grubs as they consume the chemicals during feeding in August.
- After applying the insecticide, it must be watered into the soil with at least 1/2 inch of water from rain or irrigation.
Prevention (Chemical-Free)
Prevention is the greatest weapon in your grub-fighting arsenal. These four non-chemical approaches combined will keep those “grubbing” pests from invading and devouring your grass roots.
Dethatch and fertilize
- Dethatch when your thatch becomes 1/2 inch or greater. September is the best time to dethatch, especially lawns with Kentucky bluegrass.
- Fertilize with nitrogen once yearly, usually in late October or early November.
Aerate
- Aerate your lawn. Kentucky bluegrass and other cool-season lawns in Iowa benefit from aerating in September and April.
- Aerating prevents the grubs’ food source (thatch) while also encouraging root growth.
Mindful mowing
- To control grubs in your lawn effectively, set your mower to its highest level, which can be between 3.5 to 4 inches, to encourage deeper and stronger root growth.
Grub-tolerant turfgrass
Selecting the appropriate grub-tolerant turfgrass is crucial. For instance, tall fescue generally requires about eight to 15 grubs per square foot before showing any damage. In contrast, Kentucky bluegrass and perennial ryegrass can sustain damage with just six to 10 grubs per square foot.
Neem oil
Neem oil (a botanical pesticide) can also prevent grubs by repelling them. You can make a DIY solution by mixing neem oil with water and spraying it using a hose-end sprayer or pump sprayer.
This oil comes from the neem tree and will also inhibit grub feeding, egg laying, and their growth. Late summer or early fall is the best time to apply.
FAQ
Can I Use Integrated Pest Management (IPM) for Grubs?
No and yes. Using some principles of Integrated Pest Management (IPM) to combat grubs in turfgrass is highly challenging. For example, monitoring, a key tenet of IPM, is impractical, as inspecting the grub population requires labor-intensive and potentially damaging turf inspection methods. Research indicates that the necessary number of samples is unfeasible.
However, IPM also involves eliminating factors pests require to survive, such as reducing their food and shelter, which is very doable for homeowners. For minor infestations in a home lawn, aerate or dethatch yearly and strengthen the grass with proper fertilization and mowing.
Overseeding can also repair any damage done by grubs. All of these are simple, chemical-free IPM methods that can prevent or manage minor grub activity.
Note: IPM relies on pesticide sprays and granular barriers only as a last resort.
Should You Dethatch and Aerate Before Treating for Grubs?
It depends. If your lawn has a thatch layer thicker than 1/2 inch and you’re planning to treat for grubs, it might be a good idea to dethatch and/or core aerate first.
To learn more, check out our article, Lawn Aeration in Iowa: Everything You Need to Know.
Can You Overseed and Apply a Grub Control Treatment at the Same Time?
Yes, you can overseed your lawn and apply grub control treatments (grub killers and grub preventers) simultaneously without any negative impact on the grass seed. Thankfully, the additional task of killing grubs won’t interrupt your lawn care schedule for Iowa.
Note: If you aren’t sure which cool-season grass seeds work well for your Cedar Rapids lawn, check out our article, Best Grass Seed for Iowa Lawns.
Call in the Pros
Adding grub control to your lawn care routine of mowing, fertilizing, weed control, and seeding can feel overwhelming for the average homeowner in Cedar Rapids. So, don’t get stressed out over it all. LawnStarter connects you with the best local pros in your area.
Main Image Credit: Greg Schechter / Flickr / CC BY 2.0
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