How insects sense unhealthy plants

Plants constantly communicate with electromagnetic signals, and insects are tuned in to some of those signals. In the excerpt of our podcast interview, Tom Dykstra describes how insects are attracted to some plants and not to others. If you want to learn more about this fascinating topic, or have any questions,  Tom is presenting a webinar on Leaf Brix and Insect Herbivory tomorrow at 1 PM EDT. Please join us.

John: This is a fascinating piece, Tom. I know that this is something that many growers are very interested in and want to understand much better. Would you be willing and able to dig a little bit deeper into describing how the olfactory senses work and why some insects are attracted to certain regions where others are not?

Tom: Generally, the insects are smelling with their antenna and with their palps, which are some of the mouth parts. So when they’re flying through the air, they pick up various odorants in the air. And these odorants are vibrating and giving off energy. They’re absorbing and emitting energy constantly. As long as they are above zero degrees Kelvin, which is absolute zero, they are vibrating.

And these electromagnetic vibrations can be easily detected by various equipment in the laboratory, as well as the equipment on an insect. They have various sensilla. I would call them tiny antenna on the actual antenna-proper of the insect. And it’s these antenna—whether it be the antenna-proper or whether it be the smaller sensilla on the insect—that are tuned into very particular frequencies. And these particular frequencies are all important for the particular insect.

Some insects would not be tuned into CO2. They would have no reason to be. Whereas other insects, like mosquitoes, would be tuned into CO2. There are certain floral compounds given off by plants that some insects are going to be attracted to—honeybees being prominent among them. And then you have certain scents that are not attractive at all because some insects don’t go after flowers. There are some plants that advertise themselves as unhealthy. And when they do so, they are picked up by other insects.

Insects are only tuned in to the unhealthy plant. No insect will ever attack a healthy plant. What they’re zooming in on is the unhealthy plant, because it’s digestible. Healthy plants are not digestible. Unhealthy plants are. Because they can’t digest a healthy plant, there’s no interest in even attacking it. It either has to be injured or it has to be unhealthy. And then, by doing so, it is now digestible, and this is what an insect is going to attack.

At the beginning of our conversation, I mentioned how once you get above twelve Brix, insects really aren’t causing any more issues with your plants. And once you get above fourteen, they’re really not even landing on your plant, unless they just want to rest on it, because they won’t be able to take a bite. Or if they do take a bite, they won’t be able to get through the cuticle or into the phloem tissue—it’s not going to be digestible to them. They’ll have to pull out and move on to a different source.

So all insects are flying above, looking for crop plants that are digestible to them. Plants advertise themselves as being unhealthy, essentially saying, “I’m unhealthy. Please come eat me.” And so the insect will come in and it will start eating the plant, because that’s their job.

Our job is to eat healthy plants. We have a much more elaborate enzyme system. Our digestive systems are designed to eat healthy food. We don’t do well eating Doritos all the time. We do well when we eat healthy plants, and this leads us to be healthy.

For the insect, it’s different. Insects do not do well on healthy plants. They can starve. You can take a Colorado potato beetle and put it on a healthy potato plant and it will not be able to eat it. But you can take an unhealthy potato plant and the Colorado potato beetle will go to town, because this is what it is meant to do. And so because insects are only attracted to unhealthy plants, the unhealthy plants will advertise themselves. They’ve got certain visible frequencies that insects can detect, especially from a distance. And they’ve got certain odors. And these odors can be picked up by the antenna and by the sensilla, and the insect will move in for the kill, so to speak.

John: When we look at plant health, we’re talking about healthy plants versus unhealthy plants. What are some of the compounds that serve as insect attractants that we could manage and monitor?

Tom: You can’t. It would really have to be a general thing. Generally speaking, ethanol is a universal odorant that advertises itself as being unhealthy. So a lot of the plants will release not just ethanol, but also various alcohol components. Not all alcohols, but many alcohols advertise a plant as being unhealthy; it’s a hallmark of fermentation. Fermentation produces the alcohol.

And so when a plant is degrading and it’s in trouble and it’s fermenting, even in a small way—even in an imperceptible way—it will advertise itself. If these odorants are being released, they will be picked up by insects. It will change how the plants are perceived. You can take satellite images of two crop plants and they look different on various images. It can be a visible image. It can be an infrared image. But they both may be corn. They both may be soybean. They both may be anything you could think of, but they will not have the same look under an infrared camera or under a visible camera.

This is something which is very profound in grasshoppers. You don’t find them so much in the United States, but on other continents, locust swarms are a problem. These locust swarms are not just millions of individuals, but billions—sometimes trillions—of insects. They descend upon a very particular crop and take it all the way down to the roots and then pick up and fly away. And they will leave a farmer’s field right next to that exempt. These are the remarkable things that you realize when you see stuff like this— the grasshoppers made a decision. They made a decision to eat one plant over another. Why? Why didn’t they just come down and eat everything? We’ve always been told that grasshoppers will eat anything, and yet there is direct proof in some of the images that I have seen and testimonies of others that, no—they actually are very selective.

Now, I should tell you that grasshoppers are less selective than other insects. Some insects will disappear by a Brix of eight. Other insects will continue to chew on your plants right up through ten, eleven, or twelve Brix. But once they get to about twelve, they will lose interest. And the grasshoppers are among them. You can find the grasshoppers among slightly healthier plants for that reason, but you’re going to find that with the aphids, the leafhoppers, some of the other hemiptera insects, once the plant gets to eight, they lose interest in the plant. You just won’t find hemiptera insects on a plant above eight Brix. And those are the ones that have the beak that they stick into the phloem tissue and take a sip from the sugar water that is flowing around the phloem tissue.

So every insect has its own cutoff. You really have a lot of insects fall off by the time you get to eight. And as I mentioned at the beginning of this, most of the crops are between four and eight. So a lot of plants are really susceptible to every single insect that is out there. But if you can get above eight, you pretty much can take care of your aphids and your leafhoppers and psyllids. The Asian citrus psyllid is down here in Florida, and other psyllids, because it’s very rare to find a citrus tree that’s above eight. We’ve tested a lot of them.

Managing nutrition for control of aphids and flea beetles

Tom Dykstra and I discussed the concepts of plant health, nutrition management, and insect resistance in a rapid fire, intense one hour webinar, with a specific emphasis on controlling aphids in sugar beets and flea beetles in canola.

While the conversation was fairly high level, and didn’t get into the nuts and bolts of implementation, Tom’s knowledge of insect metabolism and the type of food sources they require to survive is unparalleled.

If you want to learn how to grow insect resistant crops, this webinar is a must listen. You kind find the recording on KindHarvest.ag here.

Tom uses a refractometer as a research tool, and describes a brix index of plant susceptibility to to different groups of insects at different brix levels. There is a big difference between using using brix as a research tool and using it as a crop management tool. You can read my thoughts on using brix here.

Healthy mosquitos don’t vector malaria

When we think about epigenetics and the phrase “environment determines genetic expression”, we should think about what this means not just for the plants and species we are trying to optimize, but also for all the plants, fungus, bacteria, nematodes, and mites commonly called ‘pests’. If environment determines their genetic expression, that means we can manage their virulence or pathogenicity to the degree we can manage the environmental factors they depend on.

Tom Dykstra shares an interesting perspective on healthy vs unhealthy mosquitos, and their capacity to resist infection from malaria or other ‘pathogens’.

John: You and I have discussed before how environment determines genetic expression. And you expressed that you have had difficulties infecting some mosquitoes with malaria. As we’ve been having this conversation about mosquitoes, that popped back into my mind. What are the differences between healthy and unhealthy mosquitoes as vectors of infectious disease?

Tom: Well, I personally have not infected mosquitoes with malaria, but I’ve talked to researchers who’ve worked on this. Let me put it this way. Most Anopheles mosquitoes do not transmit malaria. Most Aedes mosquitoes do not transmit dengue, yellow fever, or Zika. Most Culex mosquitoes do not transmit encephalitis.

When you observe this, you understand that not all insects are infected with the disease. So you can get bitten by thousands and thousands of Anopheles mosquitoes and not get malaria. But all you have to do is be bitten by one mosquito that does have malaria in order for you to get it.

And this is one of the truths of biology that has been revealed to us—that insects also have various states of health and lack of health. In order for them to be relatively healthy, they need digested components. Their food sources need to be as such. But if their food source is not that good, or if it’s missing something, they can suffer. Insects have died in the field. I’ve seen it many times. Sometimes people try to keep them as pets and they die. We see them dying in the field all the time. They are susceptible to disease. They also have states of health and lack of health that are somewhat analogous to what you would find in a human.

If you’re working with mosquitoes in the laboratory, and you try and infect them with the particular disease that they’re supposed to be infected with—Anopheles mosquitoes with malaria, for example—you will not get a 100 percent infection rate. And that is amazing. This is in part because when you’re raising them in the laboratory, they’re coddled. They’re given everything they need. Therefore, they’re in pretty good shape, and it becomes a little difficult to infect them. Out in the field, they might be more susceptible. Ones that are more susceptible might die. Others would be more susceptible to actually getting a disease—like the malaria protozoan or the Zika virus or anything of that sort. And it can actually take hold of the system, because the insect doesn’t have the immune system to take care of it. It kind of sets up shop inside the insect. 

2020-07-27T19:35:50-05:00July 28th, 2020|Tags: , |

Unhealthy people attract mosquitos, just like unhealthy plants attract other insects

Insects will only eat that which is digestible to their system.

From the interview with Tom Dykstra:

John: I have friends who will attract every mosquito for dozens of yards around, and others who, for all practical purposes, are mosquito-immune. Can you describe the differences?

Tom: I hate saying this, but that is the difference between healthy people and unhealthy people. If you have digestible blood, the insect can use your blood. If you have healthy blood, the insect is not attracted to it. Does this mean you’re healthy all the time? No. People have certain states of healthiness and unhealthiness. But as long as your blood is digestible, it’s going to be attractive to an insect.

It’s the digestive system. Insects do not have very good digestive systems. Stuff has to come in digested to them because they cannot digest things. They just don’t have the enzymes. They’re garbage collectors. They eat muck. They eat garbage. They eat bad stuff. They eat stuff that we don’t want to eat. Take a look at cockroaches, for example, or fruit flies. They’re always around decaying fruit. They’re not around healthy fruit. These insects that are keying in on very specific plants. Or even, let’s say, the fruiting structures of a tomato—that’s what they are keying in on.

Mosquitoes need something that’s digestible. When they take a blood meal, it must be incorporated through the process of vitellogenesis: taking those nutrients in your blood and incorporating them into an egg. This occurs in about twenty-four hours—very, very quickly. So if they’re not getting digestible blood, they cannot, through the process of vitellogenesis, take those nutrients and feed their eggs. And that’s a problem, because obviously the mosquito wants to feed its egg. The only reason it takes a blood meal is to feed its eggs.

We do have these differences among individuals. Some are just more digestible than others, and they’re going to be more attractive. Grasshoppers have a choice as to what crop they eat, and mosquitoes have a choice as to what blood meal they wish to get. Through their antenna and all of their senses, they detect that someone is more digestible than another, and they’re going to go after that individual. Even though that may offend some people, I do feel an obligation to tell the truth the way that I know it, according to the information that has been given to me for the past twenty to thirty years of my life studying insects.

John: I very much doubt that you’re offending people. I would say that you’re simply communicating some very intriguing ideas that many of us have observed to be true in real life and have wondered about the differences. So thank you for sharing that.

Tom: I’m happy to do so. When you go to the supermarket and you see fruit flies flying around the tomatoes, some people think, “Oh, I don’t want these tomatoes—they have fruit flies in them.” But honestly, all you have to do is find that one tomato near the bottom that’s injured, and that’s where all the fruit flies are located—near the one that’s unhealthy. And that essentially equates to that which is digestible. A tomato that is degrading—that is decomposing—is being broken down. And when it’s being broken down, it’s digestible. Insects will only eat that which is digestible to their system.

2020-06-23T14:38:59-05:00July 2nd, 2020|Tags: , , |

Electrical conductivity comes from biology in healthy soil

The agronomy of the future will be based on measuring and managing the biophysics of soil and organisms rather than focusing on chemistry and genetics. Important parameters to manage will include soil electrical conductivity, paramagnetism, redox, and pH, from a perspective of managing electron and proton flow through the ecosystem.

To grow crops that are high yielding and healthy, soils need a minimum electrical conductivity of 200 uS at germination, gradually increasing to 600-800 uS during the fruit fill period. Plants don’t grow from nutrients. They grow from the energy that is provided by those nutrients. Mainstream agriculture provides the electrical conductivity in soils by adding ionic ‘salt’ fertilizers that have a high EC, and thus increase soil EC. Of course, these ionic salt fertilizers oxidize the microbial population, age clay, and damage soil aggregates.

In biological soils, the electrical conductivity should not come from ionic nutrients held in the water solution, but from microbial cells. This is much more advantageous to the crop, because EC levels are sustained through the entire growing season, and do not drop off as soon as soil water becomes limited. Soil biology can provide an abundance of electron flow through the soil, and produce much higher yielding and higher quality crops than we consider ‘normal’ today.

Here is an excerpt from the podcast interview with Tom Dykstra where he alludes to this function of soil biology.

Tom Dykstra:

Now, when these microbes are gone, they are no longer able to hold on to the energy that is in their bodies. And so you have now given up a massive energy source. This is where the electromagnetics comes in: if you do not have those microbes, there is no energy in the soil. Each microbe is about half a volt of sequestered energy. This doesn’t mean that there is this massive amount of energy—that if you stepped on some ground with millions of microbes, it would blow your foot off or catapult you into the air fifteen feet. What this means is that this is clean, stored energy that’s found in the membranes. It’s found in the chloroplast, in the endoplasmic reticulum. 

Everything that is inside the cell has a nice, clean storage form of this energy, and that energy is then made available to the plant, either directly or indirectly. Sometimes the plant can use the nutrients if the microbe dies. Microbes are dying all the time, and some of their nutrients can be taken up by the plant, because everything is bioavailable when a microbe dies. Or you can have a more indirect result—when the microbe is actually releasing minerals to the plants. These microbes can break down minerals far more efficiently than plants. Without these microbes, the plant is no longer able to take in minerals. And these minerals are the constituents—the cofactors—that are used to keep photosynthesis going. Without these minerals, photosynthesis suffers, and we see lower Brix.


2020-06-23T10:54:02-05:00June 25th, 2020|Tags: , |

Insects are only attracted to unhealthy plants

An excerpt from the podcast interview with Tom Dykstra:

John: What do you believe to be true about modern agriculture that other people may not believe to be true?

Tom: Insects are only attracted to unhealthy plants.

If you believe that insects are attracted to unhealthy plants, your whole thinking changes on insects. Suddenly you have no use for insecticides. It just follows with that level of thinking, because you realize, “Well, I’m not competing with insects. They’re just eating some of the garbage plants that I shouldn’t be eating. So I really don’t need to spray them anymore.”

So now all the organophosphates and synthetic pyrethroids and carbamates and neonicotinoids—they’re all unnecessary. As you reason through this, that’s one of the conclusions you come to. You have to come to it when you believe that insects are only attracted to unhealthy plants. I don’t even have to come out as an anti-pesticide guy. I can simply say that insects are not attracted to unhealthy plants. And by extension, I would say, yes—insecticides are unnecessary.

Under specific circumstances, they have their role. I will be the first to admit that I’ve had fire ants. Sometimes they come into the house. I do have a Raid can in my house. And we have had situations where the kids would leave food crumbs around. And the situation has to be taken care of. So I’m not afraid to use insecticides, and I understand that they have their place.

However, having said that, when I’m raising crops I’m never spraying it with anything.  I don’t have a knowledge of all the insecticides, but I don’t use any of them. I’m not using any herbicides or fungicides. I use insects as indicators. I go out and check my corn plants, for example, and I look to see if they’re being attacked. And if they are, I determine what insect is attacking them, and I figure out why they aren’t healthy.

For example, the first time I started planting corn, I did have a few insects that were attacking it. By the third time that I was planting corn, no insects were attacking it, but deer came in and cleaned me out. This is the difference between the insect digestive system and the mammalian digestive system: we have a higher-level digestive system. We can handle healthy food. The deer are more interested in healthy crops. They’re not going to go after unhealthy stuff. They’ll leave that up to the insects.

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