Monitor a crop by walking a fixed route on a fixed schedule, inspecting the same number of plants at each stop, writing down what you find and naming the cause before you decide to act. Counting the same way every time is what makes the numbers comparable from week to week and lets you see a pest population rising.
Monitoring (scouting) is the regular inspection of crops to find pests, diseases and natural enemies early and to measure their numbers.
Look The Same Way Every Time
The carrier asks for daily walks in the growing season. Daily is for the busy months; for a stable crop a visit once or twice a week is enough. What matters more is a method that does not change.
Step 1: Choose a route. Walk each bed along the same path, stopping at several places spread across the plot (the corners, the middle, and near edges and hedges where pests arrive first).
Step 2: Inspect a fixed number of plants at each stop. For example, 10 plants at each of 5 stops gives 50 plants (an illustrative scheme; scale it to the size of the crop). At each plant, turn over leaves, look at the growing tip and the stem base, and check fruit and soil.
Step 3: Record what you see. For each stop write the pest or damage, how many plants had it and how bad it was. The share of infested plants is simply infested ÷ inspected: 6 plants with aphids out of 50 inspected is 6 ÷ 50 = 12%.
Step 4: Compare with the last visit. A figure that doubles from one visit to the next tells you more than the figure alone.
Step 5: Decide with the threshold in hand (Action Thresholds).
Tools
- A hand lens or magnifying glass to see mites, aphids and eggs.
- A white tray or cloth: shake a branch or plant over it and count what falls.
- Yellow sticky boards at plant height. They show which flying pests are present and when they arrive, and are for monitoring; they also catch hoverflies and parasitic wasps, so use few (Physical Controls).
- A notebook, with a map of the beds.
Identify Before You Act
Match what you see to its cause. Damage patterns point to different culprits:
| What you see | Likely cause |
|---|---|
| Round holes in leaves, trails of slime | Slugs and snails |
| Seedlings cut off at the soil line | Cutworms |
| Tiny round “shot holes” in brassica seedlings | Flea beetles |
| Curled leaves, sticky honeydew, clusters of small insects | Aphids |
| Stippled, bronzed leaves with fine webbing | Mites |
| Chewed leaves with dark droppings | Caterpillars or beetles |
A poor match wastes effort. Remember that many insects on a plant are predators: ladybird larvae look like small spiny caterpillars and eat aphids; lacewing larvae resemble tiny alligators; hoverfly larvae are slug-like maggots among aphid colonies. Do not kill what you cannot name. Diseases are a separate case: for leaf spots, mildew and wilts see Plant Disease Management.
Keep A Crop Diary
A log of the date each pest first appeared lets the community predict the next year’s arrival and time its controls: row covers on before the moth flight, traps out before the beetles emerge. Over three or four seasons it is the most valuable pest record you will have.
Common Mistakes
- Looking only at the top of leaves. Eggs, aphids and mites are underneath.
- Counting differently each week. The change you see may be in your method.
- Treating the first sign. Compare with the threshold first.
- Misidentifying a predator as a pest. Name it or leave it.
What’s Next
- Learn next: Action Thresholds: When to Intervene — turning counts into decisions
- Combine with: Beneficial Insect Attractors — what to protect