A large number of grubs can cause a significant damage to a grass lawn, vegetable or flower garden. Grubs primarily feed on grass roots and other organic matter found in the soil. So, where do grubs come from?
Grubs are typically larvae of scarab beetles. During late summer and in fall, the beetles lay eggs and burrow them into the turf. The eggs hatch into larvae that start feeding on roots and other organic matter in the soil.
What do grubs come from?
In late June, or early summer, grubs mature into beetles as they leave the soil and start feeding on foliage. The new beetles also lays eggs and the cycle continues. If not treated, grubs population increases posing a great threat to your lawn or garden.
During mid to late summer and in early fall, grubs are more active and close to the top soil. This is when to treat for grubs in lawn. During winter grubs are deep into the soil and in spring they are changing a stage thus any treatment or control measure will be ineffective.
Grub damage in lawn – Signs
A small number of grubs, less than 5 per square foot of soil does not pose a serious threat to your grass. But when their population increases to more than 10 grubs per square foot, a significant damage will be noticed in your lawn or garden.
Grass will start turning brown in patches and eventually dry out and die. You will notice random brown grass in your lawn, a spongy feeling when you walk on and they become easy to pull up. Grubs also make grass to become highly vulnerable to drought, diseases and other stressors.
A large population of grubs in a lawn will attract predators such as birds, moles, skunks and raccoons that will dig holes in your yard to grab the grubs. Since these animals also search for other insects and worms in the ground, their activities alone cannot point to presence of grubs. You should therefore inspect soil for grubs.
How to identify grubs in the soil
Grass can turn yellow, brown or die for many reasons. To be sure of what you are dealing with inspect the soil to warrant a control measure. Here is how to check a lawn for grubs:
- Survey an area of your turf showing signs of grubs such as yellow patches
- Use a spade to cut a section of turf, about a square foot 4 inches deep in several areas
- Pull back the section and inspect the turf, thatch or soil for grubs
- If you find at least 10 grubs per section, take a control measure, if less than 5 do not bother
- Replace back the sample sections and water to prevent the sod from drying
How to Get Rid of Lawn Grubs
Biological and chemical methods of getting rid of lawn grubs are available. While choosing on a method, timing is very important. Let us begin by looking at natural ways of controlling grubs.
1. Beneficial Nematodes
Application of Beneficial nematodes for grubs can completely eliminate grubs and other destructive pests in a lawn or garden. Nematodes are a group of tiny parasitic worms that are capable of invading and killing lawn pests including grubs.
Although not an instant remedy, introduction of nematodes is a safe eco-Friendly and effective way of controlling grub worms in the soil.
Order your nematodes from a reputable retailer and promptly apply as directed. Since they are microscopic living organisms, using them immediately after purchase will make them effective. Bad storage and delay may make them sterile and ineffective.
Nematodes are usually mixed with water and applied on the grass using a watering can or a sprayer. Note that, this method can take up to three years to start working. This is after the nematodes have multiplied and established a large colony suitable to tackling grubs.
2. Milky Spore Treatment
This is a bacterium substance that causes a disease that attacks and kill white grubs of Japanese beetles. Like Nematodes, application of milky spores is a natural, safe and eco-friendly method of controlling white grubs.
Although beetles come in many species, you may want to try this method in conjunction with nematodes as an effective fix. After ordering your milky spores, apply as directed and allow enough time usually more than a year for the Japanese white grubs to disappear.
Grubs and beetle eggs thrive in moist conditions. Limiting irrigation of your lawn for a few weeks during summer can render them dehydrated and dead. While this is likely to affect your grass as well, it should spring back to normal when you resume watering.
While a good layer of thatch is beneficial to a lawn, too much can bring pests and aeration problems. You can discourage beetles from laying eggs in your lawn by dethatching. This is the removal of a layer organic matter formed in your turf. Before application of nematodes or milky spores, dethatching will help in ensuring that the ingredients are effectively absorbed into the soil.
5. Natural pest repellents
Neem oil is an example of a natural pests repellent which is also effective in controlling beetles and grubs. Spray need oil on your lawn overnight when grubs and beetles are active. Besides, be careful with homemade grub killers containing borax. In excess, the element will also kill grass and other plants.
6. Chemical control
Using a pesticide to kill grubs and beetles is instant but you will end up also killing other beneficial insects and microorganisms in your garden or lawn. Microbial activities in the soil helps in enriching soil with nutrients. It is thus important to protect them. Additionally, chemical controls are toxic to use around family and pets.
Chemical grub treatments come in either curative or preventive formulas. The outcome will depend on when you apply your grub control pesticides. Curatives formulas should be applied in late summer or during fall and in spring when grubs are actively feeding.
If you suspect grubs in your neighborhood or spotted some signs of grubs in your lawn, apply a preventive formula in spring when soil warms or in early summer.
When using a chemical treatment, put on a protective gear to avoid inhaling or contact with eyes and skin. Use away from pets and children. Consider spraying on a calm sunny day during summer.
Will grub damaged lawn grow back?
After controlling grubs, a damaged lawn is likely to grow without doing anything, although at a slower pace. To restore the green glory of your grub damaged lawn faster, you need to do some repairs ideally in the fall or early spring.
Rake to remove the dead grass and aerate your lawn. Find matching grass seeds and broadcast on the affected spots. Cover them seeds with a thin layer of either straw or soil to protect the seeds from sun or pests.
Sprinkle the entire lawn for approximately two weeks without flooding for the seeds to germinate and grow. Make the grass thick and lush by applying a fertilizer as you resume normal watering.
Pests are a great threat to lawns, flower bed and vegetable gardens. Inspecting and controlling grubs before they form a large colony is very important. If left untreated, grubs can wipe out the entire lawn making your whole outdoor investment to go down the drain.
- Home & Garden Information Center: White Grub Management in Turfgrass
- University of New Hampshire: How do I Treat for Grubs in my lawn?
- Michigan State University: How to choose and when to apply grub control products for your lawn