Current Impacts of Outdoor Growth of Cannabis in Colorado Fact Sheet No. 0.308 Crop Series|Production authors * Bob Hammon, John Rizza, Doug Dean

Biological concerns that acreage increasing annually. Hops is Background informa- the plant species that faces the greatest tion, and definition of Cannabis supports a diverse fauna potential crossover threat from any of the of insects and other arthropods, both harm- Cannabis specialist insects. Conversely, hemp and cannabis ful and beneficial. There are also numerous Cannabis is the plant species that faces the pathogens that could impact plantings, • Amendment 64, section 16 (d) greatest crossover threat from any of the to the Colorado Constitution depending on many cultural and environ- hops specialist insects. defines Industrial hemp (a mental factors. The specific list of insects Two specialist insects are potential distinct variety of Cannabis and pathogens associated with cultiva- pests of outdoor grown Cannabis in Colo- tion of Cannabis at any given site is not rado. These are the hops aphid (Phorodon sativa L.) as a plant of the well known, due in part to the clandestine humuli) and hemp russet mite (Aculops genus Cannabis and any part nature of production in the past. One sci- macularis). There are probably other spe- of that plant, whether growing entific survey conducted on an established cialists that feed on Cannabis in Colorado, or not, containing a Delta-9 marijuana garden in Mississippi found more but their presence has not been reliably tetrahydrocannabinol (THC) than 300 species of insects associated with confirmed. Of these two species, the hops concentration of no more than the garden. A large proportion of these spe- aphid has been long established, with 0.3% on a dry weight basis. cies were predaceous on other arthropods collections recorded in the early part of Under Colorado State law any and not plant feeders. Of the insect species the 20th century (Palmer, 1952). The hemp collected that were using the plants as a Cannabis with a percentage russet mite is widely established in indoor of THC above 0.3% is food source, the majority (43 species) were Cannabis production across the state (Whit- considered marijuana (https:// sap feeders, 15 were leaf chewers, nine ney Cranshaw, personal communication) www.colorado.gov/pacific/ utilized pollen and one was a possible root and has the potential to move to outdoor feeder (Lago & Stanford, 1989). production. The hemp borer (Grapholita de- agplants/difference-between- Much of the current pest biology lineana) is frequently mentioned as a pest hemp-andmarijuana). and management information available of Cannabis production on internet sites. It • Other items that help from written and on-line sources was writ- is present in the US as far west as Minnesota differentiate between hemp (Miller, 1981), but its presence has never ten by individuals with no training in ento- and marijuana include mology or plant pathology. This has led to been confirmed in Colorado (Todd Gilligan, production differences a Cannabis pest management information personal communication). (growth form, plant base that is incomplete, unreliable, and/or Several generalist insects will feed simply incorrect. Many potential pests of on Cannabis when it is grown outdoors. height,cultivation methods, Cannabis are host specific, meaning they These generalists tend to be ubiquitous and planting density, proposed feed exclusively on Cannabis and botani- would be present on any crop grown on a end use, plant sex, etc.). cally related plants. site. These insects include several species of Lygus bugs, stink bugs, grasshoppers, Cannabis is placed in its own and thrips. Two spotted spider mite (Tet- botanical family, the Cannibaceae. The only ranychus urticae), is a common pest of Can- other member of this family that grows nabis grown in indoor situations, and it is in Colorado is hops, Humulus lupulus. ubiquitous throughout lower elevations in There are currently about 150 acres of Colorado. There is no reason not to expect hops planted in Colorado, with about 100 occasional problems with this spider mite in acres of that total on the west slope, with outdoor production situations. Outdoor grown Cannabis plants will at- ©Colorado State University tract many species of beneficial insects and Extension. 7/15. *Bob Hammon, Extension Agent – Agronomy, Entomology natural enemies. Many types of general- John Rizza, Small Acreage Management Specialist www.extension.colostate.edu Contributing Author ist predators can be expected to prey on Doug Dean, Tri-River Area Director aphids, spider mites, rust mites and others insects that are attracted to the crop. Lady versities that are looking at the growth bird beetles, minute pirate bugs, preda- potential related to hemp (variety trials Future research tory thrips, damsel bugs, and many other mainly). Some examples of medical re- priorities for outdoor types of predators will be attracted. These search follow: cannabis production are all very broadly distributed and would -University of California's Center for be found on most crops or other vegeta- Medicinal Cannabis Research (CMCR). tion grown on any plot of land. Focus is on scientific studies to assess The general conclusion that Reliable surveys of insects in the safety and efficacy of cannabis and can be reached from the currently outdoor grown Cannabis are almost non- cannabis compounds for treating medical available knowledge is that outdoor existent because of the past legal status, conditions. grown Cannabis poses no unique clandestine growing sites, and insect -University of Mississippi National Cen- threat to surrounding crops due to identification by individuals who are not ter for Natural Products Research. Studies emigration of insects, mites or plant trained inentomology. Hemp production Harmful and Beneficial Effects. pathogens. The actual amount of has been illegal nationally, and reliable -University of Washington Marijuana undesired biological migration from surveys in the crop do not exist. The pest Research Center, are studying a variety of a given Cannabis production field will fauna will surely differ from that found in aspects of marijuana, including preven- be more a product of farm and crop recreational/medicinal plants because of tion and treatment of abuse, its effect management than as a result of crop physical, biochemical and cultural differ- on the brain, and the epidemiology of species. ences in the plants and the way they are marijuana use and problems. Research that needs to be grown. One relatively disregarded issue conducted before the impacts of regards insect use of Cannabis pollen. Additional agricultural concerns outdoor grown Cannabis can be fully Cannabis is wind pollinated, but pollen associated with outdoor cannabis evaluated include: is a nutritious, protein rich food source production -Surveys of the insects associated for many insects and a variety of insects, Water use requirement information with small scale and large scale Can- including honey and other native bees is very difficult to ascertain on cannabis nabis and hemp production. utilize it as a resource (Stringer, 1992). production in an outdoor setting. How- This should include different ge- There is a lot of speculation on ever, a variety of sources were examined netic types and be done over as large internet sites regarding impacts of Can- and the following information presented of geographic range as possible and nabis pollen on honey bees and honey is the best pests that attack the crop. quality, but little science on bee usage known information available. -Plant pathogens associated with in field grown plants. Terrab et al. (2005) -Water use requirements Cannabis production, conducted found that Cannabis sativa pollen was o Hemp: 12-15 inches per year over a variety of environments and an important component of the floral o Marijuana: 25-35 inches per year production regimes. resources collected by honey bees in the o Traditional Crops: -Beneficial and other insects that Central Rif Region of northern Morocco. -Corn 20-25 inches per year utilize the plant environment, but do Paris et.al. 1975 did an analysis of two -Alfalfa 30-40 inches per year not attack the plant directly strains on Cannabis sativa pollen and -Tomato 15-25 inches per year -Pollen production from a range found that it was rich in cannabinoids -Peach 30-40 inches per year of Cannabis growing systems, and particularly active THC and THCA, the -Hops 20-30 inches per year including female only clones, female latter being able to be transformed into - Nutrient requirements (N, P, K) selected from seeded crops, seed physiologically active THC. Climactic fac- o Hemp: 120 lbs/ac N, 90 lbs/ac P, 140 production plants, and hemp pro- tors and particularly temperature played lbs/ac K duction blocks. an important role, since the THC content o Marijuana: Variable during different -Insects, bees, and other organ- at 24° degrees C/16hr was 30 times as growth stages, no reliable information isms that utilize Cannabis pollen. great as at 22 degrees C/16hr. available. -Differences in arthropod utiliza- Currently, Cannabis pollen has o Traditional Crops: tion of field grown hemp and out- been reported to be an allergen by the -Corn 100-150 lbs/ac N,40-80 lbs/ac P, door grown Cannabis for medicinal public, however, no research was found 40-120 lbs/ac K or recreational consumption. that supported or denied any claims of it -Alfalfa 20-30 lbs/ac N, 100-150 lbs/ac being more of an issue for some people P, 100-150 lbs/ac K than other plantpollens, in fact, the study -Tomato 90-130 lbs/ac N, 60-100 lbs/ac concluded that “As expected with most P, 140 to 215 lbs/ac K plant aeroallergens, Cannabis polleninha- -Peach 30-150 lbs/ac N, 30-80 lbs/ac P, lation has been noted to cause symptoms 50-150 lbs/ac K of allergic rhinitis, conjunctivitis, and -Hops 100-150 lbs/ac N, 40-60 lbs/ac P, asthma” (Ocampo and Rans, 2015). 80-150 lbs/ac K Colorado State University, U.S. Department of Additionally, there is no publi- Agriculture and Colorado counties cooperating. cized university research, at the time of CSU Extension programs are available to all without discrimination. No endorsement of products mentioned this report, on agricultural impacts on is intended nor is criticism implied of products not marijuana. Several states do have uni- mentioned. Chemical use for pests (pesticides, herbicides, etc.) is another area of limited information. Currently there are no pesti- cides registered by the U.S. Environmental Protection Agency (EPA), making any application of pesticides illegal. However, CDA currently has a “Marijuana Pesticides List” but they “do not recommend the use of any pesticide on marijuana, or any oth- er food crop for which the pesticide has not been specifically tested, registered and labeled to ensure its safe use with the respect to workers and consumers.” The current list was last updated in May and is found on the Colorado Department of Agriculture website. This site also has a list of selected examples of materials that cannot be used due to CDA criteria. However, none of the chemicals on the use list can legally be used under the EPA language. Another consideration that has im- pacted the public are related to nuisance odor complaints (currently focused on in- Literature cited door grow operation smells). At this time, Amaducci, Stefano, Alessandro Zatta, Marco Raffanini, and Gianpietro Venturi. 2008. the State of Colorado utilized local city Characterization of hemp (Cannabis sativa L.) roots under different growing condi- authority to deal with odor complaints. tions. Plant & Soil., Vol. 313 Issue 1/2, 227-235. The City of Denver has information on Arnold, Jessica. 2014. Energy Consumption and Environmental Impacts Associated their website, and suggests that there has with Cannabis Cultivation. Thesis at Humboldt State University. to be a finding that the odor is a public British Columbia Ministry of Agriculture and Food. 1999. Industrial Hemp Specialty nuisance in order for action to be taken. Crops Fact Sheet.Available Online: www.agf.gov.bc.ca/speccrop/publications/docu- There is no lawabout the amount of odor ments/hempinfo.pdf. that would constitute a violation, other Hall, Jack, Surya P. Bhattarai* and David J. Midmore. 2014. Effect of industrial hemp case law does exist in the state related (Cannabis sativa L) planting density on weed suppression, crop growth, physiological to smells from various instances, most of responses, and fiber yield in the subtropics. Renewable Bioresources. Vol 2. which have been dealt with mainly by the Johnson, Renee. 2015. Hemp as and Agricultural Commodity. Congressional Re- cleanup of the foul odor. search Service Report 5-5700. RL32725. Jorgensen, Uffe, and Kirsten Schelde. 2001. Energy crop water and nutrient use ef- ficiency. The International Energy Agency IEA Bioenergy Task 17, Short Rotation Crops. Lago, P.K. and D.F. Stanford. 1989. Phytophagous insects associated with cultivated marijuana, Cannabis sativa, in northern Mississippi. J. Entomol. Sci. 24(4) 437-445. McPartland, John M. 1997. Cannabis as repellent and pesticide. Journal of the Inter- national Hemp Association. 4(2): 87-92. Miller, W.E. 1981. Grapholita delineana (Walker), a Eurasian Hemp Moth Discovered in North America. Annals Ent. Soc. Am. 75(2) 184-186. Ocampo, Thad and Tonya Rans. 2015. Cannabis sativa: the unconventional “weed” allergen. Annals of Allergy, Asthma, and Immunology. 114 (3), 187-192. Palmer, M.A., 1952, Aphids of the Rocky Mountain Region. The Thomas Say Founda- tion, Volume V. A.B. Hirschfield Press, Denver Colo. 452p. Paris, M., F. Boucher, & L. Cosson. 1975. The constituents of Cannabis sativa pollen. Economic Botany 29: 245-253 Small, E. and D. Marcus. 2002. Hemp: A new crop with new uses for North America. In: J. Janick and A. Whipkey (eds.), Trends in new crops and new uses. ASHS Press, Alexandria, VA. 284–326. Stringer, B.A. 1992. Hemp. Gleanings in Bee Culture. 120(9) 502-503. Terrab, A., B. Valdes, and M. J. Díez. 2005. Study of the plants visited by honeybees (Apis mellifera L.) in the Central Rif Region (N. Morocco) using pollen analysis. Grana (44) 209-215.