Why Do Bugs Attack Certain Plants? (And What You Can Do About It)

Have you ever walked through your garden and noticed some plants look like they’ve been through a war zone, while others are standing strong and untouched? It can be super frustrating, especially when you’ve poured your heart into your garden. What gives?

Turns out, it’s not random. Dr. Thomas Dykstra, an entomologist who knows a ton about bugs and plants, says that insects are actually pretty picky eaters. They don’t just munch on any plant, they go after unhealthy ones. Yep, that’s right. If your plants are struggling, insects see them as an all-you-can-eat buffet. Let’s dig into why bugsattack certain plants and what you can do to keep those pests at bay.

Healthy Plants vs. Unhealthy Plants: What’s the Deal?

To understand why insects pick on certain plants, we’ve got to talk about plant health. Think of plants like people. When you’re healthy, your body fights off colds and the flu more easily. But if you’re stressed, not eating right, or just run down, you’re a lot more likely to get sick.

Plants are the same way. Healthy plants have strong defenses, kind of like an immune system. Unhealthy plants, though, are like open invitations to insects, saying, “Hey, I’m easy to eat, come and get me!”

What Does “Unhealthy” Even Mean for a Plant?

Unhealthy plants are typically dealing with stress. This could be from:

• Poor soil quality (like low nutrients or bad drainage).

• Lack of water or too much water (yes, overwatering is a thing).

• Not enough sunlight.

• Damage from over-fertilising or using chemicals.

But here’s the real kicker: plants that are struggling don’t have the energy to produce the compounds that naturally keep bugs away.

Brix Levels: The Secret to Plant Health

Now, let me geek out for a second. Have you heard of Brix levels? It’s a fancy term for how much sugar is in a plant’s sap. Higher Brix levels = healthier plants.

You can measure Brix levels with a refractometer (a tool that’s not as complicated as it sounds). The higher the reading, the better. Why? Plants with higher Brix levels have more sugars, minerals, and nutrients. Insects aren’t into those. They’re actually drawn to low-Brix plants because those plants are weaker and easier to digest.

Think of it this way: bugs are like lazy shoppers. They don’t want to spend extra energy chewing through a healthy, nutrient-dense plant when there’s a weak one right next door.

Why Do Bugs Attack Unhealthy Plants?

Insects are nature’s cleanup crew. They’re designed to take out the weaklings to make room for stronger plants. It’s not personal, it’s just how nature works. Dr. Dykstra calls them “garbage collectors.”

When a plant is unhealthy, its sap has fewer sugars and more free-form amino acids. Bugs can sense this imbalance. It’s like walking into a bakery and smelling fresh cookies, you know where the goodies are.

Why are Bugs Attacking Certain Plants?

Let’s say you’ve got two tomato plants side by side. One is in well-composted, nutrient-rich soil, getting just the right amount of water and sunlight. The other is in compacted soil, struggling with too much shade.

Which one do you think the aphids are going to attack? The second one, 99 times out of 100. It’s not a coincidence. The second plant’s low Brix levels are like a beacon for pests.

What You Can Do to Keep Your Plants Bug-Free

Now that you know insects attack weak plants, let’s talk about how to keep your garden healthy and pest-free.

1. Feed Your Soil

Healthy plants start with healthy soil. Add compost, organic matter, and mulch to give your soil the nutrients it needs. A soil test can tell you exactly what’s missing.

2. Water Smart

Too much water drowns roots, and too little stresses the plant. Aim for deep, consistent watering. A drip irrigation system is a lifesaver here.

3. No Chemicals or Fertilisers!

All chemicals and inorganic fertilisers kill something, even if that's not what they are directly designed to do. Keeping a balance is key, natural additives such as compost are naturally more balanced and broad. Focus on health and nutrition like a full roast dinner instead of a chemical wonder tonic.

4. Check Your Plants Regularly

Keep an eye on your garden. The sooner you spot a stressed plant or a pest problem, the easier it is to fix. Look for signs like yellowing leaves, stunted growth, or an unusually high number of bugs.

"The best fertiliser is the gardeners shadow"- Chinese Proverb.

How to Measure Brix Levels (And Why It’s Fun)

If you want to go the extra mile, grab a refractometer online (they’re pretty affordable). Take a drop of sap from a handful of leaves and place it on the lens. The refractometer will give you a Brix reading.

Roughly- a reading below 12? That plant might need some TLC. Above 12? The bugs will go easy on you.

Bugs aren’t out to get you, they’re just doing their job. When insects attack a plant, it’s a clear sign that something’s off with its health. By focusing on building strong, resilient plants, you’ll naturally reduce pest problems without needing to rely on harsh chemicals.

Healthy plants are happy plants, and happy plants mean a happier you (and fewer bugs!).

So, next time you see insects swarming a plant, don’t reach for the pesticide. Use the insects as a tool in your toolbox the translate your gardens health.

Happy gardening!