The End (hopefully) of Molasses Malarkey

I’ve been discussing the purported insecticidal properties of molasses in my last couple of posts. I’m hoping this will be the final nail in the coffin (or stopper in the bottle):

Here’s the end of the original blog piece linked above:

“Microbial bloom and Fire Ants
“These two things seem unrelated. Microbes and specifically bacteria consume simple sugars (which is why your momma made you brush your teeth). When soil born microbes are exposed to simple sugars, their numbers can double in just 30 minutes. As microbes go through their life cycle, they add organic matter and micro nutrients to the soil, improving the soil and making nutrients more available to your plants. Regularly applying molasses to your soil and plants greatly improves the quality of the soil over time. Soils with high microbial activity are easier to dig in and stay moist longer.”

I’m actually going to leave this paragraph alone, since it’s relatively accurate (except for the sentence about applying molasses to your plants, which I dealt with in my first post). Let’s move on:

“So, about the Fire Ants…since it seems that the big universities can’t make money studying the effects of molasses on Fire Ants…they don’t do any research on the subject. But, it has been proven that molasses makes Fire Ants pack up their mound and migrate to your neighbor’s yard. It may be that the bloom of microbes, irritates the little stinkers. It could be that they are running from a specific microbe. It could be that they just hate sugar (they eat mostly protein which is why you can turn a greasy over baked pan upside down over a Fire Ant mound and they will clean it for you). What ever the reason, applying molasses to your yard makes them leave.”

This entire paragraph is nonsense, beginning with equating grease with protein (it’s a fat) and ending with the supposed lack of research on fire ants. There’s a LOT of research on fire ants; pest studies are very well funded. Out of the 1500+ articles I pulled up on fire ants in the Agricola database, only one includes molasses. And that’s in a 1986 study comparing different kinds of baits (“Comparison of baits for monitoring foraging activity of the red imported fire ant (Hymenoptera: Formicidae)”), where molasses was found to be more attractive to fire ants than peanut oil. How this translates to “molasses makes Fire Ants pack up their mound and migrate to your neighbor’s yard” I’m not quite sure.

“If you’re crunched for time and money, molasses is the answer to a lot of your gardening problems. The benefits are undeniable, your yard will smell great and you get to feel good about letting your kids and pets play in the yard. Whether you choose dry molasses (applied to soy chaff) or the liquid (which is cheaper to use), molasses is the single best thing you can do for your soil and plants.”

The typical snake-oil pitch! (For a completely unrelated but accurate and amusing example of an old-time snake-oil pitch, check this link. You’ll see the similarities).

“It was brought to my attention that I forgot to add this info. (It is hard to remember everything when you are trying to rule the world!) During moquito weather mix:

  • 3 tbsp molasses
  • 1 tbsp Liquid Garlic (a deterent and has some fungicidal properties)
  • 1 tbsp liquid organic fertilizer of your choice (seaweed, fish emulsion, etc) into 1 gallon of water

Spray with abandon, every week if necessary but it may last up to 2 weeks if we don’t get much rain. This also works like a charm on lace bugs on azaleas and lantana.”

Spray with abandon???? This has to be one of the most reckless pieces of advice I’ve ever read. Whether it’s a fertilizer or (more importantly) a pesticide, it should *never* be applied lavishly. (Though this is such a dilute solution that it probably isn’t much different than water.)

This topic has made me crave the molasses popcorn balls my grandmother used to make. Anyone have a recipe for those?

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Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - "The Garden Professors" Facebook group - Books:

22 thoughts on “The End (hopefully) of Molasses Malarkey”

  1. “Spray with abandon???? This has to be one of the most reckless pieces of advice I’ve ever read……it should *never* be applied lavishly. OK, so I’m in the shower early yesterday morning thinking about this article. The concept of molasses being the end all product in gardening really has me intrigued. Then I look down at my feet only to see a brown marmarated stink bug crawling around also enjoying the warm water. I give him a flick out of the way into the corner of the stall with my toe only to see him head straight back toward the center. I do it again…. same result. I really don’t want to crush the the little guy. (big Stinker) Now I’m thinking, ‘wow, I wish I had some molasses handy.’ But alas none in sight. Then I spot the shampoo bottle and quickly, with our thinking squeeze out a little glob on the bug figuring it might slow him down till I get done. He takes about 3 steps and I’m thinking… ok no breakout discovery here, then he stops dead in his tracks. I mean DEAD! WOW!!! ‘This is the greatest stuff since molasses.’ So Inow I’m thinking how I can turn this discovery into a garden products empire when it dawns on me damn,I just put this poison on my head (not really much hair there). shucks bring on the shoofly pie, its bound to be a good wormer.

  2. Hi Linda,
    I don’t use molasses or recommend their use. I also know the difference between an observation and a scientific experiment. Still, let me share an observation. About 10 years ago somebody gave me some molasses to experiement with. I used them in the vegetable garden on several crops with no observable results. I also have a peach orchard consisting of 12 rows running east and west with 15 to 19 trees in each row. The trees are planted even with each other which creates north and south rows. My peach varieties and all of my cultural practices such as spraying, fertilizing and even thinning go in an east and west direction. I used some of the molasses in a backpack sprayer on the peach orchard and sprayed it on a north-south row. I then skipped a row and came back. This gave me 24 sprayed trees adjacent to 24 unsprayed trees. This was the only thing I ever did in a north south direction. I saw no difference that year. However the next summer at harvest, peaches from the sprayed trees were almost free of catfacing (caused by stink bug damage in early spring) while there was lots of catfacing damage on the unsprayed trees. I wasn’t looking for this result, so I had already harvested some of the peaches before I noticed it. Once I noticed this pattern on my first varieties, I closely examined about 10 side by side sets of sprayed and unsprayed trees. It was very obvious that the sprayed trees had less damage. (Yep I did the examination myself. No sense in trying to make it scientific at that point.) I couldn’t some up with any reasonable theory of why this happened. So rather than attempting to duplicate those results, I just tightened up on my regular spray program and didn’t have significant catfacing damage as long as thiodan was legal. Now that thiodan is off the market and stink bug pressure is rising, I am in a little bit of a quandry. I am hesitant to put out money attempting to duplicate something that makes no sense to me. On the other hand, I know something happened because I was there when it happened.

    1. Hi David –

      It’s an interesting observation…as you say, you don’t want to spend a lot of money chasing a phantom. But I want to look at what you did more closely.

      You sprayed leaves and fruit (I assume?) and saw no difference. The following year, though, you had less insect damage (just to fruit, not leaves) on the sprayed trees. Do I have that right?

      Assuming it’s correct, then we know the molasses itself had nothing to do *directly* with the decrease in insect damage (in terms of still being on the tree, because it would be long gone by the following spring). What I would need to know is what stink bug life history is. Do they overwinter on the tree? If so, it’s possible that molasses may have affected egg laying or something else that resulted in a decrease of stink bugs.

      The more you can tell me, the better for trying to figure out what happened. Because I do believe you – we just have to figure out some other variables first.

  3. When I lived in Dallas I had terrible problem with fire ants. I hired an organic lawn care company. The lawn in general was healthier quickly under their regimen, but I still had fire ants. One or two applications of dry molasses on and around the hills and the ants were gone, never to return. Scoff all you want. I worked in a hospital research office and learned that if research isn’t done on a very specific topic, then “the research doesn’t prove” whatever. Not because it’s not effect, but because it wasn’t studied. Also, often research is financed by Company A to “prove” that a remedy that doesn’t use their product doesn’t work. The research may be badly done, but it “proves” something. You can’t trust that just because something is published in a peer-reviewed journal that it is really true; the old-boy network does often work to protect old ideas.

    1. Hi Hanna –
      Since you worked in a research office I’m surprised you don’t know that you don’t “prove” anything with research. You either find evidence to support a hypothesis or you disprove it.
      You may be interested in reading about pseudoscience. One of the characteristics of those who promote pseudoscience is an “Assertion of claims of a conspiracy on the part of the scientific community to suppress the results.” (
      Peer review is the best tool we have to evaluate science. It’s not perfect, to be sure. But proponents of practices or products either have to meet this standard or they have to accept that their belief is not supported scientifically. In this case, they shouldn’t use the trappings of science to give their product or practice the patina of evidence-based information.

  4. She didn’t say there wasn’t any research on fire ants; she said there wasn’t any research on “the effects of molasses on Fire Ants.” Since you only found one ant study out of 1500+ that even mentioned molasses, it seems this statement is not nonsense, but largely accurate. I too prefer peer reviewed studies to anecdotes, but given the attention from gardeners to the topic (Googling “ants molasses” yields 250k hits) you’d think somebody else might have looked into the effects of molasses on ants in the last 30 years.

  5. Im a simple gardner, have been since forever. My observations of molassis is, simply wonderful. My best result is on my lawn, had a patch that always looked like it needed a water, seaweed solution, iron, ever tested the soil pH and found it a bit high, added some sulpher, still, needs a water. On a whim, used some molassis i had for nematoad control, now that patch is the lushest of all. Imo in the right place, most excellent.

  6. Has any one ever stopped to think that its all about the bacteria. I believe I in theory have figured out through research and a little bit of logic that its the bacteria. If you where to use a aerated compost tea that you fed with molasses you would probably get even more amazing results than just using molasses. And that is whether you spray it on your plants or feed it to the roots. However having a diverse bacterial and fungal content is probably not appealing to pests. I understand that an aerated compost tea should not have pathogenic bacteria however i am more under the assumption that would be towards humans. However is it not completely possible that the bacteria could possibly be pathogenic to the bugs. However spraying your plants with molasses would greatly increase the amount of bacteria on the tree. This might also explain why you see more ant infestations in “nice” “lush” city yards. The city yards most of which probably worst effected by ants probably have a terrible bacterial diversity from over fertilization and over irrigation and no organic additives ever. Boom there you go!

  7. I want to put molasses on tree cutter ants in the hope they will go elsewhere. Nothing kills them except diesel.
    Think it may work?

  8. I fully recognize that this is anecdotal, but I’ve had success with molasses repelling fire ants. The two years I used it, I had very few mounds in those areas. The following year, I didn’t use it, and they were back. Twice I’ve used it in the compost pile and the ants leave. It may cause the pile to heat up more so they leave due to the change. Though my compost thermometer didn’t show a spike in the temp. As you stated, there is not any science to support this, but dry molasses has allowed me to have a yard with less fire ants in it. It may not be a direct repellent but I am happy with the chain reaction it sets off.

    1. Without some sort of control (i.e., part of your landscape NOT treated) there is no way to determine what the causative agent was. If it had consistently reliable effects you can be sure the results would have been published and products registered for legal use as a pesticide.

  9. Hi, Linda;

    Could you let your Lane County Extension Service know about all this? They just sent a customer to my garden supply shop looking for “horticultural molasses” because, according to the customer, they agreed with the “science” she presented that the carbon in the carbohydrates would smother broad leaf weeds by starving them of nitrogen. I tried to explain what molasses would actually do to microbial life and what microbes do to nitrogen, but she refused to listen because “the extension service would have told me that.”


    1. Hi Abraham –
      You would need to contact Oregon State University, since they are in charge of the Extension program in Oregon. (I’m in Washington state.) The state coordinator of the Master Gardeners is Gail Langellotto. Her speciality is entomology but she’s responsible for horticulture content as well for all the county offices.

  10. I have a much better idea than putting molasses, or milk, or things like, that on plants. Instead, we should chop up dollar bills — as finely as possible — and use that as mulch. There are minerals in the paper and inks that do wonders for plant nutrition. And, I suspect that $100 bills will be even more effective than singles!

    1. No – there isn’t any proposed mechanism by which it could kill plants. There would have to be some sort of hypothesized mode of action, and I can’t think of any. More importantly, it’s not labeled as a pesticide of any sort and shouldn’t be used as one.

  11. Interesting article, and you seem well qualified in the field (pun intended).
    However, I wonder if you missed something….
    So, I know that Bayer Cropsciences is selling different microbes (bacillus subtillus, for example) as an anti fungal agent, and others sell other bacteria to kill caterpillars and worms ( and I have used them with cabbage moth worms, and they work), and I wonder if the mechanism of the action of molasses is to stimulate the growth of microorganisms that naturally act as insecticides or anti fungal agents? If so, then the ‘malarkey’ of molasses isn’t such malarkey after all….
    Me thinks someone should do a bit more studying ‘in their field’…ehh, Dr.!?!?

    1. Well, that’s an entirely different question than a direct mode of action. Yes, carbohydrate sources feed microbes; that’s well established. And some microbes do have insecticidal properties. But you don’t just dump molasses on the ground and assume that the microbes present (whatever they are) will somehow kill pest insects (whatever they are). That takes research, time, and money.

      Feel free to fund such research. There are lots of researchers who would be interested in pursuing natural pest controls.

      1. Whether a direct mode of action or the result of competition for resources, the result is still the same: fewer pests.
        And you are right, that research should be done. But, until that research is done, it is both unfair and irresponsible of you as an authority on agricultural methods to call something ‘malarkey’ when the reality is that you really don’t know. The research doesn’t support your position, nor does it support the other position (except anecdotally), so in this instance, your silence on the subject would be eloquent.

        1. There is no research supporting the use of molasses to kill insects. It’s not the job of scientists to disprove claims – it’s up to the proponents to demonstrate efficacy through controlled, peer-reviewed research and publication. That’s how science works. (See Russell’s teapot online for the guiding philosophy.)

          Proponents can’t come up with a cogent explanation of how molasses directly kills insects. If there was a logical, theoretical mode of action, you can be sure it would be explored by researchers. There’s a lot of money to be made in discovering natural pesticides.

          I did a quick search through recent publications on this topic since it’s been a few years since I posted this column. There is a recent article (2021) in the Journal of Applied Entomology that includes molasses as the bait for insecticidal sprays – in other words, it’s added to the active ingredient to stimulate consumption by the insect. They also used straight molasses as a spray, presumably to see if there was any direct control. Not surprisingly, this treatment resulted in the greatest survival of the pest (in this case Drosophila suzukii).

          Google Scholar allows anyone to find these sorts of articles.

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