Examples of natural pesticides: 3 effective investigation examples for science fairs

Starting with real examples of natural pesticides

Instead of starting with definitions, let’s jump straight into real-world materials you can test. Some of the best examples of natural pesticides come directly from plants that have evolved ways to defend themselves from insects and fungi.

Common examples of natural pesticides you can buy or make include:

• Neem oil (from the neem tree, Azadirachta indica)
• Garlic extract or garlic spray
• Chili pepper spray (capsaicin-based)
• Soap spray (insecticidal soap or mild dish soap solution)
• Diatomaceous earth (powder made from fossilized algae)
• Pyrethrum (from chrysanthemum flowers)
• Horticultural oils (plant-based or mineral oils)
• Bacillus thuringiensis (Bt), a naturally occurring soil bacterium

These examples include substances that are widely used in organic gardening and, in some cases, even in commercial agriculture. They’re perfect for controlled, data-rich science fair projects.

Example of project #1: Neem oil vs synthetic pesticide on aphids

This is one of the most straightforward examples of natural pesticides: 3 effective investigation examples you can run with basic supplies.

Core question

Does neem oil work as well as a common synthetic pesticide at controlling aphids on plants?

Background in plain language

Neem oil contains compounds like azadirachtin that interfere with insect feeding and growth. It’s widely used in organic farming and home gardening. The U.S. Environmental Protection Agency (EPA) classifies neem oil as a biopesticide and notes its low toxicity to humans and many beneficial insects when used correctly (EPA biopesticides overview).

This makes neem a strong candidate when you’re looking for real examples of natural pesticides that can be compared directly to store-bought synthetic sprays.

Basic experimental design

You might set up three groups of identical potted plants that are naturally infested with aphids (or you can introduce aphids from an infested plant):

• Group A: Sprayed with neem oil solution
• Group B: Sprayed with a common synthetic insecticide (follow label directions carefully and with adult supervision)
• Group C: Sprayed with plain water (control group)

Apply each treatment on the same schedule, at the same time of day, and from the same distance. Count the number of aphids on a set number of leaves per plant every 2–3 days for at least two weeks.

What to measure

You can track:

• Aphid counts over time in each group
• Plant health: leaf color, curling, wilting, presence of honeydew (sticky residue)
• Any signs of leaf burn or damage from the sprays

Plot your data as line graphs: days on the x-axis, average aphid count per plant on the y-axis. This kind of visual is catnip for science fair judges.

How to turn it into a strong investigation

This project becomes one of the best examples of natural pesticide research when you:

• Use at least 3–5 plants per group to reduce random variation
• Keep lighting, watering, soil type, and pot size consistent
• Document everything with a lab notebook: dates, times, concentrations, and observations

In your discussion, compare how fast aphid populations drop in the neem group versus the synthetic pesticide group. You can even reference extension resources like USDA National Institute of Food and Agriculture or your state’s cooperative extension pages for background on aphid control.

Example of project #2: Garlic and chili pepper spray on garden pests

If you want an experiment that feels a little more DIY, this is a classic example of natural pesticides you can literally cook up in your kitchen.

Core question

Which homemade natural spray—garlic, chili pepper, or a mix of both—does a better job of reducing insect feeding on leafy plants?

Why garlic and chili count as real examples of natural pesticides

Garlic contains sulfur compounds that repel many insects. Chili peppers contain capsaicin, which can deter feeding and sometimes kill soft-bodied insects. These are not just folk remedies; they’re widely discussed in integrated pest management (IPM) guides from universities, such as those from University of California Agriculture & Natural Resources.

These sprays are easy to prepare and give you multiple examples of natural pesticides: 3 effective investigation examples in one experiment:

• Garlic-only spray
• Chili-only spray
• Garlic + chili combined spray

Experimental setup

Use fast-growing, soft-leaf plants such as lettuce, basil, or bean plants. You’ll need enough plants to create four groups:

• Group A: Garlic spray
• Group B: Chili spray
• Group C: Garlic + chili mix
• Group D: Water-only control

Expose all plants to the same pest—often aphids, small caterpillars, or beetles you collect from a garden. If you can’t find enough insects outdoors, check local gardening forums or ask a school greenhouse manager; they often have more pests than they’d like.

Spray each group every few days, using the same volume per plant. Keep plants in the same location so they get equal light and temperature.

What you can measure

You can quantify:

• Number of insects per plant over time
• Percentage of leaf area eaten (estimate by comparing to a simple printed grid or by taking photos and visually scoring damage)
• Plant growth: height or number of leaves

This project is especially good for middle school students because the math is approachable but still meaningful.

Data analysis ideas

To make this stand out among other examples of natural pesticides projects:

• Calculate average insect counts and average damage per group
• Use bar graphs to compare final insect counts across treatments
• Note any phytotoxicity (plants getting damaged by your spray itself)

Then, in your conclusion, discuss whether the garlic + chili combination really outperforms the single-ingredient sprays or if it just smells worse. This is where you can talk about trade-offs: effectiveness vs. plant safety vs. practicality for gardeners.

Example of project #3: Diatomaceous earth vs soap spray on crawling insects

This third project rounds out our set of examples of natural pesticides: 3 effective investigation examples by focusing on a very different mode of action.

Core question

Is diatomaceous earth more effective than insecticidal soap at controlling crawling insects like ants, earwigs, or small beetles?

Why this is a strong example of a natural pesticide experiment

Diatomaceous earth (DE) is a fine powder made from fossilized diatoms (microscopic algae). It kills insects physically by damaging their waxy outer layer, causing them to lose water and dry out. Insecticidal soaps, on the other hand, disrupt insect cell membranes and are widely used in organic gardening.

Both are considered lower-toxicity options when used correctly and are often recommended by university extension services and IPM programs as safer alternatives to broad-spectrum synthetic insecticides. For background on safer pest control, you can look at resources from the National Pesticide Information Center, which is funded by the EPA and Oregon State University.

Experimental setup

You can test DE and soap spray using a simple arena setup:

• Use shallow plastic containers or trays as test arenas
• Place a piece of non-treated cardboard or a leaf in the center as a resting area
• Introduce a small, consistent number of insects to each arena (for example, 5–10 ants or beetles, collected from the same location)

Create three treatments plus a control:

• Arena A: Thin ring of diatomaceous earth around the center area
• Arena B: Cardboard or leaf sprayed lightly with insecticidal soap
• Arena C: Combination of DE barrier plus soap-treated surface
• Arena D: No treatment (control)

Observe insect survival and behavior over a set period, such as 24–48 hours, checking at regular intervals.

Measurements and observations

Because you’re working with live insects, be systematic:

• Record how many insects are alive at each time point
• Note whether insects avoid treated areas or cross them
• Observe any changes in movement speed or grooming behavior (some insects try to clean off DE or soap)

Graph survival curves for each treatment and compare the time it takes for 50% of the insects to die in each group.

Extending the investigation

This project can be scaled up for high school by adding variables:

• Different DE thicknesses
• Different soap concentrations
• Different insect species

These variations give you multiple examples of natural pesticides in action and let you talk about species-specific effects and environmental conditions.

More real examples of natural pesticides you can explore

If you want to go beyond these 3 effective investigation examples, there are several other natural options that can become the centerpiece of a strong project:

• Pyrethrum: Extracted from certain chrysanthemum flowers, pyrethrum is the natural source of pyrethrins used in many household sprays. It acts on insect nervous systems and works quickly, but can also affect beneficial insects and aquatic life.
• Horticultural oils: These oils coat insects and mites, interfering with respiration and egg development. They’re often used on fruit trees for scale insects and mites.
• Bacillus thuringiensis (Bt): A bacteria that produces proteins toxic to specific insect larvae (especially caterpillars and mosquito larvae) but not to humans when used properly. The CDC and EPA both discuss Bt as a relatively low-risk option when applied correctly (CDC mosquito control).

If you’re designing a project, you can use any of these as the core treatment and compare them to a control or to one another. That keeps your work grounded in real examples of natural pesticides being used in agriculture and public health today.

Turning examples of natural pesticides into a high-scoring science fair project

Lots of students spray plants and call it a day. The difference between a basic project and a standout one lies in design and analysis.

Here’s how to elevate your work:

Frame a clear, testable question

Instead of a vague “Are natural pesticides better?”, ask something like:

• “Does neem oil reduce aphid populations as effectively as a synthetic pesticide on bean plants over 14 days?”
• “Which natural spray—garlic, chili, or garlic + chili—leads to the lowest leaf damage from caterpillars on basil plants?”

These questions tie directly back to the examples of natural pesticides: 3 effective investigation examples described above and set you up for measurable outcomes.

Control your variables

Judges love when you show you understand variables. For each experiment:

• Independent variable: Type of pesticide (natural vs synthetic, or garlic vs chili vs water)
• Dependent variable: Insect count, leaf damage, plant growth, or insect survival time
• Controlled variables: Plant species, age, soil, pot size, water, light, temperature, amount and timing of spray

Collect data like a scientist

• Use consistent counting methods (same number of leaves or insects each time)
• Record data in tables, then convert to graphs
• Repeat the experiment if possible to show reproducibility

If you’re in high school, you can even run simple statistics (averages, standard deviation, or basic t-tests) to compare treatments.

Address safety and environmental impact

Even natural pesticides can be irritating or harmful if misused. Always:

• Wear gloves and eye protection when mixing sprays
• Work in a well-ventilated area
• Follow instructions on any commercial product labels

You can reference general pesticide safety guidelines from the EPA or educational materials from land-grant universities.

In your conclusion, discuss not only which treatment worked best, but also:

• Potential effects on beneficial insects like bees and ladybugs
• Possible impacts on soil and water
• Whether your natural options would be practical for real farmers or home gardeners

This level of thinking moves your project from “neat idea” to “serious environmental science.”

FAQ: examples of natural pesticides and science fair design

Q: What are some easy examples of natural pesticides I can test at home?
Garlic spray, chili pepper spray, neem oil, insecticidal soap, and diatomaceous earth are all accessible options. These examples of natural pesticides can usually be found at garden centers or made with grocery store ingredients, making them realistic for home or classroom experiments.

Q: Which example of a natural pesticide is safest to start with for younger students?
Insecticidal soap and diluted neem oil are often recommended for beginners because they’re widely used in home gardens and come with clear instructions. Always check labels and follow adult supervision guidelines, and avoid getting any spray in eyes or mouth.

Q: How many plants or insects do I need for my investigation?
Aim for at least 3–5 plants per treatment group or 5–10 insects per test arena. That gives you enough data to see patterns and strengthens your argument that your results aren’t just random.

Q: Can I mix different examples of natural pesticides together to make a super-spray?
You can test combinations (like garlic + chili), but do it carefully. Mixed sprays might stress or burn plants, and you’ll need a clear control group to know whether the mixture is truly better than each single ingredient.

Q: Where can I find reliable information about natural pesticide safety and effectiveness?
Look for .gov, .edu, or .org sources. Good starting points include the EPA’s biopesticide pages, the National Pesticide Information Center, and university extension sites from schools like UC Davis or Cornell. These sources explain how many of the best examples of natural pesticides are used in real agriculture and home gardening.