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Pest, Disease & Weed Timing CalendarsGreenhouse Pest Calendar
Greenhouse pests breed fast in warm, sheltered conditions, so the calendar that works is built on clean starts, steady monitoring and quick, informed responses.
Key points
- Use the empty period between crops for a full sanitation reset.
- Monitor weekly with sticky cards and direct scouting.
- Start with gentle controls and early biological releases.
- Follow greenhouse-specific label, re-entry and worker protection rules.
- Keep written counts and photos so decisions rest on trends, not hunches.
Why do greenhouses need their own pest calendar?
Warm temperatures, dense plantings and no winter break let insects such as aphids, whiteflies, thrips and fungus gnats reproduce quickly. A small number can become a large one in a few weeks. Outdoor timing rules do not apply, so your calendar should follow crop cycles, not seasons. Grouping benches or houses by crop and planting date helps you see which blocks are most at risk and which can wait.
Disease can move just as fast in humid air with poor circulation. Plan for both, using extension guidance written for protected crops.
Your calendar should list each crop cycle with sow, transplant, peak growth and clear-out dates, and mark when each pest has historically shown up.
What should happen between crops?
The gap between crops is the best chance for a clean reset. Remove old plants and debris, clean benches, floors and tools, and follow extension advice on disinfection. Check for weeds inside and around the house, since they shelter pests and viruses.
Let the house sit empty if your schedule allows, and repair screens, vents and doors. Inspect incoming plants from outside suppliers carefully, and keep new arrivals apart from the main crop for a few days.
Keep records of which supplier each batch came from. If pests keep appearing with one source, you will see the pattern and can raise it.
- Remove all plant debris
- Clean benches, floors and tools
- Control weeds inside and outside
- Quarantine new plants
How should you monitor through the crop cycle?
Hang yellow or blue sticky cards at the height recommended for your crop and check them weekly. Examine plants directly, especially leaf undersides and growing tips, and sample the same spots each time. Record counts by date. Number the cards and record the position of each, so you can compare like with like from week to week and spot hot spots early.
For example, if card counts rise for two or three weeks in a row, that trend matters more than a single high number. Use thresholds from extension for your crop when they exist.
Place cards near vents, doors and the most vulnerable crops, because those spots catch early arrivals.
When do you start control?
Start with the gentlest option that works at the current level, such as removing infested plants, adjusting environment, adding screens and using biological control agents. Beneficials work best when started early at low pest numbers, and your supplier or adviser can help with timing.
If you use any pesticide, follow the label for greenhouse use, re-entry intervals, ventilation and worker protection. Check compatibility with beneficials, and rotate modes of action to slow resistance.
Be patient with biological control. It usually works over weeks, so start it early rather than trying to rescue a house that is already overrun.
What does a weekly routine look like?
Set a fixed day for checking cards, scouting plants, adjusting ventilation and updating records. Walk the same route each time. Pay attention to doors, vents and any wet spots where gnats and disease develop.
Water carefully. Overwatering feeds fungus gnats and root diseases, and wet foliage supports leaf diseases. Space plants to allow airflow.
Keep floors and aisles free of standing water and weeds, which hide gnats and other pests.
How do you manage the end of the crop?
Before clearing, think about where pests will go. Heavily infested plants removed carelessly can shake pests into other houses or outdoors. Bag plants where they stand if you can, and dispose of them according to local rules.
Write a short season summary: which pests, when they began, what you did and how well it worked. It will guide the next cycle. A season summary shared with your adviser often reveals timing changes that can prevent next year's problems.
If you grow several crops in one house, plan clear-out dates so one crop's pests do not move to the next.
What records and compliance steps matter?
Record scouting counts, controls used, product names as on labels, dates, re-entry times and results. Many states have worker protection and licensing requirements that apply to greenhouse operations, so confirm them with your state department of agriculture.
Keep labels and safety information where workers can find them.
Check each pesticide label for greenhouse use specifically, since some products are not allowed in enclosed spaces.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.