This afternoon we have the privilege of speaking with Dr. Tom Dykstra, the renowned entomologist who's been making waves in the Ag scene with research on the correlation between Brix levels and whether or not an insect will attack a plant.

First, do you want to talk about your academic background, how you got into this subject, and why you moved from the university to strike out on your own?

Sure. I started at Cornell University because I grew up in Rochester, New York. It was two hours away and they had entomology. After four years I realized I hated the cold, so I moved down to Florida and then got my master's and my PhD down here. Once I had the academics behind me, I had the opportunity to start an independent laboratory right from the get-go. About a year before I even graduated, which was in December of 1997, I got an offer to begin an independent laboratory from a venture capitalist who wanted to go in a particular direction. It's separate from academia and from the USDA, which is traditionally where most of the entomologists are found. There are lots of industrial entomologists out there. I'm just a little bit different in that I’m not being paid by a large corporation. I get payments from various individuals and companies who are looking for a consultant who is able to speak his mind, who is not bought by the system. I often find myself doing research, which is off the beaten path from what many entomologists do, which is probably why I'm talking to you right now.

Your research is being adapted very practically by people in agriculture. As I understand it, you’re known for the claim that insects will not attack healthy plants: that if you can get your plants to be healthy enough, if they will repel the insects, the insects won't consider those plants to be their food source. Can you just give us a little overview where that claim is coming from and how you tested it?

The idea was not my own. This was started mostly by Carey Reams back in the 60s, looking at plant tissue with a Brix refractometer and taking the initial measurements. He was looking at different parts of the plant and came up with charts. These charts included stems, fruit and leaves, and then he would have a ranking of low, medium, and high.

I was first approached at a conference, I think it was about maybe 1998. All the talk about Brix revolved around the magic number of 12. If you had something above 12 Brix, you're in good shape. No insects were going to attack it and below that, insects will attack. I thought to myself, there's got to be more to it than this, there can't just be a single number. This is not adequate for a scientist.

So I picked up the refractometer, started doing testing, and found out that there were rankings, so to speak, of Brix levels, and insects being observed on plants. Twelve is still a pretty good number to use as a point when insects are no longer attacking it, but I've now picked up on the fact that we need to be about 14 Brix. About 99% of plants on Earth are between 8 and 18, and most them are not attacked by insects, but many plants, especially crop plants, are attacked in the range of 2 to 10.

When my chart came out, it got a certain amount of attention because I was able to take that rule that everything changes at the level of twelve Brix to the next level. What's the difference between 11 Brix and 9 Brix? What happens at 6 Brix? What happens when we get to 7 Brix? This chart enabled me to add more detail to what is already known.

I didn’t want to make this purely academic, having lots of complex charts, complex graphs, regression lines, R-squared values. I wanted something accessible to everyone, using an instrument that was inexpensive and easily available. My first presentation on this subject was 2012, so it's a relatively recent development, but I’ve been looking at this heavily for about 12 plus years, accumulating data. When I spoke in 2012, things really started to take off.

If we back up just a little bit, what is a Brix measurement, and how is that correlated to plant health? How do we know that a plant is healthier by the level of Brix that you're reading?

That's a good question. It has to do with photosynthesis, the making of sugar. All plants photosynthesize, but some of them photosynthesize well and some don't. If they are photosynthesizing well, they're making more sugar. There is an easy way to measure the total dissolved solids in a plant, which is predominantly sugar. There are other dissolved solids, so it’s not quite accurate to talk about it as just a measure of dissolved sugar, but it's good enough. Anytime I'm talking to a farmer, we'll talk in terms of sugar levels. We're investigating how healthy the plant is by measuring how much sugar is produced. We find that healthy plants have a higher Brix level, and unhealthy plants have much lower Brix levels.

It’s measured with a refractometer, which works by passing light through a prism, and the light bends according to the total dissolved solids, predominantly sugar. If it's a manual refractometer, you hold it up to the light and you'll see a line between the white and the blue. A digital one will give you a readout on a screen. The manual is cheaper, the digital is easier to use. A manual refractometer could be less than $20 on Amazon, the digital ones over $100. It’s an inexpensive piece of equipment that we can use as farmers to discern the health of our plants, and I think that's why it was so adopted quickly. I understand it’s taken off not just in the United States, but around the world.

Excellent. But if we just bring this back to insects for a second, why is it that they're targeting less healthy plants and not healthier plants?

They're going after less healthy plants because they do not have the digestive enzymes to break down a healthy plant. A healthy plant is going to have well-formed proteins which cannot be digested as food source by the insect. A plant that can put together proteins and various other sugars like cellulose is relatively impervious to being eaten by an insect. Not so with vertebrates. You and I prefer healthy plants and we can digest them. Deer and many other vertebrates are the same. They all want something that is relatively healthy. The insects do not.

That’s why insects are described as nature's garbage collectors. It’s a term I use, although it's not precise because sometimes insects attack plants that are just a little bit unhealthy, not really garbage. But you do find insects eating plants that you and I wouldn't have difficulty eating it either, even though we might prefer something a little bit tastier, a little bit sweeter. We are looking for the higher Brix plants.

Many people often assume that it has everything to do with sugar, but actually most insects can eat 70 Brix - molasses and honey, among other things. Every insect needs sugar and they will take little bits of, for example, nectar. Nectar is one of the most common sugar sources, and it’s usually about 40 Brix. The difference is that they only take little bits of it. If they over-consume that sugar, they will die. The assumption that insects don't like sugar is not accurate, We are measuring is sugar as a proxy for plant health.

I guess in an agricultural setting, you want pollinators to be attracted to the nectar, but you don't want pests to be attracted to the plant that you're trying to grow and compromise the plant's growth. Farmers will know the specific pests that target their crop, say a potato beetle going after potatoes, they're looking for a certain level of health in that plant. If it's at the level they're looking for, they'll attack it. If it's healthier than what they're looking for, they'll leave it alone, correct?

That is what insects will do. Sometimes though, they will get caught in the middle. The fall webworm female looking for a pecan tree to lay her eggs on will ascertains whether it's healthy or not. If it's unhealthy she goes ahead and lays her eggs on it and the fall webworm will start to make their web and consume the tip of the tree. As they're eating it, the Brix can go up as the tree starts to defend itself using secondary plant metabolites. Then the fall webworm is no longer interested in eating that tree anymore, and you will find all those caterpillars in a clump, sitting there not eating, mere inches away from a healthy pecan leaf. They will remain there for about three days as they eventually starve to death and start falling from the tip of the branch. That's a case where the insect judged it to be unhealthy and turned out to be wrong, and its young never survived to adulthood.

Sometimes the insects can be fooled by this process as I've just outlined, but they have ways of determining whether it's healthy. They can smell it, they can taste it, they can see certain frequencies that emanate from it that tell them when it’s relatively unhealthy and therefore digestible by themselves or their young.

During the life cycle of a plant, especially an annual plant, there'll be a point where it begins to die or to get less healthy. But I assume that while it's bearing its fruit, the plant wants to be at its most healthy and ward off insects most effectively.

That would be correct. During the fruiting stage, insects are usually going after either the fruit itself, or the flower, or the seed, all those reproductive structures. If the seed is very healthy, if the flower is healthy – including the sepal, the petal, the anther, the stamen, as well as the fruits – they will not be attacked. That's why when you're going into reproduction, you want Brix levels as high as you can get, above 14 if possible. Sometimes it doesn't work that way because the levels will go down during the reproductive phase because the tree gets tired because it’s making a lot more proteins. If the tree goes into reproduction at a level of 17.2 Brix, it's going to fare well. If a tree goes into reproduction at 7.1 Brix, it's in trouble because it doesn't have the necessary energy and reserves to produce the fruit, whether it be an orange, an apple, a cherry or seeds. If you're collecting seeds from it, all of those will be compromised. It will become more stressed and more open to insect attack.

We can be more specific about why insects only attack one part of the tree, or why some of them wait until reproduction before they attack while others will attack during the vegetative phase and some can attack during both. The Brix chart is designed to be as simple as possible, but once you start down that path, as farmers start to investigate their own crop, they start to notice some of these nuances as well.

This makes sense for anyone that's ever grown a plant, how in the summer when things start getting drier, the plant is under more stress. If the nutrient reserves aren't there, if the plant can't access enough water, all these stressors combine to make the plant more susceptible. So just when we least want to see insects is often when we do.

Absolutely true.

Let's have a look at that chart now, and if you don’t mind walking us through it the way you typically do when you're presenting it.

Sure. When I'm discussing the chart, I mention that this is leaf Brix. I'm not talking about fruit Brix or stem Brix or root Brix. That’s because leaf Brix is more consistent than fruits roots or a stems. When we're ascertaining plant health, we go after the part of the plant where photosynthesis occurs, where the chloroplasts are located.

The leaf Brix is going to be between 1 to 20. We almost never see it above 20, and the difference between a 20 Brix and 21 or 22 Brix is irrelevant, so I just stop at 20 Brix . Once you're at 20, you've arrived. This is a measure of the total dissolved solids, mainly sugar and mainly sucrose.

We start 1 to 2 Brix. At these levels the plant is extremely unhealthy, and you're not going to find these in nature. They're picked off by insects and disease. We can raise plants in that range as long as they're protected, kept indoors or sprayed with lots of chemicals so that they're not attacked by insects or fungi. The greens on golf courses usually run at 2 Brix and below. House plants, which are taken away from the sun, are often in that 1 to 2 Brix range.

Once we move on to the next category, 3 to 7, these plants can defend themselves because they have what I call a sword and a shield against some insects and some fungi. This is the Brix range we see in crop plants that are raised in our country and some of the other countries.

At the Brix of 6, plant secondary metabolites drastically increase. Plant secondary metabolites give flavor, smell and taste to a plant. It gives you a brighter tomato, a brighter grape. These metabolites start to take off at about 6 and get better as you go to 7 Brix and 8 Brix, but there is a clear demarcation. Below 6 Brix, everything tastes like cardboard. If you've ever had a fruit or vegetable that tastes like cardboard, it’s almost certainly below 6. I have tasted 2 Brix fruits I can't believe the lack of taste. They were white, they had no color and no flavor and I pretty much spit them out.

In next level from 8 to 12, there’s a massive increase in insect resistance. Water retention ability also increases, which is important for Southern California, Arizona, New Mexico, Colorado, any part of the world with very dry conditions. This is because the plant is now putting out root exudates, lots of sugar, folic acids, humic acids, amino acids into the soil, feeding the microbes, and every time these microbes are there, they take a sip of water. So you can reduce your water levels down to 75%, 50%, and in some cases, less than 50% of what you were using.

Once we get above 12, especially above 14, food is being produced. It's what I consider to be fit for human consumption, not for insects, and we have no insects and no disease attacking it.

Then I superimpose some insect groups, usually feeding guilds upon this. The first group is the aphid group, which includes the aphids of course, but I would also include phylloxera and the scale insects among some of the others. This group that doesn’t like high Brix plants at all. They will actively leave a plant when it reaches six or seven Brix, and by the time you get to eight Brix, there are no more insects from this group on the plant.

The more advanced sucking insects, which include lanternflies, stink bugs, leafhoppers, froghoppers and planthoppers, can tolerate plants until it hits about seven Brix and then they have difficulty. At eight Brix, more of them are starting to fall off. By the time you get to nine Brix, you have no sucking insects left on your plant.

Then we move on to the chewing insects, which only leave a plant once it reaches nine, ten or eleven Brix. Then the final group, the grasshopper group, which includes the grasshoppers, katydids and crickets can tolerate higher Brix, closer to the food that you and I would like to be eating.

Now there are certainly nuances, but right now this is more than adequate. Just to give you an idea, we've got over five thousand species of aphids and the list gets even longer when you move to the chewing insects. Because there are so many species, you cannot say that if you reach 7.97 Brix, that you are absolutely not going to have a particular insect anymore. That's why I use a two-Brix range.

There's another version of that graphic as well that has some disturbing info on it. That is, I have observed that GMO crops are very low Brix. They almost never break 10 Brix. Most of the GMO plants are five and below. To give credit where it’s due, I have seen some GMO plants hit 10 Brix, but never in 14, 15, 16, 17, 18 range. I think we scientists were a bit misled because the technology of GMO is so cool, that you can manipulate the genes, remove them, to knock them out. Very cool stuff.

It was all done to make a healthier plant, but now I look at these GMO plants with the refractometer that they're generally less healthy than crop plants, and they are considerably less healthy than 99% of plants on planet earth that are just being fed by the rain and sunshine.

I was taken aback by this. I wasn’t sure I even wanted this information to get out, but my job is to educate even if it’s uncomfortable, so I started inserting this slide into talks. Many people are thankful that I mentioned it, and others are absolutely livid, but the refractometer is not lying to me. I am getting low Brix measurements. When farmers tell me they’re raising a GMO crop and ask how to get it to 14, I have the uncomfortable job of telling them that it's just not going to happen. I have to hit them between the eyes, and many farmers want to be hit between the eyes. They don't want to hear me saying, "I'm not sure. Maybe we could work something out if we did A, B, and C.” They want the truth.

These GMO crops, you're still spraying them, you're exercising rescue chemistry on them, and you still got insects attacking them laying eggs on them. We have every indication that these plants are unhealthy. I see with the refractometer that the crops are indeed very low Brix and this is the reason why insects are still laying eggs on them. Crops that are supposedly genetically protected – like corn plants with European corn borer – still have European corn borers laying eggs on them. The corn borer female doesn't recognize that it's going to die and that it's young are going to die because this corn has a cry protein on it, so it lays eggs anyway.

That's the beauty of this simple device, and when you put that power in the hands of a farmer, their faces just light up. It’s worth it just to see their reactions when they use it for the first time and realize, wow, I've been duped and I need to make some changes.

How can farmers leverage increased Brix levels in their practices, what kind of things can they do? Is it directly tied to microbial life in the soil and to soil health practices?

It is absolutely tied to the microbial health of the soil. Part of the reason the hydroponic industry is not doing that well is because they don't have the soil and they don't have the microbes, and that's why the hydroponic plants are relatively tasteless. I do apologize to the industry. It's very cool what you guys are doing. I love to see the setups, but right now I don't see them producing healthier plants.

Why are microbes important? Because they are putting everything into the roots. The roots alone are not good enough. You cannot put all the nutrients into a soil medium that's been cleaned of microbes, and expect them to get into the plant efficiently. Without efficient nutrient uptake, the plant is not healthy, it's not photosynthesizing well and it's low Brix .

Microbes put micronutrients – manganese, iron, copper – next to the root. The roots put out sugar and various nutrients, feeding the microbes. The microbes pay back by throwing nutrients in the vicinity and work with the plant to get them in there. Fungi are also involved. Some fungi will actually permeate the roots, actually puncture them and introduce nutrients into the root directly.

When we go out into this big beautiful world, we find lots of microbes in the soil and lots of mycorrhizal fungi associated with roots. That's the natural way, so that's the way to make a high-Brix plant. We need to first get microbes into the soil and then feed them. A low-Brix plant won’t produce lot of sugar so the root exudates are minimal.

So if you practice soil health principles – reducing disturbance, reducing chemicals, keeping your soil covered, using microbial inoculants – you should see that play out in better plant health and higher Brix readings in your plants. Is that a fair conclusion?

Absolutely fair, and I’ve seen all of this play out. There aren't as many case studies as we'd like to see, but more farmers are getting into measuring Brix levels. As they adopt the soil health principles, they notice Brix levels are going up, and they don't have insects that I need to try to control reactively by spraying pesticides.

I haven't done this myself, but I've talked to scientists who will have two potted plants and they'll do something to stress out one of the plants, and they can watch the insects leave the other plant and go to the stressed plant. It happens within hours. I've also seen that insects will go after a certain part of the plant that is unhealthy. If you have a broken branch, you can have a thousand insects feeding on that branch and nothing on the rest of the tree.

Sometimes people get confused because they're measuring a tree and they get pretty good measurements but they’re still getting insects. That's because a healthy tree is going to have uniformly high Brix. It won’t differ by more than two Brix. If it's differing by more than two Brix, you've got a problem. You may have a plug disease such as citrus greening, or other problems that are preventing transport through the plant. In that case you’ll see insects attacking the parts of the plant that are unhealthy.

I remember when I was a kid people would say, “You’ve got a coddling moth inside the apple? Just a little extra protein. It's no big deal.” Now knowing what I know, I'm going to throw it away because if it's adequate for the coddling moth, it's not adequate for me. Since we're talking about apples, take a bite out of an apple. If it turns brown in less than a minute, there are not enough antioxidants in there. It's a low Brix apple and you probably need to throw it away. It's going to be soft and squishy. If you can cut an apple in half and leave it on your table for 30 minutes and it has minimal browning, that is going to be a high Brix apple.

Now we could measure those apples with a refractometer, but you can also use your senses. Your eyes, your ears and your taste buds will tell you what is a healthy crop and what is no. So why measure? Because I can have an apple coming in at 7.8, and someone else says, “I got a much better apple over here coming in at 19.2.”

Apples can reach 19 Brix. (The fruit that is. Usually the leaves are going to be a bit lower.) That shouldn't be hard to hit. I have tasted oranges coming in at 21 Brix. Most oranges and apples are not that high right now, but when they are, you can taste it. We are tuned to healthy fruits and healthy vegetables and we enjoy it. If our children don't like eating vegetables, that's in part because they're low Brix. That's part of the reason because they don't taste good.

If you pick a fruit with the intention to let it ripen in the grocery store, it tends to have less flavor than one that's been able to ripen. Is there is there a Brix correlation and kind of a biological process that that plays into that?

When things start to ripen, their biochemistry changes. For example, when you eat a potato, it doesn't taste that sweet. But if you let it sit in your mouth and let it savor, the starch is converted into simple sugars and the potato starts to taste sweeter. Well, that is a form of ripening. We could say it's ripening in your mouth as you're eating it, and the starch is being transported by the amylases into the sugars.

That happens with fruit ripening, and usually when it ripens on the vine, you get maximal ripeness. Once you take it off, it no longer gets any nutrition from the tree. Sometimes it continues to ripen, not as healthy as it would if it were still attached to the tree. The best apple I've ever tasted was one I picked off of a tree and ate immediately. Never been able to get anything like that in the store because generally that stuff is picked weeks before it ever reaches me. And therefore it is not continually being given the sugar, which makes an apple so incredibly tasty.

We also get concentrations of sugar. So for example, if you have a big orange tree, you usually can't get the ones at the top. They will start to dry out, but they're still healthy and they taste like candy because of the concentration of the sugars as the water is slowly removed from it. It starts to shrivel a little bit and it doesn't look as appetizing, it’s simply concentrated sugar. That’s why raisins taste so much better than grapes. An old ripened fig tastes so much better than a fig that you pull right off the tree.

Once the grape is around about 22 Brix to 24 Brix, it’s picked and layed out in the sun and then all that sugar concentrates. Because it's so healthy, it's not attacked by insects. If it's lower Brix, it's more likely to be attacked, especially in storage by the raisin moth. The same thing goes with figs. If they are picked at maximum Brix level and then you dry them out, you simply have a concentration of the sugar and it tastes sweeter than it normally would..

So this is a bit out of your wheelhouse as an entomologist, but do you observe the same sort of resistance building towards fungal and bacterial pathogens with a healthier plan with higher Brix ?

As you say, it's outside of my realm of expertise. I have bachelor's degree in entomology, master's degree in entomology, PhD in entomology. That said, the fungi I have found are not able to hold on to a plant at 10 Brix. I'm not a fungus expert, and I don't understand the biochemistry and the physiology associated with fungal pathogens, but in my observation I haven’t seen plants being infected when it's at 10 Brix. Another consultant told me he doesn't see anything at eight Brix and above. By the time you get to eight, nine or ten, you get near total fungal resistance. You may have a few insects that are attacking it, but the fungus is done. It just can't penetrate a plant leaf or the root.

That’s because at about 10 Brix the plant gets too hard. You have too much silicon, too much manganese, too much iron, too much copper, too much boron. These are too hard to eat and they form tough cross linkages and the plant can't be punctured by a piercing insect or the hyphae from a fungus.

It can still be eaten by a chewing insect, though. They're tough. They've got the mandibles. However, there is research on the beetles eating high Brix plants. The mandibles of a young beetle are tough, really awesome. After feeding on a plant that's really hard, the mandibles are completely sanded down. Some of those beetles were dying because they couldn't eat anymore. The minerals in the in the plants were too much and they starved to death.

Bacterial infections are different because they are usually transmitted by a sucking insect. These sucking insects tend to transmit certain bacterial pathogens. This is how we get citrus greening with the Asian citrus psyllid. The insect is making the selection, not the bacteria.

We have observed 9 Brix citrus trees with no Asian citrus psyllids on them whatsoever. However, if it had been attacked before and there actually is citrus greening inside the tree, the bacterial infection is probably still there and it will probably still be detectable, but the tree looks good. Nine Brix is not what I would call a healthy citrus tree, but it's healthy enough for many farmers.

Right now, if you tested the two of us, you’d have almost 100% chance of finding a rhinovirus inside both of us right now. That does not mean that we have the sniffles, but we're being exposed to rhinoviruses every day. There are over 100 different rhinoviruses out there, but they are not exhibiting any symptoms in you. That's what we see in the tree. Once it gets to nine Brix, the Asian citrus psyllid is not there. The bacteria may be transported around the tree, but it's not exhibiting any effect and the tree is just tolerating it. Can it completely clean it out? Theoretically it should be possible if the tree gets healthy enough, but I haven't done any testing in that regard.

I love how a plant's ability to resist pest and disease is so similar to ours. The anti-oxidants and other things that the plant produces to make itself healthy, it's trying to put them in the crop to make the crop healthy, and then we're trying to eat that to make us healthy. We're all trying to do the same thing. And once we understand that it can treat our soils accordingly, we should all get to the same place.

Exactly correct.

In one of your presentations, you were talking about weeds and how in certain cases, weeds can have a higher Brix than the plant surrounding them, so insects will be attracted to the crops you're growing rather than the weeds. As I understand it, weeds are plants that thrive in unhealthy soils. They're the first responders who come in and start making the soils healthy again. So is that why in the same soil the weeds are healthy, but the plants are not?

That is exactly it. We find weeds where the plants that you and I might want to consume won’t grow. Those weeds have been placed there by, you can it's God or say it's the wind, those seeds got there, but they're not going to grow until the conditions are just right. Then that weed will then grow and do the job that it's supposed to do. We find weeds in saline conditions, and their job is to take the salt down to manageable levels.

That said, weeds and crops are not in a clear-cut compartments. There are weeds that we can eat and get health out of, but we still consider them to be weeds. Then there are things like Brussels sprouts and the asparagus that some people like to eat and others don’t, but that doesn't make them weeds.

When we are looking at weeds growing next to a plant, we can compare Brix levels between them. If we are getting higher Brix on the weeds, then that means we are working very hard to raise weeds. We're not going to make money on that, but the weeds are doing a job trying to correct the soil. I've heard many farmers say, "I cannot get a handle on my weeds.” That's because you're raising weeds and you're doing a fantastic job of it.

People with healthier soils don't have a serious problem with weeds. And as the soil changes over time, you have certain weeds that appear in some parts of the property and other weeds that appear in other parts of the property. I know that the seeds for all these weeds are distributed all over my property, but they don't take hold unless there's a reason for them to take hold. This explains why some crops grow better in some environments than others do.