Mulch is one of the best tools in the home gardener’s arsenal. Used properly, mulch can inhibit weed growth, regulate soil temperature (protecting vulnerable roots from frost or extreme heat), retain moisture to reduce the need for watering, and, in the case of organic mulch, provide your plants with much-needed nutrients.
While there are many advantages to using mulch on your flower beds and vegetable gardens, with these benefits come a few drawbacks. One of the biggest issues for gardeners using mulch is an increase in the presence of bugs and insects. You may be wondering if these insects are beneficial or harmful, and if anything can be done to reduce the number of bugs living in your mulch.
Read on for a better understanding of the mulch options available to you, the types of insects you may encounter, and what you can do to get rid of them.
Does Organic Mulch Attract Insects?
There are two categories of mulch: organic and inorganic.
Organic mulch is made from materials that were once alive, such as bark or wood chips, pine needles, straw, compost, leaves, grass clippings, and cocoa hulls. The advantage of using organic mulch is that it will provide nutrients to your soil as it breaks down. It can also be handily turned into your soil at the end of the season.
Some types of organic mulch, such as compost, will noticeably increase the presence of insects immediately, as it presents a ready-made food source. Other types of organic mulch will also appeal to many bugs, simply as a shelter to burrow beneath.
Cedar chips would be the exception to this rule, especially when they’re fresh. Cedar exudes an oil which most insects find unappealing.
What About Inorganic Mulch?
Inorganic mulch is manmade. Popular forms of inorganic mulch include rubber chips (made from old tires), crushed seashells, gravel or pebbles, landscape fabric, or black plastic sheeting.
Although bugs do not find any food source within this type of mulch, it offers shelter in the same manner. After it’s been in use for even a short time, you will likely find insects living in or beneath your inorganic mulch, though perhaps not as many in comparison to organic mulch.
What Type of Insects Can You Find in Organic Mulch?
So, what’s crawling around in your mulch? Whether it be a vegetable garden or flower beds, the many insects you may find lurking beneath your mulch include:
- centipedes and millipedes
- spiders
- roaches
- termites
- ants
- silverfish
- earwigs
Do Bugs in Your Mulch Pose Any Risks?
While most of the insects attracted to your mulch are considered harmless, one notable exception is termites. For this reason, many homeowners choose not to use wood-based mulch in flower beds close to the home’s foundation (excepting cedar). As a general rule of thumb, all mulch should be kept at least six inches away from all structures.
Another problem insect would be certain types of ants, specifically fire ants and carpenter ants. Both of these ants can damage the roots of your plants, and attract other garden pests, such as aphids.
The majority of insects in your mulch, while undesirable to encounter when gardening, are generally harmless.
Are There Any Benefits to Having Bugs in Your Mulch?
Bugs have an important role to play in your garden’s ecosystem. The insects living in organic mulch will help break down the material, releasing nitrogen into the soil, which, in turn, feeds your plants.
Furthermore, many bugs taking shelter in the mulch, such as spiders, centipedes and millipedes, feed on garden pests such as aphids, beetles, flies, baby snails, and slugs.
How To Get Rid of Bugs in Your Mulch Garden?
There are several approaches to ridding your mulch of insects, depending on whether you’re comfortable using insecticides, or are firmly committed to organic gardening.
Spray with Chemical/Natural Insecticide
The quickest way to get rid of insects is to spray the mulch with insecticide. This may involve several applications over a week or two, in between which you may want to flip or stir the mulch to completely expose all surfaces.
Alternatively, you can remove the mulch with a shovel, and spread it thinly on a tarp. Spray the mulch with insecticide, and return the mulch to the garden, making sure you leave a minimum of one inch perimeter between the stalks of the plants and the mulch.
Using the same method, organic gardeners can swap out chemical pesticides for a neem oil application. Neem oil is made from the nuts of the neem tree, and contains a compound called Azadirachtin, which is a natural pesticide. Neem oil can also be used as a topical spray on the leaves of your plants, but when using it as a soil drench, it will help eradicate many undesirable bugs living in and beneath your mulch.
Combine 1 tsp. of neem oil with 4 cups of water and add a drop of liquid dish soap. Neem oil is reported to be safe for beneficial insects and creatures, such as bees and earthworms.
Neem oil can burn certain plants, so be careful as to what you apply it to and when you apply it. Apply later at night, if applying in direct sunlight you are likely to cause the plant to burn.
Spraying your mulch with either a chemical or natural insecticide is a speedy method for initial results, but you may find persistent bugs, such as termites, will return. If this happens, you may want to replace your mulch with another type. Switch out your wood chips for pine needles in the instance of termites. Switch your compost mulch for straw if you’re seeing roaches. If you’re intent on using wood mulch for the aesthetic appeal, try using cedar mulch.
Try Using Inorganic Mulch
If your mulch is being used on flower beds as opposed to a vegetable garden, consider using an inorganic mulch, such as rubber or pebbles, which will not be as tempting to insects who rely on mulch as a food source. Never use rubber or plastic mulch in your vegetable garden, as chemicals may leach into your soil over time.
Grow Flowers that Naturally Repel Insects
An alternative organic gardening trick is to plant flowers known for their naturally repellent properties. Chrysanthemums, geraniums, lavender, and marigolds all emit scents that many insects will avoid. Planting these in your flower beds and between rows of vegetables is a colorful and safe way to diminish pests, both within the mulch and on the plants, themselves.
Attract Birds to Your Garden
Attracting birds to your gardens will also go a long way in keeping down the insect population. Provided you’re not using row covers, many birds will scratch and peck through mulch in search of tasty bugs to dine upon. Placing birdhouses, birdfeeders, and birdbaths on your property is a pleasant and rewarding way of battling garden pests.
How Do You Get Rid of Bugs in a New Bag of Mulch?
Worried that your store-bought bag of mulch may be bringing bugs into your garden? Try this neat trick:
Transfer the mulch to black garbage bags and secure the ends. Leave them in a sunny area on a hot day for several hours. Once the interior of the bags has reaches 120 degrees F, the high heat will effectively kill any insects lurking in the mulch!
Tips to Prevent Insect Infestations in Your Mulch:
There are many things you can do to prevent insect infestations in your mulched gardens before they get out of hand. Try to incorporate these practices:
- Don’t spread mulch too thick. The optimum depth of mulch is no more than three inches.
- Don’t let mulch stay wet. Allow mulch to dry before watering again. After several days of rain, consider stirring or spreading the mulch with a rake to help it dry out.
- Remove ant hills from mulch as soon as they’re visible. If you transport anthills to the same area to dump them, pile them onto each other. Ants are territorial, and the opposing nests will fight to the death.
- If you’re losing the battle of the bugs, remove the mulch, and either treat it with chemical or natural pesticides, or replace it entirely.
- Don’t use kitchen compost as mulch without letting it age. Fresh kitchen compost will attract roaches and ants.
- Attract birds to your gardens by tempting them with food, water, and shelter.
- Plant flowers that are known for their natural insect-repellent properties between shrubs and vegetables
Mulching is an ideal way to counteract many naturally occurring unfavorable conditions, such as climate extremes and weed growth. Experiment with different types of mulch to find the ideal match for your gardens, while keeping the bugs at bay.
Michelle Weaver is a former pastry chef of thirty years who reinvented herself during the pandemic, now happily earning a living through freelance writing and selling her art. She and her significant other live in an 1895 farmhouse in North Carolina, where they have several acres, allowing her to garden to her heart’s content. When she’s not playing in the dirt, she enjoys hiking in the nearby mountains, creating new vegetarian recipes, and photographing the wildlife that comes to visit.