Companion Planting Effects On Aphids In Kale

ISEF Category: Plant Sciences

Subcategory: Agriculture and Agronomy  ·  Difficulty: Advanced  ·  Setup: Home Setup  ·  Time: Full Year

The Hook

Aphids can explode on kale fast enough to ruin a bed before you notice. The layout of nearby plants can change where pests land, feed, and spread. That means your garden pattern might matter as much as the plants themselves. You can test that with photos, counts, and a detector model.

What Is It?

Companion planting means growing different plants near each other so one crop changes the pest, pollinator, or microclimate around another crop. Think of it like arranging furniture in a room. The furniture changes how people move, where they stop, and what they notice first. In this case, the “furniture” is your planting geometry, and the “movement” is aphid activity on kale.

Push-pull, intercrop strips, and polyculture mosaic are three ways to arrange plants. Push-pull uses a plant that helps repel or distract pests, plus another that attracts them away. Intercrop strips plant different crops in bands. A polyculture mosaic mixes species across the bed. You are testing whether one layout lowers aphid pressure more than the others, using daily smartphone images and a YOLO detector, which is a computer vision model that finds objects in pictures.

Why This Is a Good Topic

This makes a strong science fair topic because you can measure a real farming problem with a clear variable, the planting geometry. Aphid pressure is visible, countable, and tied to crop damage, so your results can matter outside the fair. You also get to practice experimental design, image collection, and data analysis without needing a lab microscope.

Research Questions

• How does planting geometry affect the daily number of aphids detected on kale leaves?
• What is the effect of push-pull planting on aphid counts compared with intercrop strips?
• Does a polyculture mosaic reduce aphid pressure more than a single-species kale bed?
• To what extent do aphid counts differ between inner leaves and outer leaves under each planting geometry?
• Which planting geometry slows the first appearance of aphids on kale the most?
• How does the percentage of aphid-infested leaves change across the three planting layouts?

Basic Materials

• Kale seedlings or transplants, enough for each planting layout.
• Companion plants for push-pull, intercrop strips, and mosaic layouts.
• Plant labels and a garden map.
• Smartphone with a camera.
• Tripod or phone stand for repeatable images.
• Measuring tape or ruler.
• Notebook or spreadsheet for field notes.
• White background card or reference card for photos.
• Basic garden tools, such as trowel, gloves, and watering can.
• Insect ID guide or extension photos for aphids.

Advanced Materials

• Smartphone or DSLR camera with manual exposure control.
• Tripod or fixed mount for daily imaging.
• Laptop with Python installed.
• Annotated image set for training or fine-tuning YOLO.
• Pretrained YOLO model for insect detection.
• ImageJ for image review and measurement.
• Spreadsheet software for experiment tracking.
• Optional macro lens for clearer leaf images.
• Weather sensor or nearby weather station data.
• GPS or bed layout sketch for spatial analysis.

Software & Tools

• Python: Runs image processing, counting scripts, and basic statistics for your photo data.
• ImageJ: Lets you inspect leaf images, compare regions, and verify detector outputs.
• Roboflow: Helps you organize, label, and manage training images if you build your own detection set.
• Google Sheets: Tracks daily aphid counts, bed layout, and weather notes in one place.
• QGIS: Maps bed position and helps you check whether location in the garden affects aphid spread.

Experiment Steps

1. Define the main response variable, such as aphids per leaf or aphids per image, so every layout gets measured the same way.
2. Choose one garden size and set up replicated beds or plots for each planting geometry.
3. Plan a fixed photo method so lighting, distance, and angle stay constant across days.
4. Build a labeling rule for what counts as an aphid, a leaf, and a positive detection before you start collecting data.
5. Decide how you will compare layouts statistically, including how you will handle repeated daily measurements.
6. Add a control for weather, plant size, or bed position so you can separate geometry effects from background noise.

Common Pitfalls

• Changing camera distance from day to day, which breaks image counts and confuses the detector.
• Mixing up aphids with whiteflies, leaf spots, or soil specks, which inflates false positives.
• Using different kale sizes across layouts, which makes pest pressure look like a layout effect when plant age is the real driver.
• Letting one bed sit in more shade or wind than the others, which changes aphid behavior and weakens your comparison.
• Training a YOLO model on too few images, which makes the detector miss small aphids or overcount leaf texture as insects.

What Makes This Competitive

A competitive version of this project does more than compare averages. It tests replicated layouts, keeps the imaging method tight, and checks whether the detector agrees with human counts. Strong projects also look at spatial patterns, like whether aphids cluster on edge plants or spread through the bed in different ways. If you add weather data, plant growth data, and a clear statistical plan, your project starts to look like real field research.

Project Variations

• Test the same three planting geometries on collard greens or mustard greens instead of kale.
• Compare manual aphid counts with YOLO-based counts to measure how well computer vision matches human scoring.
• Add weather variables, such as rainfall or heat, to see whether one planting geometry protects better under stress.

Learn More

• USDA National Agricultural Library: Search for extension guides on aphid management, companion planting, and brassica pests.
• PubMed: Search review articles on intercropping, pest suppression, and plant-insect interactions.
• NOAA Climate Data Online: Find local weather data to compare with aphid trends.
• NASA Earthdata: Explore free tools and data literacy resources for environmental pattern analysis.
• Phytobiomes Journal: Search for studies on plant community design, pest pressure, and crop health in mixed plantings.