Short answer. Most leafhoppers on cannabis are harmless passers-by. The one that matters is the beet leafhopper (Circulifer tenellus, also Neoaliturus tenellus), which carries beet curly top virus: incurable, worst on young plants, and found in 81% of symptomatic Colorado hemp samples in 2019. The potato leafhopper (Empoasca fabae) causes hopperburn, usually minor. Protect transplants with barriers, kill the weed hosts, watch yellow sticky cards and pull infected plants. Sprays cannot outrun a virus that moves in hours.
Which leafhoppers are found on cannabis?
Leafhoppers on cannabis are small (about 3-4 mm), wedge-shaped, jumping sap-feeders of the family Cicadellidae. Over a dozen species have been found in Colorado hemp fields, most of them transients that do not breed in the crop [1]. Three are worth knowing.
| Species | Where | Harm to cannabis | Source |
|---|---|---|---|
| Beet leafhopper, Circulifer (Neoaliturus) tenellus | Arid western US: Colorado West Slope, Columbia Basin, southern Idaho, central Oregon, Utah, Arizona, New Mexico, California | Only known vector of beet curly top virus to hemp; feeding itself causes little injury | [1][2][3][4] |
| Potato leafhopper, Empoasca fabae | Midwest and East, migrating north each year; also Utah | Hopperburn: yellow, scorched leaf tips, curling; usually low threat | [16][17][18] |
| Ceratagallia uhleri | Colorado (most common hemp leafhopper there) | Breeds on hemp but causes no significant injury and transmits nothing known | [1][2] |
| Others: Empoasca spp., Ceratagallia spp., aster leafhopper Macrosteles quadrilineatus | Pacific Northwest hemp | Role unknown | [3] |
Glossary: leafhopper, plant virus.
How do I recognise beet curly top and hopperburn?
Beet curly top in cannabis shows as pale green to yellow foliage, upward curling and puckering of leaves, twisted new growth and stunting; mid-season infection shortens internodes into a witches' broom, and badly stunted plants may die late in the season [2][4]. Severity is greater the earlier the plant is infected [4].
Hemp shows some odd variants. Plants can be "bisymptomatic": a twisted, stunted main stem with normal-looking side branches, though virus is detectable in both [1]. Some plants appear to outgrow symptoms [1][4]. Symptoms vary with variety, growth stage, temperature and virus strain [4].
Hopperburn from potato leafhopper starts as yellowing at the tips of serrated leaves, then scorching, curling and twisting; plants may be stunted [17][18]. Under UConn's description, damage can progress from first symptoms to leaf death in four to five days [18]. Light white stippling is of little consequence [16].
Differential diagnosis: curly top mimics herbicide drift, nutrient problems and broad mite damage; confirm by PCR test [4][7]. Hopperburn resembles drought, senescence or spider mite damage, so look under the leaves for the insects [16]. See How to diagnose any problem.
Leafhopper life cycle in numbers
Both important leafhoppers pass egg (inserted into leaf or stem tissue), five nymphal instars and a winged adult [2][18]. Development thresholds are 14.4 °C for beet leafhopper and 11.4 °C for potato leafhopper in the UC IPM models [8][13].
| Parameter | Beet leafhopper (C. tenellus) | Potato leafhopper (E. fabae) | Source / conditions |
|---|---|---|---|
| Lower developmental threshold | 14.4 °C (58 °F) | 11.4 °C (52.5 °F); 8.4 °C immatures under fluctuating temps | [8] sugar beet; [13] alfalfa lab; [14] |
| Upper developmental threshold | 35.0 °C (95 °F) | 30.0 °C (86 °F) | [8][13] |
| Egg | 111.1 °C-DD | 7-14 days in summer | [8]; [18] |
| Nymphs (5 instars) | 250.0 °C-DD | no DD split verified | [8] |
| Egg to adult | 361.1 °C-DD (650 °F-DD) | 435 °C-DD lab; 459 field (783 / 826 °F-DD) | [8][13] |
| Pre-oviposition | 13.1 d at 20 °C; 8.2 at 25; 6.4 at 28; 5.0 at 32 | no value verified | [9] lab |
| Eggs per female | 105 at 20 °C; 99 at 25; 116 at 28; 197 at 32; 163 at 19-36 °C fluctuating; 300-400 under optimal conditions | no lifetime value verified | [9]; [3] |
| Eggs per female per day (derived) | ~2.2 at 25 °C; ~5.0 at 32 °C | no value verified | from [9]: eggs ÷ (longevity − pre-oviposition) |
| Female longevity | 58.1 d at 20 °C; 52.7 at 25; 41.9 at 28; 44.8 at 32; 96.3 fluctuating | no value verified | [9] |
| Oviposition threshold | no value verified | ~9.5 °C (laid at 10 °C, not 9 °C) | [15] |
| Generations per year | ~3 in Oregon and Washington | 4-5 in Utah; 2+ in Connecticut | [3]; [16][18] |
| Intrinsic rate of increase r_m | no published value found | measured by Hogg (1985), highest in the warmest regime; value not retrieved | [14] |
| Sex ratio | no published value found | no value verified |
Sources and conditions: beet leafhopper degree-days from Idaho lab and field work on sugar beet (Harries & Douglass 1948) [8]; fecundity and longevity from constant-temperature lab work (Meyerdirk & Moratorio 1987) [9]; potato leafhopper from Illinois work on alfalfa (Kouskolekas & Decker 1966) [13]. No leafhopper life table has been measured on cannabis.
How long does a generation take at each temperature?
| Constant temperature | Beet leafhopper egg (days) | Beet leafhopper nymphs (days) | Beet leafhopper egg to adult (days) | Potato leafhopper egg to adult (days) |
|---|---|---|---|---|
| 15 °C (59 °F) | ~185 | ~417 | not viable as a linear estimate (0.6 °C above threshold) | ~121 |
| 20 °C (68 °F) | 20 | 45 | 64 | 51 |
| 25 °C (77 °F) | 10.5 | 24 | 34 | 32 |
| 30 °C (86 °F) | 7.1 | 16 | 23 | 23 |
| 35 °C (95 °F) | 5.4 | 12 | 17.5 | above upper threshold |
Computed as degree-days ÷ (temperature − lower threshold) from [8] and [13]. Linear estimates are unreliable near the threshold.
For potato leafhopper under cool fluctuating regimes (8-19, 10-21 and 13-24 °C), eggs took about 35, 29 and 16 days and nymphs about 47, 39 and 23-25 days [15].
Why do temperature and humidity matter for leafhoppers?
Warmth drives beet leafhopper reproduction hard: pre-oviposition shortened from 13.1 days at 20 °C to 5.0 days at 32 °C, and eggs per female nearly doubled from 99 at 25 °C to 197 at 32 °C [9]. Generation time drops from about 64 days at 20 °C to 23 days at 30 °C [8]. Hot, dry western summers are its home climate.
Cool weather shuts beet leafhoppers down. Arizona extension notes they become less active when daily highs fall below about 60 °F (15.6 °C) and stay on their overwintering weed or crop hosts [11]. That is why disease pressure is a spring and early-summer problem in the west.
Winter moisture in the breeding grounds matters more than your field. Colorado's beet leafhoppers are largely spring migrants from New Mexico and possibly Arizona, where winter-annual mustards feed them; a wet winter there, as in 2019, means more migrants carrying virus [1].
Potato leafhopper damage is worse in warm conditions, and drought worsens the injury [18]. Hogg (1985) found intrinsic and finite rates of increase highest in the warmest regime (23-34 °C) on a per-day basis, while gross and net reproductive rates peaked in the coolest (13-24 °C) [14].
Humidity: no published humidity effect on either species was found. Leafhoppers are rarely an indoor problem, so indoor set-points (veg 24-28 °C / 60-70% RH, flower 22-26 °C / 45-55%) are not a control lever; screening and clean mothers are.
How fast can a beet leafhopper population grow?
No intrinsic rate of increase has been published for the beet leafhopper, so a true exponential projection cannot be computed. A per-generation ceiling can be, from the lab fecundity data [9] and the degree-day model [8].
Method: maximum multiplication per generation = eggs per female × fraction female × survival. Assume a 1:1 sex ratio (assumption; no published value found) and 100% survival (impossible in reality, so this is a ceiling).
| Temperature | Eggs per female [9] | Ceiling multiplication per generation | Generation length (egg to adult + pre-oviposition) | Ceiling r = ln(multiplication) ÷ generation |
|---|---|---|---|---|
| 20 °C | 105 | 52.5x | 64.5 + 13.1 ≈ 78 days | ~0.051/day (doubling ~13.6 days) |
| 25 °C | 98.9 | 49.5x | 34.1 + 8.2 ≈ 42 days | ~0.092/day (doubling ~7.5 days) |
| 28 °C | 115.7 | 57.9x | 26.6 + 6.4 ≈ 33 days | ~0.123/day (doubling ~5.6 days) |
| 32 °C | 196.9 | 98.5x | 20.5 + 5.0 ≈ 25.5 days | ~0.180/day (doubling ~3.9 days) |
Derived figures, not published r_m; the generation length ignores the spread of egg laying, so these ceilings run high.
The point for growers is not the local breeding rate. CSU observed only adults in hemp fields and doubts the species reproduces on the crop [1], though a CSU lab study found beet leafhoppers survived 7-day periods on hemp and laid eggs that developed [5]. Either way, your risk is set by how many virus-carrying migrants arrive from weeds and rangeland, not by how many breed in your rows.
How does beet curly top spread to cannabis?
Beet curly top reaches cannabis when a beet leafhopper that has fed on an infected plant feeds on hemp; the leafhopper is the only insect vector in North America [1][10]. The virus is persistent and circulative but does not multiply in the insect [10]. A leafhopper can acquire it within an hour of feeding and transmit after a latent period of about four hours [10].
Retention is long. EPPO cites up to 30 days [10]; Soto and Gilbertson tracked a related curtovirus in leafhoppers held on a non-host for up to 30 days [12]; Arizona extension says leafhoppers transmit for the rest of their lives [11]. The virus is not passed to offspring [11].
Weed reservoirs feed the cycle. In Colorado, prickly lettuce, dandelion and chicory most often tested positive among 41 weed species surveyed [5]. In the Pacific Northwest, kochia, Russian thistle and tumble mustard are key leafhopper hosts [3]; in Colorado, winter-annual mustards (flixweed, pepperweed) support overwintering and kochia is where summer leafhoppers are easiest to find [1].
Other routes: grafting and vegetative propagation, such as cuttings from an infected mother, transmit the virus; tools are not thought to; preliminary evidence suggests infected seed may [4]. Two strains, BCTV-Worland and BCTV-Colorado, have been found alone and mixed in Colorado hemp [6].
Scale: BCTV was detected in 81% of hemp leaf samples from 12 Colorado counties in 2019, and earlier at western sites than northern ones [5][6]. It was formally reported on Cannabis sativa in western Colorado in 2020 [7]. In the PNW it is common in the Columbia Basin, southern Idaho and central Oregon, and less so west of the Cascades [4].
Where do leafhoppers come from and how do they get in?
Beet leafhoppers fly into cannabis fields in early spring from overwintering sites on weeds [3], and in Colorado mostly arrive as long-distance migrants from the south [1]. Potato leafhoppers overwinter in the Gulf states and arrive in the north on warm winds, reaching Connecticut from June; non-reproductive adults are carried south again in autumn [18]. Utah State lists June through harvest as their season [16].
Both are flying, wind-borne adults, so distance from source habitat matters more than hygiene. Purdue advises avoiding sites next to alfalfa for potato leafhopper [17]. For beet leafhopper, weedy rangeland and field edges with kochia, Russian thistle or mustards are the sources [1][3].
Indoors, leafhoppers are rare. The realistic indoor risk is not the insect but the virus arriving in a cutting from an infected outdoor or greenhouse mother [4].
How do I scout for leafhoppers?
Scout outdoor hemp for leafhoppers with yellow sticky cards at the field edge, checked weekly and replaced as needed, plus a sweep net through the canopy [2][20]. Colorado State says sweep netting is the best way to detect beet leafhoppers in hemp [1].
Identification is the whole job. Beet leafhoppers are 3.3-3.6 mm (about 1/8 in), pale green in summer, wedge-shaped, with no head markings [2][3]. Many other leafhoppers land on the same cards, so a hand lens or microscope is needed [2][20]. Colorado's common Ceratagallia uhleri looks superficially similar but is harmless [1].
For beet leafhopper, scout the weeds as well as the crop: regular surveys of kochia patches in western Colorado show when migrations have arrived [1]. CSU suggests treating breeding areas in nearby weeds before leafhoppers move into hemp [2].
For potato leafhopper, inspect leaf undersides from June for pale, wingless nymphs that run sideways, and check scorched leaf margins and curled leaves [16][18]. Shaking plants or sweeping collects adults [18].
Action thresholds: none established for either species in hemp [2][17]. Utah State reports potato leafhopper has generally not damaged Utah hemp enough to warrant treatment [16]. For beet leafhopper, the "threshold" is effectively any viruliferous leafhopper on a young plant, which is why prevention is all that works (Grower practice).
Glossary: sticky trap, scouting.
How do I control leafhoppers on cannabis?
For beet leafhopper and curly top, control means keeping infected leafhoppers off young plants, because once a plant is infected it cannot be cured and insecticides cannot stop a transmission that takes a couple of hours [1][2]. CSU adds that beet leafhoppers are resistant to many pesticides used on sugar beet [2].
| Tactic | Target | Evidence |
|---|---|---|
| Physical barriers (row covers, insect netting) over seedlings and transplants | Keeps migrants off when plants are most susceptible | Recommended by CSU [2]; Grower practice for timing |
| Weed-host control (kochia, Russian thistle, mustards, prickly lettuce) | Removes breeding and virus reservoirs | "Likely the most important option" per PNW, though often impractical [3]; [5] |
| Reflective mulch | Deters leafhoppers from landing | "May reduce" spread [1][4] |
| Rogueing infected plants | Removes virus source | [4] |
| Trap crops (sugar beet at field edges) | Concentrates leafhoppers for targeted treatment | Suggested by CSU [2]; untested in hemp |
| Clean planting stock | Stops clone-borne virus | [4] |
Which insecticide classes are used on leafhoppers?
Insecticides used against sap-feeding hoppers in other crops come mainly from IRAC groups 4A (neonicotinoids), 4C (sulfoximines), 3A (pyrethroids and pyrethrins), 9B (pymetrozine) and 29 (flonicamid) [19]. Most are not registered on cannabis, residues fail cannabis testing, and none prevents virus transmission [1]. Follow the label and local law; no brands or rates are given here.
For potato leafhopper nymphs on leaf undersides, contact materials such as insecticidal soap and horticultural oil are grower practice in veg; we found no hemp efficacy data. Purdue notes chemical control used in other crops is not an option for hemp producers in Indiana [17]; Utah State says approved insecticides exist if populations and damage are high [16].
Rotate by mode of action if you do treat. Glossary: mode of action, contact vs systemic.
Which natural enemies attack leafhoppers?
Leafhoppers are attacked by generalist predators (green lacewings, spiders, assassin bugs, big-eyed bugs), egg parasitoid wasps of the families Mymaridae and Trichogrammatidae, and big-headed flies (Pipunculidae) [2][3]. Conservation (flowering borders, no broad-spectrum sprays) is the only practical biological tactic.
No commercial release programme or release rate has been established for leafhoppers on cannabis (no published value found). Predators eat leafhoppers but cannot stop a single viruliferous adult from infecting a plant within hours, so biological control does not manage curly top on its own.
Can I use the environment against leafhoppers?
Outdoors, timing and site are the environmental levers against beet leafhopper. Plant away from weedy rangeland and field edges with kochia, Russian thistle and mustards [1][3]. Keep transplants under cover through the spring migration, because young plants are most vulnerable and severity is greater with early infection [2][4].
Planting-date logic from other crops: in Arizona spinach and beets, delaying planting until leafhoppers become inactive (daily highs below about 60 °F / 15.6 °C) reduces curly top [11]. For a summer crop like cannabis the equivalent is protecting plants through the main spring flight, not avoiding it. Local timing varies; use your own sticky-card records (Grower practice).
For potato leafhopper, reduce plant stress, since drought worsens hopperburn [17][18], and avoid fields next to alfalfa [17].
Cultivar: there is currently no information on hemp varietal resistance to BCTV [4]. Purdue suspects cultivars bred for western states may be more stressed, and more damaged, in the Midwest [17].
Trade-off: row covers on transplants raise temperature and humidity underneath; vent or remove them once plants are established and the main flight has passed (Grower practice).
What should I not do about leafhoppers in flower?
Do not spray broad-spectrum insecticides on flowering cannabis to "stop curly top"; the virus is already in the plant, the spray cannot prevent new transmissions and residues fail testing [1].
Do not take clones from plants with curled, yellowed or twisted new growth; cuttings carry the virus [4].
Do not keep infected plants in the field to "see if they grow out of it"; they remain virus sources even when side branches look healthy [1][4].
Do not mistake hopperburn for nutrient burn and change feeding; look under the leaves first [16].
Do not count every leafhopper on a sticky card as beet leafhopper; most species in hemp are harmless [1].
What are the common myths about leafhoppers on cannabis?
- "Spraying leafhoppers prevents curly top." Myth. Transmission takes hours and migrants keep arriving [1][10].
- "Curly top only spreads by leafhoppers." Myth. Grafting and cuttings also transmit it; seed transmission is under investigation [4].
- "Hopperburn is nutrient burn." Myth. Same look, different cause; find the insects [16][17].
- "Beet leafhoppers breed in hemp fields." Contested. CSU field observations found adults only [1]; CSU lab work showed oviposition and development on hemp [5].
- "Every leafhopper on the card is a threat." Myth. Over a dozen species occur in Colorado hemp and only beet leafhopper transmits a known hemp pathogen [1].
Common mistakes
- Transplanting unprotected seedlings next to weedy rangeland during the spring flight.
- Spraying after curly top symptoms appear instead of rogueing.
- Treating sticky-card totals as beet leafhopper counts without identification.
- Cloning from outdoor mothers in curly top regions without testing.
- Blaming nutrients for hopperburn.
Evidence
- Beet leafhopper as sole vector of BCTV and its prevalence in Colorado hemp: Established [1][5][6][7][10].
- Transmission speed (1 h acquisition, 4 h latent) and retention: Established in other crops [10][11][12].
- Degree-day models and fecundity: Established on sugar beet and alfalfa; not measured on cannabis [8][9][13].
- Insecticides ineffective against BCTV in hemp: Supported by CSU expert assessment [1][2].
- Reflective mulch and row covers: Supported in principle; untested in hemp [1][2][4].
- Hopperburn on hemp: Established as a symptom; yield impact unknown [17].
- Whether beet leafhopper reproduces on hemp in the field: Contested [1][5].
Glossary terms used here
- Glossary: beet curly top virus, leafhopper, plant virus, degree-day, fecundity, parasitoid
