Integrated pest management (IPM) means controlling pests in a fixed order of steps. You prevent pests first, then watch for them and remove them by hand. Next you release natural enemies, and you spray chemicals only as a last resort. A grow room that never needs a pesticide gets there because prevention, weekly checks and predators were planned and paid for before the first pest arrived. This part explains the five tiers, why spraying first fails, how to keep pests out, and how to find them early with sticky traps and a scouting log.
This article is compiled from several sources of equal weight. They are United States university extension services, a 2025 scientific study and European Medicines Agency guidance. Each source is introduced where it first appears and listed under References. Notes on Thai and Southeast Asian conditions are marked “Translator’s note”.
1. The five tiers of IPM, in order
IPM is not “organic sprays instead of synthetic sprays”. It is an order of decisions. You move down to the next tier only when the tier above it has failed.
| Tier | What you do | What happens if you skip it |
|---|---|---|
| 1. Prevention | Keep pests out, quarantine new plants, keep rooms clean, hold the right climate | You will need the lower tiers every crop, permanently |
| 2. Monitoring | Sticky traps, leaf checks, written records | Pests are first found in week 6 of flowering |
| 3. Cultural and physical control | Pruning, airflow, cutting out infested leaves | Small infested patches (hot spots) spread pests across the room again |
| 4. Biological control | Predatory mites and insects, nematodes, microbial products | Chemical sprays are the only option left |
| 5. Chemical control | Contact products, as a last resort | Resistant pests, residue on the buds, dead beneficial insects |
A few terms from the table:
- Beneficials are the predators and parasites that eat pests.
- Nematodes here are microscopic worms that kill insect larvae in the growing medium.
- Microbial products contain living fungi or bacteria that either infect pests or protect roots.
What to do: write the five tiers on a sheet at the grow room door. Before any spray, tick which tiers above it you have already tried. If tiers 1 to 4 are unticked, spraying is not yet the right step.
2. Why spraying first fails
2.1 Spider mites become resistant very quickly
The two-spotted spider mite (Tetranychus urticae) is the most common mite pest on cannabis. Its life cycle and control are covered in Spider Mites & Thrips. A 2025 study in the scientific journal Insects monitored resistance to acaricides (mite-killing pesticides) in field populations of this mite. It ranks this mite as the world’s second most resistant arthropod, after the diamondback moth (Plutella xylostella), a caterpillar pest of cabbage-family vegetables. (Arthropods are animals with jointed legs and a hard outer skin, such as insects and mites.)
Resistance in this mite has been documented to 96 insecticide and acaricide active ingredients, across 263 locations.
The study traces this to the mite’s biology. Each female lays over 100 eggs. One generation takes about 10 days at 25 °C. Its reproduction is arrhenotokous: unfertilised eggs hatch as males and fertilised eggs as females.
The mites resist pesticides in several ways. Some carry a changed version of the protein the pesticide is meant to attack (a target-site mutation), so the product no longer works on them. Others break the pesticide down with detoxifying enzymes, such as the cytochrome P450 family. Many eggs and short generations mean many generations per crop. Each spray leaves a few survivors, and those survivors breed the next, more resistant population.
Translator’s note: the 10-day figure applies at 25 °C. Many Thai grow rooms and greenhouses run at 30–35 °C. In laboratory studies, the mite developed from egg to adult in about 5 to 7 days at 30–35 °C. Shorter generations mean more generations per crop, so resistance builds faster.
What to do: list the active ingredient of every product ever used against mites on your site. Include products used by a previous operator if you know them. This list shows which products your mites may already survive.
2.2 Residue ends up on the buds you harvest
Pesticide residue builds up where the spray was heaviest and where the surface holds it best. On cannabis, that is the bud (inflorescence), which is covered in sticky resin glands (trichomes). For most active ingredients, nobody has studied well what they turn into when the flower is burned or heated (their pyrolysis products). That is why regulated markets test cannabis flower against stricter residue lists than food crops. For the testing side, see Pesticide Residues on Cannabis.
What to do: plan your pest control so that once buds form, the only work needed is scouting and removing infested parts by hand. Part 2 sets out a weekly schedule that does this.
2.3 Sprays kill the predators before the pests
Beneficials walk across sprayed leaves all the time. So they usually take a bigger dose than the pest does. The University of Connecticut (a United States university whose IPM programme publishes greenhouse guidance) gives one example. Direct sprays of insecticidal soap are very harmful to three predatory mites. They hurt both the nymphs (young stages) and the adults of Phytoseiulus persimilis, Neoseiulus cucumeris and Neoseiulus californicus. (Insecticidal soap is a spray of fatty acids that kills soft-bodied pests on contact.)
What to do: before you spray anything over released predators, even soap, ask the supplier of the predators whether that product is safe for that species. Write the answer in your log.
3. Tier 1: prevention and keeping pests out
3.1 Quarantine for incoming clones
Every clone (a cutting rooted from a mother plant) brought in from outside can carry eggs and young pests that you cannot see yet. A quarantine hold gives those hidden pests time to hatch and show up before the plant reaches your main room.
| Day | Step |
|---|---|
| 0 | Put the new plants in a physically separate room, never in the flowering room |
| 0 | Check both sides of the leaves under 30× magnification (a pocket loupe or a clip-on phone lens). Hang one yellow and one blue sticky card |
| 1–3 | Optional: release predatory mites on the new plants as prevention |
| 7 | Second leaf check and card count. This catches pests that hatched from eggs missed on day 0 |
| 14–21 | Third check. Move the plants into production only if they are clean |
The two-to-three-week hold is a rule of thumb, not a tested figure. It is chosen to cover more than one pest generation.
Translator’s note: buying clones from another farm is one of the most common ways Thai growers bring in problems. The risks are spider mites, thrips and Hop latent viroid (HLVd). HLVd is a tiny infectious agent that often shows no visible symptoms, so a leaf check will not find it. See Hop Latent Viroid. Finding it needs a laboratory test. Before sending samples, ask the laboratory whether it tests for HLVd. A clone can also turn out to be a different strain from the one named.
If you have no spare room, use a separate grow tent in another part of the building. Give it its own fan and visit it last each day. Keeping your own mother plants also means you bring in outside plants less often.
What to do: before buying clones, prepare the quarantine space, a 30× loupe and two cards. Mark the 7-day and 21-day checks on a calendar.
3.2 Keeping rooms clean
Pests travel on hands, clothes, shoes, used soil and plant waste. These habits cut those routes:
- Work in clean rooms before dirty ones each day. This way you do not carry pests from an infested room into a clean one.
- Keep separate footwear for the propagation room, where cuttings and seedlings root. Young plants are the easiest to infest.
- Never move plant material backwards, from flower to vegetative to propagation. Older rooms usually carry more pests.
- Bag infested leaves inside the room before you carry them out. Pests can then not drop off on the way.
- Use fresh, sealed growing medium. Reused medium and standing water are the usual source of fungus gnats. These small black flies lay eggs in wet medium, and their larvae live there.
- Screen air intakes with insect mesh. Keeping pests out (exclusion) is the only control that pests can never become resistant to.
Translator’s note: in the Thai rainy season, saucers, puddles and blocked drains around a greenhouse stay wet for weeks. Empty saucers after watering and clear standing water near the intakes. Very fine mesh stops smaller insects but also cuts airflow. Purdue University extension advises screen rated at 192 microns (132 mesh) across vents against western flower thrips. It notes that extra exhaust fans or a larger screened area can make up for the lost airflow. After fitting mesh, check that the room still holds its temperature in April, the hottest month.
What to do: write a one-page room rule sheet with the room order, footwear and the “no moving backwards” rule. Post it at every door.
4. Tier 2: monitoring
4.1 Sticky cards: yellow versus blue
Sticky cards (sticky traps) are coloured cards coated with glue. Flying insects are drawn to the colour and stick to it. Counting them each week shows where flying pests are and whether their numbers are rising, often before you see leaf damage.
| Colour | Catches best |
|---|---|
| Yellow | Western flower thrips, whiteflies, fungus gnats, shore flies (small dark flies that breed on algae in wet areas), leafminers (larvae that tunnel inside leaves), winged aphids |
| Blue | Thrips in particular, because blue attracts thrips more strongly than yellow. Also shore flies |
University of Connecticut greenhouse guidance gives the following setup:
- Use at least 3 to 4 cards per 1,000 square feet (about 93 m²). That is roughly one card for every 23–31 m².
- Hang extra cards near doors and vents, where pests enter.
- Hang cards 10–15 cm (4–6 inches) above the canopy and raise them as the plants grow.
- For fungus gnats, lay a card flat just above the medium. This catches more than hanging it upright.
- Change and count the cards every week.
Spider mites have no wings, so cards do not catch them. You still need to check the leaves.
How to count a card:
- Before hanging, write the date, room and position on the card or a tag.
- Count with a loupe, because thrips are tiny. Count each type separately: thrips, whiteflies, fungus gnats, other.
- Hang new cards in the same positions every week, so the numbers can be compared.
- Look for two signals. One is a rise compared with last week. The other is one card much higher than the rest, which marks a hot spot to inspect first.
Translator’s note: in open or semi-open Thai greenhouses, cards also catch many harmless insects and fill up with dust. Change them as soon as counting becomes hard. Ask at agricultural supply stores for both yellow and blue cards.
What to do: hang the cards this week and count on a fixed day. That count is your baseline for the crop.
4.2 Scouting records, which regulators also require
The European Medicines Agency (the European Union body that regulates medicines) publishes a guideline on Good Agricultural and Collection Practice (GACP) for herbal starting materials, meaning plants grown to make medicines. It requires:
- pest control measures to be documented;
- records showing which plant protection products (any product applied to protect the crop) were used;
- a stated interval between the last treatment and harvest (the pre-harvest interval);
- every batch to be traceable to its source.
The guideline also says pesticide use should be avoided as far as possible.
Translator’s note: in Thailand, cannabis flower is a controlled herb under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568. This notification was issued under the Thai Traditional Medicine Protection Act B.E. 2542 and has been in force since 26 June 2025 (see Cannabis as a Controlled Herb in Thailand). The Ministerial Regulation on Controlled Herbs (No. 2) B.E. 2569 came into force on 30 April 2026 and tightens licence criteria for cannabis flower (see Thailand’s Two Ministerial Regulations of B.E. 2569). Check your licence conditions for the records and tests they require. This is educational information, not legal advice.
Write one row per scouting round:
| Date, scout | Room, zone | Card counts by colour | Leaf findings | Action taken (species, rate) | Product applied (active ingredient, rate) |
|---|---|---|---|---|---|
| (example) 3 Nov, Somchai | Flower 1, zone B | Yellow 4 / Blue 7 | Thrips larvae on 2 of 10 leaves | Amblyseius swirskii, 100 per m² | None |
Log the counts even when they are zero. A run of zero rows makes the first rise easy to spot.
What to do: start the log this week. Keep it on paper at the door or in a shared spreadsheet. Fill it in on the same day as the card change.
5. Tier 3: cultural and physical control
Cultural control means changing how you grow so pests and diseases do worse. Physical control means removing them by hand. These steps cost little, leave no residue and work against every pest.
- Remove infested tissue. Cut off leaves with mites, thrips damage or mould and bag them inside the room. One hot spot left in place keeps sending pests across the room.
- Prune for airflow. Thin out crowded lower growth so air moves through the canopy and leaves dry faster.
- Treat the hot spot, not the room. Deal with the infested plants and their neighbours first, so the rest of the room is left untouched.
- Let airflow and humidity control mould. In a dense, still, damp canopy, buds stay wet. That favours Botrytis cinerea, the grey mould that rots buds from the inside (see Botrytis (Gray Mold)). Moving air and controlled humidity do more against it than any product.
Translator’s note: two Thai conditions work against this tier. In the rainy season, outside humidity is very high, so a closed room depends on its dehumidifier (see Dehumidifier and Air-Conditioner Sizing for a Thai Flowering Room). During a power cut, the air conditioner, dehumidifier and fans all stop. The room then gets hotter and more humid at the same time. That raises the risk of bud mould. It can also push the room above 30 °C, where some predatory mites stop working (see Part 2).
Three practical steps help:
- Hang a thermometer-hygrometer that records the minimum and maximum, so you can see what happened during an outage.
- Put at least one circulation fan on a battery backup (UPS, a battery unit that keeps equipment running for a short time).
- After any outage, check the densest buds for mould over the next few days.
What to do: once a week, in the lowest third of the canopy, remove one handful of crowded or damaged leaves from each plant. Note the removal in the log.
Summary: what to do this week
- Post the five tiers at the door and tick the tiers you have tried before any spray.
- Set up a quarantine space before the next clone arrives.
- Post the room rule sheet at each door.
- Hang yellow and blue cards and count them on a fixed day.
- Start the scouting log, with zero rows included.
- Add a min/max thermometer-hygrometer and put one fan on battery backup.
Questions and your own results are welcome as replies directly under this topic.
References
- Kewedar S. et al. (2025). Acaricide Resistance Monitoring and Structural Insights for Precision Tetranychus urticae Management. Insects 16(5): 440.
- University of Connecticut Integrated Pest Management greenhouse guidance (sticky cards, insecticidal soap, biology of Phytoseiulus persimilis).
- European Medicines Agency, guideline on Good Agricultural and Collection Practice for starting materials of herbal origin.
This article is part of the Asiannabis Community educational series on pest and disease management. The content is for education in jurisdictions where cannabis cultivation is legally permitted.
Continued in Part 2: Integrated Pest Management for Cannabis: Predatory Mites, Beneficial Insects, Microbials and Spray Rotation (Part 2 of 2)