Will mulching around my plants encourage termites?

This question was raised from a friend (we will call her Juanita, because that is her name and it’s rude to call people other names), so here’s the research I could find to answer your question, I hope you enjoy and feel comfortable with your decision.

This topic is fiercely debated on the internet, but few seem to back up their conclusions with any educational research. I am going to try to collect the facts from experts in the field.

Let’s Start with some Perspective

I thought it would be easy to find the estimate for costs associated with termite damage to homes, however the information that the termite industry puts out does not make sense. They claim $5 Billion dollars are spent every year on control ($1.3 Billion) and repair ($3.7 Billion) costs, with the average repair about $3000 and 600,000 homes affected. If you multiple the number of homes by  the cost you get $1.8 Billion in total damages not $3.7 Billion. It looks like someone might be over-inflating the numbers to drive up business, or residents are underestimating their repair costs or forgot during the survey that they had termite repairs done that year – not likely. I like to look at insurance to tell me how likely the issue is and how costly to fix. Some people have been able to find termite insurance through a pest control company for $300 – $400 per year depending on where you live, which includes an annual inspection (obviously the company selling the insurance knows that if they catch the infestation early and treat it, there will not be any substantial repair costs). Most bait and control plans cost more than the insurance in these areas and may or may not include insurance against infestations and their associated costs…so that tells me that the bait and control plans are overpriced. I might as well just buy the insurance, since the bait and control plans may not be 100% effective.

There are several ways to figure the total damage but $1.8 Billion on repair of homes in the US from termite damage and about $1.3 Billion on controls and baits seems to align the data, which also matches some of the educational literature that estimate about $3 Billion in total control and repair costs in the US. Chances are still fairly low that you will have extensive damage from termites, less than 1% chance per year. Paying $1000 to $3000 per year or more for termite control does not seem to not make good financial sense, better to put that money in a bank account for the off chance that you have a termite problem, and take steps to minimize your potential hazards. If you find termites in or around your house this would change my suggestion.

Termites

With that out of the way, let’s get into the background of termites. There are three main categories of termites in the United States: subterranean and wood termites (dry and damp). Termites consume mostly on dead plants and trees containing cellulose, which is helpful in nature to decompose knocked down trees, etc. which would otherwise take much longer to break down. Since drywood and dampwood termites do not need soil in which to live, they are unaffected by mulch so I will focus this blog on Subterranean termites. Subterranean termites establish themselves in the soil for one reason, moisture. If enough moisture is consistently available inside a house, say from a dripping pipe, termites can establish an alternative colony inside the home. It’s estimated that 20% of homes will have a subterranean termite infestation at some point if the homes are located in areas where termites are heavily established. (This might seem high, but considering homes last 100’s of years, 20% isn’t too high). In most of these cases the termites will enter through wood that is touching or buried in the soil. Termites cannot see so they rely on their sense of smell to find food sources. Termite colonies begin when a male (king) and female (queen) fly from the colony and join together to form a new colony. The female can live for decades and produce thousands of eggs daily. The king and queen require the worker termites to feed and care for them. For colony protection, the termites produce soldier termites, whose job is to protect the colony from attackers. The workers will construct elaborate mud tunnels hundreds of feet long several feet below the soil surface, this allows their environment to stay humid as they search for food. If breaching the soil surface, mud tunnels will be constructed from the soil to the food source to ensure that the environment stays suitable to the termites. Subterranean termites are not able to travel outside these mud tunnels for long as they need to stay in a moist environment to survive.

Does the increased moisture in the soil from mulch attract termites?

If termites require moisture, it is reasonable to expect that mulches, which prevent evaporation from the soil and increase soil moisture would cause create a better environment for termites. However, studies have been done to see if termites are are more prevalent under wood mulches vs. gravel vs. bare soil. The study found that when comparing mulches, subterranean termites were not more likely to be found under a wood mulch vs. bare soil. Surprisingly sustained activity was significantly higher under the gravel mulch. In retrospect this makes sense, considering that the termites establish themselves deep in the soil where the soil stays moist. If the foragers find a food source they will connect their mud tunnel network to the wood at the surface. Therefore increased surface moisture is not needed for a termite population to survive. I suppose the best way to deter termites would be to stop watering your landscape entirely, and try to dry the soil several feet deep…but that doesn’t seem productive to my farming goals.

Does mulch act as a food source for termites?

Termites are fairly picky eaters, they mainly enjoy softwoods, and large portion sizes. Although in lab conditions certain types of mulches (softwoods) will be consumed by termites in sufficient quantities to sustain themselves, it has been confirmed that in natural settings, termites will continue to look for the best food source, and the colony will abandon less desirable food sources for better ones. Finely chipped mulch is likely to be too labor intensive for termites to consume. There are plenty of other better sources for the termites to munch on. Also in laboratory studies, hardwood mulches were not readily consumed and termite populations diminished when their food source was limited to only these mulches. I would expect that if mulches were a desirable food source, raking through an organic mulch would be teaming with thousands of termites, and their associated mud tunnel networks. This however is not the case.

What about natural predators?

There are three main natural predators of termites. Ants, spiders, and nematodes. None are able to provide complete control of your termite problem. Ants will attack termites and carry off their eggs and small workers which can limit their population. This is likely to occur when ant food sources are scarce. Even though this action is beneficial, the negatives for me outweigh the positives and I still recommend controlling your ant problem by using the steps listed here. Spiders can help prevent some queens and kings once they take flight and leave the safety of their underground nest, but this effect is limited. Nematodes could potentially wipe out a termite colony as they infect individual termites and them eat them from the inside. They can then multiply and move to other termites in the colony. Several species of nematodes are needed, as certain nematodes are effective against specific types of termites, and ineffective against others. The issue has been that while some lab tests have been successful, field studies in real world situations have not provided adequate control of termites. Interestingly termites seem to be able to sense certain strains of nematodes and will avoid the area where they were applied. Beneficial nematodes attack other types of pests in your garden and are used successfully as a natural control. You can find the list of pests that they control here.

What can I do to prevent termite infestations?

Fortunately there are some simple steps you can take to limit your exposure to termite damage. None of these are 100% effective at preventing termites, but reduce your chances of infestation and/or make detection easier.

  1. Make sure wood does not contact the ground. Pull soil and mulch back from the foundation so that termite tunnels are easily seen.
  2. Monitor the foundation for termite tunnels. If found early, damage is minimized as it generally takes years for significant damage to occur.
  3. Seal any cracks or entry points on the exterior of the house.
  4. Repair leaking faucets and reduce irrigation around the foundation of the house.
  5. Don’t store large food sources life firewood, or lumber near the foundation, and keep it off the ground.
  6. Use finely ground mulch (I prefer Kellogg garden soil or Forest Floor from Aguinaga Green as a mulch), this is preferred anyway as it is better for your garden and it breaks down faster releasing nutrients for your plants to use.
  7. Apply borates such as Tim-Bor, to exposed and untreated wood or as a powder to entry points into your house.
  8. Try the DIY bait suggestion below.

Professional & DIY Treatments

If you decide to apply some sort of active control, the research shows that baits are an effective long term solution by eliminating the colony. Barriers work ok, but the best barriers and poisons are toxic and have been outlawed by the EPA. Barriers will fade in time, and do not eliminate the colony, just discourage a certain access point. The best and most effective baits on the market contain either hexaflumuron (older formulation and well established…available for DIY from HHexPro Termite Monitoring Baiting System 10 stations no baitexPro which sells the baits and stakes) or noviflumaron (latest and greatest..and most expensive since they are only sold to professionals although you can find it on ebay).  Both have effectiveness in the high 90th percentile in real world applications (Other termite baits are on the market and cost less, but real world testing, summarized in the research above, has not shown them to be effective on their own). The baits work by preventing the workers from molting, this effectively kills off the workers. Without the workers the colony can’t get enough food to support itself and it dies. You will need to place the stakes about every 10 ft. away from your house but forming a complete perimeter. This method has high upfront costs, and require monthly monitoring of the traps. It is surprising to me how expensive the stakes are. I would suggest you make your own bait stations relatively cheaply using PVC pipe, and use cut up pine or other very softwood as the pre-bait material. The baits would still have to be purchased, but you could reduce your up front costs significantly. If you decide to bait yourself make sure you follow these steps to make sure that the baiting is the most effective:

  1. Make sure to monitor the pre-bait monthly. Some Gatorade or other sugary sports drink has been effective to make the baits more desirable.
  2. Once termites are discovered in a pre-bait replace the bait with the actual poison control baits.
  3. Now you need to trick the termite colony into thinking this area is the find of the century so they invite more termites to the dinner! Add several other bait stations to the area. Some, if not all, should include the pre-bait. You may want to start out with pre-bait in all and switch once the bait is found. (This is because the termites mark the tunnel to the food source with pheromones, the stronger the pheromones, the better the food source. Also if too much poison is added too quickly, you could wipe out the workers before the poison is shared with the rest of the colony)
  4. Continue to monitor but don’t disturb the termites, once they have stopped feeding you can remove the poison control baits and put back the pre-bait for monitoring.

Closing thoughts

There is little evidence that wood mulch has much if any impact on increasing termite populations around your home. Whereas having the soil level too high against your house, or having wood exposed and near the soil has an overwhelming body of evidence proving that this can significantly increase your chance of having a termite problem. I would not be hesitant to use a wood mulch in my garden, but follow and practice the simple prevention techniques listed above, such as keeping it away from the foundation and limit the watering around the edges of my house. Based on this research I plan to add an annual inspection routine to my calendar, as catching the problem early is the best way to limit the costs. You may even have a friend that worked in termite control and can help teach you how to look and what to look for, or have an inspector out for a free inspection and follow him around and discuss what they are looking at and what they are seeing. If you have had a problem in the past or find termites around your house, the DIY or professional baiting solution may make sense to eliminate the colony and provide some long term control.

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