Downy Mildew Grocery Store Hunt

The activity below was contributed by Dr. Kelsey Wood during our podcast interview.

Ever wonder why your lettuce looks wilted or discolored? It might be the work of a sneaky thief called downy mildew! This microbe weakens lettuce plants without directly killing them.

In the following microbiology activity, you and your kids (or students) will put on your detective hats and head to the grocery store to see if you can spot downy mildew in action.

Like any detective, you’ll need to do some background research to understand the culprit. So, read all about downy mildew, how it harms lettuce, and its impact on farmers in this blog post: Downy Mildew: A Plant Pathogen Targeting Your Lettuce.

Here’s an additional downy mildew resource if you’d like to dive even deeper.

Once you’ve become a downy mildew expert, come back here, and let’s embark on a detective mission to see if you can spot it at the grocery store!

Become a downy mildew detective!

Materials:

• Notebook and pencil
• Magnifying glass (optional)
• Camera (optional)

Instructions:

1. Mission briefing: downy mildew is a plant pathogen that attacks leafy green plants. Your mission, should you choose to accept it, is to find evidence of downy mildew at your local grocery store!
2. The investigation begins: Head to the organic produce section with your notebook and pencil, magnifying glass (optional), and camera (optional). Make sure to look in the organic section, as you’re more likely to find downy mildew there.
3. Targets identified: Keep an eye out for these downy mildew hotspots: lettuce, spinach, Swiss chard, herbs such as basil, and other leafy greens.
4. Spotting the culprit: Downy mildew can manifest in a few ways. Look for leaves with:
   • Fuzzy white or grayish patches on the leaves
   • Yellowish or discolored areas
   • Geometric shapes on leaves
   It can be difficult to distinguish whether you’ve spotted fungus or downy mildew. Just do your best and consider all suspects!
5. Document your findings: If you find a plant with suspicious symptoms, use your magnifying glass (optional) to get a closer look and jot down your observations in your notebook (does it appear downy, or is it more powdery? Powdery mildew is easily confused with downy mildew). Draw a picture or take a photo to document your detective work!
6. Verify your findings: Search for photos of downy mildew online and compare to see if your photos look similar.
7. Case closed (for now): Congratulations, downy mildew detective! You’ve completed your grocery store mission and gained a new appreciation for the microscopic world that thrives around us. Remember, even something as seemingly simple as a head of lettuce can harbor a fascinating hidden drama.

The next time you’re at the grocery store, take a closer look at your lettuce. You might just encounter a silent thief in disguise! But remember, with exciting ongoing research, we can look forward to a healthier future for our leafy greens.