How to Hunt Tomato Hornworms with UV Flashlights - No Plant No Life

Saturday, June 1, 2024

How to Hunt Tomato Hornworms with UV Flashlights

Tomato hornworms (Manduca quinquemaculata) are one of the most destructive pests that can afflict tomato plants. 

These large, green caterpillars can consume entire leaves, stems, and fruit, leaving plants bare and vulnerable to disease.

Traditional methods of detecting hornworms, such as visual inspection, can be time-consuming and often ineffective.

However, recent research has shown that using UV flashlights to hunt tomato hornworms is a highly effective method for detecting and eliminating these pests.

The Science Behind UV Detection

Tomato hornworms, like many other insects, have a unique physical property that makes them fluoresce under ultraviolet (UV) light. 

This means that when exposed to UV light, their bodies reflect the light and emit a bright glow. 

This phenomenon is due to the presence of certain molecules in the insect's cuticle, which absorb UV light and re-emit it at a different wavelength.

Benefits of Using UV Flashlights

Using UV flashlights to hunt tomato hornworms offers several advantages over traditional methods:

Increased accuracy: UV light makes hornworms easier to spot, reducing the risk of missing them during visual inspections.

Time-saving: With UV flashlights, you can quickly scan large areas of your garden, making the detection process much faster.

Reduced damage: Early detection means you can remove hornworms before they cause significant damage to your plants.

How to Hunt Tomato Hornworms with UV Flash Lights

Step 1: Prepare Your Gear

✅  A UV flashlight with a wavelength of 365-400 nm (nanometers)

✅ A pair of gloves 🧤

✅ A small container or bag to collect the hornworms

✅ A magnifying glass or handheld lens (optional)

Step 2: Inspect Your Plants

✅ Examine your tomato plants carefully, looking for signs of damage or hornworm droppings.

✅ Use your UV flashlight to scan the plants, paying attention to areas where the light reflects off the hornworms' bodies.

Step 3: Spot the Hornworms

✅ Under UV light, tomato hornworms will fluoresce, making them easier to spot.

✅ Look for bright green or yellowish glows on the leaves or stems.

✅ Use your magnifying glass or handheld lens to get a closer look, if needed.

Step 4: Collect and Remove

✅ Use your gloved hands to carefully pick up the hornworms and place them in the container or bag.

✅ Dispose of the hornworms humanely or destroy them.

Additional Tips and Tricks

1. Hunt at dawn or dusk: Hornworms are most active during these times, making them easier to spot.

2. Use a UV flashlight with a high intensity setting: This will help you detect hornworms more effectively.

3. Inspect the underside of leaves and stems: Hornworms often hide in these areas, making them harder to detect.

4. Consider enlisting a helper: Having someone assist you can make the process more efficient and enjoyable.

5. Keep your UV flashlight clean: Regularly clean your flashlight to ensure optimal performance.

Prevention and Control Methods

While using UV flashlights is an effective way to detect and eliminate hornworms, it's also essential to implement prevention and control methods to reduce the risk of infestation:

1. Use physical barriers: Cover your plants with fine-mesh row covers to prevent adult moths from laying eggs.

2. Plant companion plants: Certain plants, like basil and marigold, repel hornworms and other pests.

3. Apply insecticidal soap or neem oil: These organic pesticides can help control hornworm populations.


Hunting tomato hornworms with UV flashlights is a simple yet effective way to protect your tomato plants from these destructive pests. 

By following these steps and tips, you'll be able to detect and eliminate hornworms, ensuring a healthy and productive harvest.

Remember to combine UV detection with prevention and control methods for optimal results. 

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