Why Do Insects Eat Certain Plants but Not Others? with Dr. Tom Dykstra

The Whole Farm Podcast

When insects show up in the field, the default response is almost automatic:
What do I spray?

It’s how modern agriculture has been trained to think: identify the pest, apply the solution, move on. But what if that approach is solving the wrong problem?

In our latest episode of the Whole Farm Podcast, CHONEX’s Michael Pisciotta and agronomist Les Riley sat down with Dr. Tom Dykstra to explore a different perspective—one that challenges some of the most common assumptions about plant health and pest pressure.

The core idea is simple, but powerful:
Pests aren’t the problem. They’re the signal.

Brix Isn’t Just About Sugar. It’s About Plant Function.

Most growers have heard of Brix. It’s often talked about in terms of sugar content, especially in fruit quality. But that definition only scratches the surface.

As Dr. Dykstra explains:

“Brix is a measurement… of the bending of light.”

In practical terms, growers measure Brix using a refractometer by squeezing a few drops of plant sap and analyzing how light refracts through it. While that measurement correlates with sugar levels, that’s not the full story.

“From a practical standpoint… we often say we’re measuring sugar. But from the technical standpoint, we’re just measuring the bending of light.”

Why does that matter?

Because Brix is actually giving you a real-time snapshot of plant health and internal function. It’s fast, inexpensive, and can be done right in the field in under a minute.

Dr. Dykstra puts it plainly:

“As far as inexpensive tests… you can’t beat it. And as far as overall health, you can’t beat it. This tells you the overall health of the plant.”

The Real Reason Insects Attack Certain Plants

For years, a common belief has circulated: insects avoid high-Brix plants because of high sugar levels. However, Dr. Dykstra explains in this episode that’s not true.

In fact, insects are highly attracted to sugar sources like nectar, molasses, and even pure sugar. So if it’s not sugar, what’s driving pest pressure?

The answer lies in protein quality inside the plant.

Healthy plants produce complete proteins—fully formed amino acid chains that are properly structured and folded. And here’s the key:

“These complete proteins cannot be digested by insects.”

On the other hand, stressed or unhealthy plants produce incomplete or ‘broken’ proteins, and that’s exactly what insects are looking for.

“They need broken stuff… This is what their digestive systems are tuned to.”

In other words, insects aren’t randomly attacking your crop. They’re selecting plants based on what they can actually digest.

And Brix? It gives you a proxy for whether those proteins are complete or broken without the need for expensive lab testing.

Insects Are Indicators

This is where the conversation really shifts.

Instead of viewing insects purely as a threat, Dr. Dykstra reframes them as indicator species.

Every insect you see in the field is telling you something:

• • Whether the plant is healthy or stressed
  • The degree of that stress
  • What kind of imbalance is happening

“Anytime I see an insect attacking a plant, it indicates to me… the degree of unhealth of the plant.”

With enough observation, patterns begin to emerge. Different insects show up at different levels of plant health. It’s not random, and it’s not binary.

This turns the field into something more like a diagnostic system. Instead of reacting to symptoms, you can start to read the signals.

A Better Question: How Do I Make the Plant Healthier?

Traditionally, pest management has been reactive:

Identify the insect → choose the product → apply the treatment.

But this conversation points to a different approach, one that’s gaining traction among growers exploring regenerative practices:

Improve plant health first, and pest pressure follows.

As Les Riley framed it during the episode, the shift is from:

“What insecticide do we need to spray?” to “How do I get my plant healthier?”

Brix plays a critical role here because it gives you immediate feedback.

You don’t have to wait weeks for lab results. You can measure today, make a change, and measure again tomorrow.

“The measurement takes about a minute… and it doesn’t cost you anything.”

Even small improvements matter:

“If we… measure it again 24 hours later… if it goes up… that means the plant is doing better.”

This is what makes Brix so powerful. It turns plant health into something measurable, trackable, and actionable in real time.

From Inputs to Systems: A Bigger Shift in Agriculture

What this conversation really highlights is a broader shift happening across agriculture.

Instead of focusing only on inputs, fertilizers, pesticides, and products, there’s growing attention on the biological system itself.

• • Brix measures how well the system is functioning
  • Protein quality reflects the output of that system
  • Insects provide feedback on system performance

Put together, they form a loop of information that growers can use to make better decisions.

That kind of visibility changes how you farm.

Instead of reacting after problems show up, you can work toward outcomes like healthier plants, stronger systems, and less reliance on reactive inputs.

What This Means for Your Operation

If you’re a grower curious about soil and plant health practices, this doesn’t require a complete overhaul overnight.

It starts with a shift in perspective and a simple tool.

• • Use a refractometer to measure Brix in the field
  • Track plant health over time
  • Pay closer attention to insect pressure as a signal
  • Focus management decisions on improving plant function

The goal isn’t to ignore pests. It’s to understand why they’re there in the first place.

Listen to the Full Episode

This recap only scratches the surface of the conversation.

In Part 1 of this episode, Dr. Dykstra lays the scientific foundation behind Brix, plant health, and insect behavior. In Part 2, the discussion will move into practical, in-field strategies growers can use to improve outcomes.

If you’re looking for a different way to think about crop health and a more proactive way to manage your operation, you don’t want to miss this conversation.