Short answer. Integrated pest management is a written routine, not a product. Keep pests out with clean stock, a 14-21 day quarantine and a clean-room-first workflow. Find them early with weekly scouting of leaves, tips and sticky cards. Act on pre-set thresholds, matching the tactic to the pest's life stage and your room temperature: predators first, contact tools in veg only, and chemical classes rotated by mode of action. Write every count down. This article is the programme; each pest article gives the species detail.
Pesticide registrations on cannabis differ by country, state and province, and many products are not legal on cannabis at all. This article names classes, not products or rates. Always follow the label and local law.
What is IPM, and why does cannabis need it more than most crops?
IPM for cannabis is a system of prevention, monitoring, thresholds and layered control, with chemicals as the last layer. Cannabis needs it more than most crops because the harvested part is the flower, which is smoked or extracted, so residues matter more than in a crop that is peeled or cooked, and because few pesticides are registered on it [1].
Indoor cannabis also hands pests ideal conditions. Rooms run at 24-28 C (75-82 F) all year, with no winter to reset populations. The crop is propagated as clones, so pests travel with the plant material. Cranshaw and colleagues name the two-spotted spider mite a key pest wherever cannabis has an indoor or greenhouse phase, and note that problems often involve mother plants used for cloning [1].
Three facts drive the whole programme:
- Pests grow exponentially. At 25-30 C, spider mites and aphids can double in 2-4 days in lab life tables. A week of not looking can mean a four- to eightfold increase. See temperature, humidity and pest population growth.
- Options shrink in flower. Almost every contact tool is off the table once buds form. Problems must be solved in veg.
- Prevention is cheaper than cure. Most indoor infestations are introduced, not spontaneous.
How do pests get into an indoor grow?
Most pests enter an indoor cannabis grow on plants, with clones as the main route, followed by people, pets, air intakes and reused media. Cranshaw et al. describe mother plants used for cloning as a common focus of spider mite problems [1], and the same logic holds for broad mites, hemp russet mites and root aphids, which are hard or impossible to see on a cutting.
| Entry route | Typical pests | Prevention |
|---|---|---|
| Clones and rooted cuttings | Spider mites, broad and russet mites, root aphids, thrips pupae in plugs, mealybugs | Trusted source, quarantine 14-21 days, dip or inspect |
| Seeds | Almost none | Seeds are the cleanest start |
| People and clothing | Spider mites, thrips, aphids, whiteflies | Clean-room-first, clean clothes, no garden visits before the grow room |
| Pets | Spider mites, thrips | Keep pets out of grow spaces |
| Houseplants and outdoor plants | Spider mites, aphids, mealybugs, whiteflies | No houseplants in or next to the room |
| Air intakes, doors, vents | Thrips, aphids, whiteflies, moths, leafhoppers | Fine insect screening on intakes; sticky cards at doors [2] |
| Reused soil or media, bags of compost | Fungus gnats, root aphids, shore flies | New or pasteurised media; store bags closed |
| Wind and silk (outdoors, between rooms) | Spider mites, russet mites | Airflow from clean to dirty areas |
How long should new plants stay in quarantine?
New cannabis plants should stay in quarantine for at least 14 days, and 21 days when the source is unknown or the plants are heading for a mother room (Grower practice, derived from life tables). The logic is life-cycle timing: a spider mite egg laid the day before you collect a clone hatches in roughly 3-6 days at 20-25 C and becomes an egg-laying adult in about 10-17 days, so 14 days lets one hidden cohort show itself (see spider mites).
Quarantine only works if it is real:
- Separate space. A different room or tent, ideally with its own air, not a corner of the veg room.
- Separate tools and clothing. Or quarantine is visited last each day.
- Inspections on a schedule. Day 0, day 3-4, day 7, day 10, day 14 (and day 21). Leaf undersides at 10-20x; growing tips and petioles at 40-60x for broad and hemp russet mites on days 0, 7 and 14; roots of one sacrificial plug or the root ball edge for root aphids on day 14.
- Sticky cards. One yellow card in the quarantine space from day 0.
- Indicator leaves. Tape-sample a few upper leaves onto clear tape and examine under magnification for eriophyid mites.
| Source of plants | Minimum quarantine | Extra checks |
|---|---|---|
| Own seed | None needed for pests | Check medium for gnats |
| Own clones moved between rooms | 0-7 days | Tip check at 40-60x if the mother room had any history |
| Trusted clean-stock nursery with records | 14 days | 40-60x tip check days 0, 7, 14 |
| Friend, swap or unknown source | 21 days | All of the above, plus root check |
| Any plant with confirmed russet or broad mites | Destroy or full treatment cycle before release | Treat as zero tolerance |
Some growers dip incoming cuttings in a contact solution (soap, oil or other classes legal where they live) before quarantine. A dip reduces mobiles but rarely kills all eggs, so it shortens nothing: the quarantine clock still runs (Grower practice).
What does a clean-room-first workflow look like?
A clean-room-first workflow orders every visit from the cleanest area to the dirtiest: propagation and mothers first, then veg, then flower, then quarantine, then any room with a known problem. It is the cheapest prevention there is (Grower practice, standard in greenhouse IPM).
- Wash hands or change gloves between rooms.
- Wear clean clothes that have not been in a garden, a barn or another grow that day; a dedicated overshirt or lab coat per room is better.
- Keep pets out of grow spaces.
- Disinfect pruning tools between rooms and between suspect plants.
- Never carry an infested leaf through a clean room. Bag it where you cut it.
- Set airflow from clean areas toward dirty ones, not the reverse, because spider mites disperse on air (see aerial dispersal).
What should a scouting round include?
A cannabis scouting round includes four checks: sticky cards, leaf undersides, growing tips and the root zone, each done the same way every time and written down. Doing it the same way matters more than doing it perfectly, because the goal is a trend line.
| Check | Tool | What you are looking for | Pests found this way |
|---|---|---|---|
| Sticky cards (yellow, plus blue for thrips) | Eye, 10x lens | Flying adults per card per week | Thrips, whiteflies, fungus gnats, shore flies, winged aphids, leafhoppers, moths |
| Leaf undersides, lower and mid canopy | 10-20x lens | Mites, eggs, nymphs, cast skins, stippling | Spider mites, thrips larvae, whitefly nymphs, aphids |
| Growing tips, petioles, upper leaves | 40-60x loupe or microscope, or clear tape lift | Tiny wedge or translucent mites, eggs with dimples | Broad mites, hemp russet mites |
| Medium surface and root ball edge | Eye, potato slice, 10x | Larvae, white wax, algae | Fungus gnats, root aphids, shore flies, root mealybugs |
| Whole plant | Eye | Honeydew, webbing, twisted tips, wilting, frass | Aphids, mealybugs, spider mites, caterpillars |
UConn Extension notes that sticky cards catch only flying adults; spider mites, broad mites, mealybugs and wingless aphids will never appear on them, and immature thrips and whiteflies are not caught either [2]. Cards supplement plant inspection; they do not replace it.
How often should you scout, and how many plants?
Scout weekly as a minimum and twice weekly when the canopy runs above about 26 C (79 F) or when a pest is already present. At 27-30 C, spider mite, aphid and thrips doubling times are a few days in lab life tables, so a weekly check can miss a doubling or two. UConn Extension likewise recommends spot-checking cards twice a week as temperatures rise [2].
| Grow size | Plants to inspect each round | Cards |
|---|---|---|
| Home tent, 1-4 plants | Every plant: 5 leaves each (2 lower, 2 mid, 1 top) plus 2 tips | 1 yellow at canopy, 1 flat at medium surface |
| Home room, 5-20 plants | Every plant, 3 leaves each, plus 2 tips on a third of plants | 2-3 yellow, 1 blue |
| Small commercial room, 50-500 plants | At least 10% of plants, chosen on a walking pattern, plus every plant near doors, intakes and lamps | 3-4 per 1,000 sq ft (93 m2), plus doors and vents [2][3] |
| Mother room | Every mother, every week, including 40-60x tip checks | 1 per bench |
Rules for good scouting (Grower practice, in line with greenhouse extension guidance [2][3]):
- Walk the same route at the same day and time each week.
- Flag every positive plant with tape or a tag and re-check it at the next round.
- Pick up cards one or two days after a release of winged parasitoids, not the same evening, so you do not trap the beneficials [2].
- Place cards 10-15 cm (4-6 in) above the canopy and raise them as the plants grow [2]. For fungus gnats, lay a card horizontally just above the medium [2].
- Change cards weekly; they lose catch as dust builds up [2].
What action thresholds should a cannabis grower use?
No published action thresholds exist for indoor cannabis, so the thresholds below are grower-set starting points to be adjusted with your own records (Grower practice). They are deliberately low, because the harvested flower has almost no damage tolerance and options shrink in flower. See action threshold.
| Pest | Veg threshold (triggers action) | Flower threshold | Typical first action |
|---|---|---|---|
| Spider mites | Any colony (adults plus eggs) on one leaf | Any colony | Predator release on hot spot; remove leaf; climate check |
| Broad or hemp russet mites | Any confirmed mite | Any confirmed mite | Isolate; in mothers, destroy or full treatment cycle; zero tolerance |
| Thrips | Rising blue-card counts over 2 weeks, or larvae on 10% of sampled leaves | Any rising trend | Extra predatory mites; check medium for pupae |
| Fungus gnats | More than about 10 adults per card per week, or larvae in potato slices | Same | Dry top layer; soil-dwelling predators, nematodes or Bti class |
| Aphids | Any colony with nymphs | Any colony | Parasitoid matched to species; spot removal |
| Root aphids | Any confirmed | Any confirmed | Isolate; drench-class biologicals in veg; break cycle between runs |
| Whiteflies | Rising yellow-card counts, or nymphs on leaf undersides | Any rising trend | Parasitoids or predators by temperature |
| Caterpillars | Any larva, frass or bored stem; moths in the room | Same | Remove by hand; Bt class on young larvae in veg and early flower |
Threshold tightening by stage: whatever count triggers action in week 2 of veg should trigger it earlier as the flip approaches, because the last safe window for contact sprays is the end of veg.
How do you decide what to do once a pest is found?
The decision runs in five steps: confirm the pest, check the stage of the crop, check the room climate, choose the tactic that hits the life stages present, then schedule the follow-up from the pest's development time at your temperature.
1. Confirm ID
- Lens: 10-20x for spider mites, thrips, aphids, whiteflies; 40-60x for broad/russet mites.
- Not sure? Don't treat yet. Tape-lift and look again, or ask for ID.
2. What stage is the crop?
- Propagation / mothers / veg -> all IPM tools available (step 3)
- Flower weeks 1-3 -> biologicals, removal, climate; contact tools only where legal and non-residual
- Flower week 4 to harvest -> biologicals, removal, climate only; consider early harvest if severe
3. Is the room climate inside the predator's window?
- Yes -> release the matched predator/parasitoid at the hot spot plus preventive rate across the room
- No -> fix climate first (see "environment as a weapon" in the pest article), or choose a
predator that tolerates the room (e.g. N. californicus for warm, dry rooms)
4. Is the infestation above the threshold where predators alone can catch up?
- Predator:prey worse than about 1:20 for spider mites, or webbing present
-> knock down first in veg (water wash, contact class compatible with the predator),
then release predators after any residue period on the label
5. Schedule follow-up from development time at YOUR temperature
- Re-check in half the egg-to-adult time; re-apply contact tools before survivors lay
- Rotate mode-of-action group every pest generation
- Record everything
How do you time repeat treatments to the pest's life cycle?
Time repeat treatments so the second application lands after eggs that survived the first have hatched, and before the resulting juveniles mature and lay. Most soaps, oils and many other contact classes kill mobile stages but not eggs, so a single treatment always leaves a cohort behind (Established in greenhouse IPM).
The window comes from the life table at your temperature:
- Earliest useful repeat = egg development time (the eggs must have hatched).
- Latest safe repeat = egg development time + juvenile development time + pre-oviposition period of the first survivors, minus a margin.
For two-spotted spider mites, lab life tables put egg development at very roughly 3 days at 30 C and 6-7 days at 20 C, and egg-to-adult at roughly 6-8 days at 30 C and 14-17 days at 20 C (see the life-table section of spider mites for the cited values). That gives:
| Room temperature | Repeat window for mobile-only tools (spider mites) | Practical schedule |
|---|---|---|
| 20 C (68 F) | about day 7 to day 12 | Every 7 days, three applications |
| 25 C (77 F) | about day 4 to day 8 | Every 5 days, three applications |
| 30 C (86 F) | about day 3 to day 6 | Every 3-4 days, three to four applications |
These windows are estimates from lab data on non-cannabis hosts; confirm with your own scouting. Degree-day thinking makes the point general: heat, not the calendar, sets the pace [7].
How do you rotate pesticides to slow resistance?
Rotate by mode-of-action group, so no group is used on two successive generations of the same pest. That is the core IRAC recommendation, which also warns that metabolic resistance can cause cross-resistance between groups [6]. Rotate by group number on the label, not by product name, because different brands often share one group.
Spider mites and thrips need the strictest rotation. Both are haplodiploid: males develop from unfertilised eggs and carry one set of chromosomes, so resistance genes are exposed to selection in every male (see haplodiploidy). UC IPM notes that spider mites develop resistance quickly and that some sprays make outbreaks worse by killing their predators [4].
Practical rotation rules (Grower practice built on IRAC principles [6]):
- Count pest generations, not sprays. At 27 C a spider mite generation is about a week: three weekly sprays of one group expose three generations.
- Use non-chemical layers (predators, removal, climate) so that sprays are rare.
- Never use a group again in the same run if it failed; assume resistance.
- Record the group number of every application in the journal.
- Follow the label and local law; many groups are not legal on cannabis anywhere.
How do biological controls fit into the programme?
Biological controls are the backbone of cannabis IPM: predators and parasitoids keep working in flower, leave no residues and do not select pesticide resistance. They work best preventively, released before pests are seen or at the first colony, and only inside their temperature and humidity window.
| Pest | Main beneficials (class) | Climate notes |
|---|---|---|
| Spider mites | Phytoseiulus persimilis (specialist); Neoseiulus californicus, N. fallacis (generalists); predatory midges | Persimilis needs above about 60% RH and suffers above about 30 C; californicus tolerates warmer, drier rooms [5] |
| Broad mites | Amblyseius swirskii, Neoseiulus californicus, N. cucumeris | Swirskii prefers warm rooms |
| Hemp russet mites | Generalist phytoseiids (evidence limited) | See hemp russet mite |
| Thrips | N. cucumeris, A. swirskii, Orius; soil predators for pupae | Some Orius strains diapause under short days |
| Fungus gnats, shore flies | Stratiolaelaps scimitus, Dalotia coriaria, Steinernema feltiae, Bti class | Keep media moist enough for nematodes, not soggy |
| Aphids | Aphidius species matched to aphid, Aphelinus, aphid midge, lacewings | Aphid midge diapauses under short days without supplemental light |
| Whiteflies | Encarsia formosa, Eretmocerus eremicus, A. swirskii | Encarsia prefers moderate warmth; Eretmocerus handles heat |
| Caterpillars | Trichogramma (eggs), Bt class (young larvae) | Outdoors and greenhouses mainly |
Judge progress with a predator:prey ratio counted on marked leaves weekly. For spider mites, extension guides describe control when predators reach roughly one per 10-20 pest mites [5]. Check pesticide compatibility before any spray near a release; many contact classes and sulfur harm predatory mites.
How should the room climate support IPM?
Run the room climate so it slows the main pests and suits the beneficials, within the limits set by the crop stage. The crop wins every conflict: late-flower humidity stays at 40-50% RH regardless of what mites prefer, because bud rot costs more (see botrytis).
| Stage | Typical set-point | IPM angle |
|---|---|---|
| Propagation | 22-26 C, 70-85% RH | Good for most predators; watch fungus gnats and shore flies in wet plugs |
| Veg | 24-27 C, 60-70% RH | Avoid canopy above 28 C to slow spider mites; keeps persimilis viable |
| Early flower | 23-26 C, 50-60% RH | Last window for preventive releases of humidity-sensitive predators |
| Late flower | 20-24 C, 40-50% RH | Prioritise bud-rot prevention; use dryness-tolerant predators |
Hot spots matter more than averages. A canopy 3 C hotter than the room under a lamp is where spider mites start. Measure leaf temperature with an infrared thermometer and fix hot spots with airflow (see VPD).
How do you clean up between runs?
Between runs, empty the room completely, remove all plant debris and media, clean every surface and wait before restocking, so that no generation bridges two crops. Spider mites, root aphids and thrips pupae survive in debris, cracks, reused media and on mother plants kept in the same space.
- Remove all plants and media; bag them inside the room.
- Vacuum and wipe surfaces, ducting, fan guards and tent seams; clean or replace intake filters and screening.
- Wash or replace trays, pots and irrigation lines; root aphids and gnat larvae shelter in trays.
- Disinfect surfaces with a sanitiser suitable for the material (see sanitation and prevention); wear gloves and eye protection.
- Leave the room empty and dry for several days if you can (Grower practice); without food, mobile mites die within days to weeks depending on temperature.
- Restock only from quarantined or own clean stock.
Mother plants are the weak point. Never keep mothers in a room with a known infestation, and treat the mother room as the cleanest room in the building.
How should pest records tie into a GenetixBay grow journal?
Log every scouting round, count, release and treatment in the GenetixBay grow journal, against the batch and plant IDs, so that sources, trends and what worked can be traced across runs. A count without a date and a plant ID is a memory, not a record.
| Field | Example | Why |
|---|---|---|
| Date, room, stage, day of flower | 2026-11-04, Room B, flower day 12 | Ties pests to crop timing |
| Temperature, RH, leaf temperature or VPD | 26 C, 58% RH, leaf 24.5 C | Explains pest speed and predator success |
| Card counts by pest | Yellow 1: 4 gnats, 0 whitefly; Blue 1: 7 thrips | Trend lines |
| Leaf sample counts | 5 of 30 leaves with spider mites; 2 persimilis seen | Predator:prey ratio |
| Plants flagged | IDs or tag numbers | Spread pattern |
| Action | Released 1 predator class at hot spot; removed 6 leaves | What was done |
| Product class and IRAC group, if any | Contact soap class; group not applicable | Rotation record |
| Source of plants | Clone batch ID and origin | Traces introductions |
| Outcome 7 days later | 1 of 30 leaves; 6 predators seen | Did it work? |
Weekly pest-check results are already part of the recommended journal routine; see grow journal 101. Shared journals turn one grower's lesson into everyone's data: when several members report hemp russet mite on the same clone line, that is a provenance warning.
What are the common myths about IPM?
- "A weekly preventive spray is IPM." Myth. Calendar spraying without scouting selects resistance and kills beneficials [4][6].
- "Clones from a reputable source don't need quarantine." Myth. Clones are the main route for mites and root aphids into indoor rooms, and eriophyid and tarsonemid mites are invisible without 40-60x magnification [1].
- "Sticky cards will tell you if you have mites." Myth. Mites and wingless aphids do not fly and are never caught [2].
- "Predators are a cure-all." Myth. They fail outside their climate window or when released too late [5].
- "Bugs appear from the soil." Myth. Indoor pests are introduced. Fungus gnats arrive as adults or in bagged media; they do not form from wet soil.
- "Spraying in flower is fine if it's organic." Myth. Organic classes still leave residues and wet buds; the issue is residue and moisture, not origin.
Common mistakes
- No quarantine, or a quarantine corner sharing air with the main room.
- Scouting by feel instead of on a schedule with written counts.
- Waiting for webbing, honeydew or twisted tips: those are late signs.
- Repeating sprays on a fixed weekly calendar regardless of temperature.
- Rotating products that share a mode-of-action group.
- Releasing humidity-sensitive predators into a hot, dry room.
- Visiting the outdoor garden, then the mother room.
Evidence
- Clones and mother plants as a focus for spider mite problems in cannabis: Supported by a hemp pest review [1]; generalised to other mites and root aphids as Grower practice.
- Sticky card density, placement, change interval and what cards cannot catch: Established in greenhouse extension guidance [2][3].
- Mode-of-action rotation to slow resistance: Established [6]; rapid resistance in spider mites Established [4].
- Quarantine lengths and cannabis action thresholds: Grower practice, derived from life tables; no cannabis trials.
- Re-application windows: calculated from non-cannabis lab life tables [7][8]; Supported as method, approximate as numbers.
