Garden Mulch – Termites

Garden Mulch & Termites

Mulch cools the soil and helps slow water evaporation.

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The swarm of black ant-like insects fills the warm, sunny air next to the house, rising from the garden bed. They aren’t ants, and they have thick waists and long, narrow wings. Suspicious, you rake the mulch away from the moist soil around the foundation only to see big-headed white insects fleeing the sun as you disturb their nest — yes, that means you have termites.

Mulch, whether organic or inorganic, is used in the garden to maintain a consistent soil moisture level, reduce weed seed germination and to provide a decorative soil covering. Inorganic mulches include sand, gravel, lava rock, recycled rubber from tires and plastic sheeting. Organic mulches include compost, bark chunks, grass clippings, pine needles, shredded bark and wood chips. Mulch requires regular maintenance as some weed seeds germinate despite the mulch. Organic mulches are generally renewed each spring because they slowly decompose, becoming part of the garden soil.

There are three types of termites found in the United States. Dampwood termites such as the Pacific dampwood termite (Zootermopsis angusticollis) and Nevada dampwood termite (Zootermopsis nevadensis), require moist wood to thrive, including dead trees, stumps and houses with wood framing that touches the soil. Drywood termites, such as the western drywood termites (Incisitermes minor), are tolerant of dry climates, surviving even in the desert climate of the Southwest. The most destructive termites are the subterranean termites, which live in or near the soil and feed on any wood that touches or is near the soil. Among the species found along the West Coast are the western subterranean termite (Reticulitermes hesperus) and the desert subterranean termite (Heterotermes aureus).

Mulch and Termites

Mulch provides an ideal habitat for termites and other insects. The termites thrive in the moist soil under the mulch. If the mulch touches the siding or wood framing, the termites can migrate into the wood, destroying the interior structural supports of the house. Prevent termites from using mulch as a bridge into the house by raking the mulch back 6 inches from the foundation, and avoid watering in that area. A band of dry soil around the house helps prevent the termites from reaching the foundation. In addition, if grass or shrubs touch the house, the termites can use the plants to travel above any soil treatments for termites. Keep all vegetation trimmed between 6 to 12 inches from the siding.

Urban Myth

After Hurricane Katrina, rumors flew across the Internet, claiming that Formosan termites (Coptotermes formosanus) were being spread across the country in wood mulch made from New Orleans’ fallen trees. This urban myth was addressed in Iowa State University’s March 2006 newsletter, “Horticulture and Home Pest News,” by pointing out that any termites in the chipped trees were unlikely to survive the chipping process. In addition, if a gardener finds termites or other insects inside bags of wood mulch, there is a simple solution. By placing the bag of mulch inside a black garbage bag and setting it in the sun for several hours or days, the temperature of the mulch rises above 120 degrees Fahrenheit and kills hitchhiking insects — including termites.

Does landscape mulch lead to termites in your home?

The subterranean termites found in scattered, localized areas around Iowa are routinely found in wood chip mulch and other wood products on or in the soil (lumber scraps, boards, firewood, pallets, etc.). Does this mean, as some pest control advertisements claim, that mulch attracts termites to your home or that the mulch somehow causes termites? The answer to both questions is, “no.”

Landscape mulches contribute to a stable moist environment that is good for our trees and shrubs, and unfortunately, also good for termites and other insects. Termites in Iowa live underground in large, social colonies. Worker termites come to the soil surface (or higher) to feed on wood and other cellulose materials and carry it back to share with other colony members. Termites constantly explore for food by excavating a network of random, pencil-sized tunnels through the soil in the area surrounding their nest. Termites may tunnel for distances of up to 300 feet from their nest site. The presence of moisture favors termite exploration, tunneling and feeding. Therefore, any landscape mulch may improve conditions for termite colonies, whether the termites consume the mulch or not.

This does not mean you should avoid use of mulch, nor does it endorse one type of mulch as preferable over another. The same conclusion was recently reported from research at the Structural IPM Program at the University of Maryland. They studied the impact of landscape mulches on termite foraging activity in the laboratory and in the field. Termites that fed on a steady diet of either eucalyptus, hardwood or pine bark mulch suffered significantly lower survivorship than did termites fed the standard laboratory control diet of white birch. This result suggests that although we routinely discover termites in wood chip mulch, it is unlikely that they feed heavily on organic wood-based mulches.

In the field, termites were detected with equal frequency beneath mulches of eucalyptus, hardwood, pine bark and pea gravel and bare, uncovered soil. Sustained activity over time was significantly higher beneath gravel mulch. The hospitable conditions beneath mulch likely accounted for the termite foraging activity. However, there is no evidence that the moist conditions attract termite foragers from the surrounding landscape. Rather, when the termites wander into a suitable habitat they are more likely to remain and feed in that area.

Mulch recommendations

Keep mulch several inches away from the house foundation. Never allow mulch to cover windowsills or to contact house siding. Watch wood chip mulch for signs of activity if termites are present in your area. If you suspect termite activity contact several professional termite control services for inspections and estimates. Termite treatment is best left to professionals experienced in the various methods of termite control. Take your time. Do not be rushed or pressured into a hasty decision. Termites work slowly and your house will not be ruined overnight. Deal with reliable firms and get several inspections, opinions and estimates.

This article originally appeared in the May 4, 2001 issue, p. 48.

Does Mulch Draw Termites? Should I Keep It Away From My Foundation?

The Full Answer May Surprise You

Some readers, out of an abundance of caution regarding pest control, write in to ask if a layer of mulch applied next to a house foundation will draw termites (and therefore should be avoided). The short answer is this:

  • To be on the safe side, you can leave a 1-foot-wide swath of ground mulch-free all along your foundation (and keep the ground here as dry as you can).
  • Outside of this “mulch-free zone,” you may apply mulch (as people often do to suppress weeds in their foundation plantings), but limit its depth to just a few inches and inspect it vigilantly for termites.

Now that you have the short answer, let’s explore this issue in greater depth.

Drainage (Moisture), Termite Control, and Your House Foundation

When it comes to termite control, opinions vary on the degree of caution one must exercise when applying mulch near a house. But when mulching foundation plantings, you should, at the very least, be aware of termite issues, especially if:

  • Termites are known to be a concern in your area.
  • You, yourself have had trouble with termite pests in the past.

The very word, “termites” is enough to make one shudder, and with good reason. That is why it may be best to play it safe and err on the side of caution when mulching near your home’s foundation.

Drainage and termite control are two matters to keep on the front burner when applying mulch to a foundation planting. Ensuring adequate drainage is relatively simple: Grade the ground underneath so that it has about a 5-percent slope away from the house, to channel water away from the foundation. But termite-control recommendations are more complex.

Can I Mulch Around My House, or Will This Draw Termites?

Consider the various sub-questions implied when we ask such a question:

  1. Should the mulch be allowed to come into contact with the foundation?
  2. If so,
    • How deep a layer of mulch is acceptable?
    • And how close should the mulch be allowed to come to a wooden surface?
  3. Are some types of mulch preferable when it comes to termite control? Does a wood mulch actually draw these pests to a yard, in search of a snack?

Each of these termite-control questions deserves individual treatment.

There is some disagreement over the answer to the first question above. Some advise against letting the mulch come into contact with the foundation at all (you certainly should not allow such contact if a termiticide was applied to the soil along the foundation when your house was built). In other cases, if you want to err on the side of caution for termite control (and it is hard to fault a homeowner whose general policy is, “Better safe than sorry”), then this would be the correct answer for you. As mentioned above, simply keep your bed of mulch a foot or more away from the house (if this mulch-free zone allows you to sleep better at night, then it is a precious foot of space, indeed).

If you are going to be a bit less paranoid and will let the mulch come into contact with the foundation, then limit the depth of the layer of mulch to about two inches (in fact, even if kept further away from the house, a mulch layer in a foundation bed should not be much deeper than this, with four inches being maximum depth). But how close should the mulch be allowed to come to a wooden surface? Burnett’s Landscaping in Salem, Connecticut (U.S.) recommends “at least eight inches of exposed foundation between the top of the planting bed and the wood sill plate of the house structure.”

Finally, when it comes to the best type of mulch to use when termite control is a concern, there is a widespread misconception. Folks assume that, because termites eat wood, only wood mulches present a problem. That is a myth. There is also the separate question of whether, technically speaking, mulch actually draws termites to your land.

The issue is not termites being drawn to a property by the promise of a wood mulch that they can eat, but rather termites that are already present (in the soil) exploiting the mulch as a hiding place, using it as a launching pad to invade your house. Termites like moisture, and all mulches provide that to some degree. In fact, good moisture-retention is one of the prerequisites for the most effective mulches. Your plants enjoy this quality in a mulch, but so do the termites. And remember, even mulches that retain less moisture (such as stone mulches) still furnish pests with a place to hide. To sum up, the case is not so much that mulch draws termites to a property (they were probably there already), as it is that mulch makes life more comfortable for these pests. And placing mulch near the foundation, specifically, just invites them to rise up out of the soil and search for ways to penetrate your house’s walls. And who needs that, right?

The good news is that there are actually some kinds of wood mulch that termites dislike:

  • Cedar mulch
  • Mulch that comes from the heartwood of cypress

Incidentally, it is more accurate to say that termites eat cellulose than to say that they eat wood. Cellulose can be found in the cell walls of plants (not just trees). Consequently, termites give you another reason not to like them: They can damage your landscape plants.

Home Termite Control Requires Diligence

So what is a homeowner worried about termite control to do? First of all, if you do not already know, find out what the heck a termite looks like, anyway, using the termite picture above for identification. Next, be diligent and inspect the mulch in foundation plantings regularly, to determine if any termites are present. If you find any, do not procrastinate: Contact a reputable professional in the termite-control business immediately.

4 Things You Need to Know about Termites and Mulch

The Right Mulch can help prevent Termite Infestation!

Termites and Mulch can go together to prevent Termite Infestation!

Termites can cause a lot of damage to your clientโ€™s property, so thereโ€™s a legitimate reason to be concerned about the ways they can infest a home. Because termites love wood, and mulch is made of wood, it may feel like common sense for your customers to make a strong association between both things.

Unfortunately, there is a lot of confusion out there about the relationship between termites and mulch. If you or your clients have unanswered questions about this relationship, we might have the answer for you. With the right information, you can improve your chances of preventing a termite problem at any property you service.

1. Termites Are Unlikely to Come with Packaged Mulch

Itโ€™s been a popular rumor for some time that termites travel around in bags of mulch just waiting to infest the building they end up calling home. The truth is, however, that termites rarely survive long enough in bags of mulch to make it to any landscape. There are multiple obstacles to their survival.

  1. Surviving the chipping process is highly unlikely.
  2. Once separated from their colony, termites tend to die very quickly.

Termites are also known to have much shorter lifespans if they feed on the wood contained in mulch than on solid wood. The chance of you opening a bag of mulch with a live termite while working on a clientโ€™s property is slim to none.

2. Termites Are Attracted to Mulch, But Not for the Reasons You May Think

Itโ€™s reasonable to think that termites would be attracted to mulch because many mulches are made, at least partly, of wood. Termites donโ€™t love mulch because they want to it eat the wood, however. They love it because it provides a cool and moist space. Thatโ€™s why you should worry less about mulch containing termites from the store and more about mulch attracting the termites that may already be living near your property.

Piles of mulch around your house can create a very inviting environment for termites and other insects and critters in the area. Itโ€™s more important to pay attention to environments around your home that may be friendly to termite growth rather than introducing a problem with a bag of mulch.

3. Termite Resistant Mulches Are Available

How attracted termites are to a particular mulch depends on the ingredients used to make it. If youโ€™re really concerned about termites infesting your clientโ€™s property, mulch colorant manufacturers can make sure to include ingredients that are toxic or a deterrent to termites is crucial.

For example, Cypress sapwood, slash pine, and loblolly pine is delicious to termites while Cypress heartwood, melaleuca, California redwood, and eucalyptus are known to shorten their lifespan.

According to studies from the University of Hawaii, cedar can repel, kill, or inhibit termite colonies from developing. Most mulches donโ€™t come treated with any anti-termite chemicals, but the ones that do should be clearly labeled.

4. Termites and Mulch โ€“ You Can Still Use Mulch and Prevent Termites

Overall, mulch is a problem when it comes to termites because it offers them a place to travel and call home, not because bagged mulch is a meal or a source for termites where none previously existed.

In fact, other ground coverings, like gravel, offer just as friendly an environment for termites to approach home siding. Despite these issues, you can still protect your clientโ€™s home by treating the perimeter with subterranean termite control chemicals before you place mulch over it.

Termites and Mulch โ€” According to The Institute of Food and Agricultural Sciences at the University of Florida, landscapers should be careful not to lay mulch thicker than 4 to 6 inches next to siding. Thick mulch can create termite pathways and prevent proper pest inspections. You can also use bait stations as well as insect growth regulators or boric acid solutions to control termite populations as needed.

Youโ€™re pretty much guaranteed to find termites in the soil of any property, so let your clients know that creating a bare and boring lawn because theyโ€™re worried about the connection between mulch and termites is pointless. Termites usually have plenty of wood to eat in the soil and will never bother looking for food in their home. Homeowners can add beautiful colored mulch to their homes with peace of mind by knowing exactly where the real risks are.

โ€œTermites and Mulchโ€œ, by Brian Mase

Wood Mulch And Termites โ€“ How To Treat Termites In Mulch

Itโ€™s a well-known fact that termites feast on wood and other substances with cellulose. If termites get into your house and are left unabated, they can wreck the structural parts of a home. Nobody wants that. Many people are concerned about termites in mulch piles. Does mulch cause termites? If so, we wonder how to treat termites in mulch.

Does Mulch Cause Termites?

You may, on occasion, see termites in mulch piles. But mulch does not cause termites. And termites donโ€™t typically thrive in mulch piles. Termites typically pre-exist deep underground in moist environments. They tunnel through the earth to find woody food products for their food.

Mulch typically dries out enough that it is not a conducive environment for termites to build a nest. Termites in mulch piles are possible only if the pile is constantly kept very moist. A more realistic termite risk is caused by piling mulch too high up against your siding so that it provides a bridge over the termiticide treated foundation and into the house.

Large pieces of wood, boards or pressure treated railroad ties are even more conducive to hosting a termite nest than mulch piles.

How to Treat Termites in Mulch

Do not spray insecticides into your mulch. Mulch and its decomposition process are very important to the health of the soil, trees and other plants. Insecticides kill all the beneficial organisms in your soil and mulch. That is not a good thing.

It is best to maintain a low mulch buffer area from 6โ€-12โ€ wide around the perimeter of your house. This will stop termite bridges. Some experts recommend no mulch at all in this buffer area while others say a 2โ€ max mulch layer around your house is fine.

Keep this area dry. Donโ€™t water directly in the perimeter zone of your house. Remove large wood logs, boards and railroad ties that are stored against your house for future DIY projects. Keep an eye out for termites as a matter of course. If you start to see termites regularly, call in a pest control expert to inspect the situation.

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