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Bud rot is a name that strikes fear into anyone that grows cannabis. This mold can turn any beautiful bud into a nasty, soft-to-the-touch mess and render an entire cannabis crop worthless. Knowing what can cause bud rot to take hold in your cannabis crop can help save labor and materials in the long run. 


When people think about preventing bud rot, they often think about humidity and storage. However, bud rot can be caused by something as natural as morning dew. While we may be able to control such factors in an indoor grow, outdoor grow conditions are much more different. 


Understanding how bud rot impacts a cannabis crop is the first step toward preventing crop destruction. From there, proper measures can be taken to keep bud rot at bay or combat this specific kind of mold. 




What is Bud Rot?



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Bud rot is one of the most common forms of mold that can impact cannabis crops. This cannabis-damaging mold is more formally known as Botrytis. Both indoor and outdoor grow setups can experience bud rot if conditions are not properly maintained. According to Volume 77 of Pest Management Science, some of the most common conditions for bud rot to grow in are ambient humidity and moisture.


This form of mold can spread from plant to plant by spores. These spores can travel by wind, tools, host, or plant-to-plant contact. Utah State University’s Pest Extension explains, “Spores germinate and colonize the plant tissue, and these new infections produce thousands of additional spores which become airborne and continue the infection cycle.”



Bud rot infects more than 200 plant species. According to the third edition of The Fungi, bud rot causes an annual loss of anywhere from $10 Billion to $100 Billion worldwide. This loss not only impacts commercial cannabis crops, but also traditional crops such as soy, wheat, corn, and beans. 



What happens if a human consumes cannabis that contains bud rot? The results can be concerning. According to Microbiology International, bud rot may not be toxic, “but in rare cases, can cause a respiratory allergic reaction called hypersensitivity pneumonitis, or “wine grower’s lung,” in which lung sacs called alveoli become inflamed.” In some rare cases, symptoms can become fatal. However you look at it, consuming cannabis that contains bud rot is a health hazard. 




What Does Bud Rot Do to Cannabis?



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Bud rot can quite literally consume a cannabis bud, leaving nothing but a disgusting, soft mess. 


According to Volume 43 of the Canadian Journal of Plant Pathology, “Symptoms of bud rot on cannabis and hemp plants include decay of a portion or of the entire inflorescence, followed by characteristic sporulation of the pathogen.”


In layman’s terms, this means bud rot will feed off of the cannabis bud, growing and spreading to other plants in the process. In a way, this process is similar to that of the mold that grows on strawberries. Once one berry is infected with mold, then it will grow and spread to the strawberries around it. 


This crop destroying mold can appear white or gray at first, before consuming the host plant and turning darker in color. In cannabis, it can be found not only in the bud, but also in the stem of the plant. This becomes increasingly dangerous when it comes to the cloning process to produce vegetative plants or preserve strains.


Systemic bud rot is caused when a non-flowering mother plant is cloned. If bud rot is present in the stem of the mother plant, then it could be passed on to the clones. If uncaught before cloning, then the clones will have a high likelihood of showing bud rot during the middle to end stages of the flowering process. In some extreme cases, this scenario can result in total crop loss or complete loss of the strain. 




What Can You Do With Cannabis That Contains Bud Rot?


The answer to this question is dependent upon two others. How advanced is the bud rot in your crop? And what are the laws governing the medical or recreational cannabis program in your state? 


In some instances, some cannabis can be processed into concentrate. This is done by using methods such as hydrocarbon extraction, which uses butane. According to information from the National Center for Biotechnology Information, “Hydrocarbon extraction methods can be used to avoid unwanted water and pigments such as chlorophyll.” 


In other instances, more morose instances, the crop may have to be destroyed due to health concerns. Destruction will often include filing paperwork with your state’s cannabis regulatory board. For more information about how to properly destroy ruined cannabis plants, please contact the regulatory body that oversees your state’s cannabis program. 




What Role Does Morning Dew Play in Bud Rot?


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It is common knowledge that moisture on a fully flowering cannabis bud is not an ideal situation for any grower to find themselves in. If the cannabis is grown in an outdoor setup, then Mother Nature may give your crop an unwanted layer of morning moisture. 


According to the National Geographic, dew is caused by “temperatures drop and objects cool down. If the object becomes cool enough, the air around the object will also cool. Colder air is less able to hold water vapor than warm air. This forces water vapor in the air around cooling objects to condense.” This can often be seen on the grass on your front lawn during mornings in the spring or summer.


As the sun rises, it warms the dew and the cannabis plant covered in it, making an ideal environment for bud rot to take hold. From there, the bud rot can grow and develop, devouring your cannabis crop until it is a brown mushy texture. Once bud rot sets into your plant, it can be difficult to eradicate. In many instances, it is found too late. 


The best course of action is to use proper preventative methods when possible. This includes regular testing of your cannabis crop. Vegetative plants, mother plants, and flowering plants all should be tested on a regular schedule to help prevent the onset of bud rot. Only through practicing proper preventative measures can you stand the best chance of keeping bud rot out of your grow. 






Works Cited


Boddy, Lynne. “Botrytis Grey Mould.” Pathogens of Autotrophs, vol. The Fungi, no. Third Edition, 2016, N/A. Science Direct, https://www.sciencedirect.com/topics/neuroscience/botrytis-cinerea.


Bunce, Nellie. “dew.” National Geographic Society, 19 May 2022, https://education.nationalgeographic.org/resource/dew/. Accessed 28 March 2023.


Lazarjani, masoumeh P., et al. “Processing and extraction methods of medicinal cannabis: a narrative review.” NCBI, 19 July 2021, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8290527/. Accessed 30 March 2023.


Punja, Zamir K. “The bud rot pathogens infecting cannabis (Cannabis sativa L., marijuana) inflorescences: symptomology, species identification, pathogenicity and biological control.” Canadian Journal of Plant Pathology, vol. 43, no. 6, 2021, p. 1. Taylor & Francis Online, https://www.tandfonline.com/doi/full/10.1080/07060661.2021.1936650. Accessed 2023.


Punja, Zamir K. “Emerging diseases of Cannabis sativa and sustainable management.” Pest Management Science, vol. 77, no. 9, 2021, N/A. Wiley Online Library, https://onlinelibrary.wiley.com/doi/full/10.1002/ps.6307. Accessed 2023.


Tishler, Jordan, and Justin Sullivan. “What Happens When Medical Marijuana Gets Contaminated? What you need to know.” Microbiology International, 2018, https://800ezmicro.com/blog-articles/182-what-happens-when-medical-marijuana-gets-contaminated-what-you-need-to-know.html. Accessed 30 March 2023.


Utah State University, Utah Pest Extension. “Bud Rot | USU.” USU Extension, N/A, https://extension.usu.edu/pests/ipm/notes_ag/hemp-bud-rot. Accessed 29 March 2023.






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