Cultivation processes often receive meticulous attention from those who work with hemp, from seed selection to care during flowering. However, once the harvest is over, there are still critical stages that can determine the final state of the flowers: drying and curing. Not only are these moments essential for preserving texture and aroma, but they also represent a time when they need to be taken care of from diseases and silent enemies, such as botrytis.
This fungus, also known as gray mold, can develop even after the cbd buds have been harvested and stored. The presence of internal humidity, combined with unsuitable environmental conditions, can trigger its appearance and ruin the entire crop. Understanding how to eliminate botrytis in dried buds requires a thorough understanding of its causes, its signs, and the strategies that allow it to be controlled before it compromises an entire harvest. Below, we’ll look at the aspects that growers take into account to prevent this common threat in their CBD flower crops.
What is botrytis and how does it affect dried buds?
Botrytis, commonly known as gray mold, is one of the most persistent silent enemies in the world of hemp cultivation. This pathogenic fungus has the ability to appear at different times of the process, from flowering to even after drying, when everything seems to be under control. In the case of already dried buds, their presence can be especially frustrating, as it affects flowers that had apparently passed all the critical stages of cultivation.
The development of gray mold on dried flowers not only has aesthetic implications, but also compromises their integrity. Grayish spots, loss of firmness, and a musty odor are some of the most obvious indicators. According to recent scientific observations, this fungus does not need much to activate: it is enough for certain internal conditions to be generated within the bud for it to find a favorable environment and begin its expansion (Buirs et al., 2025).
Characteristics of gray mold
Botrytis cinerea is an opportunistic fungus. This means that it can lie dormant for days or weeks, giving no sign of its presence, until it detects enough moisture and heat to start growing. In studies on greenhouse cultivation, it has been observed that the most critical days for its appearance are between the fifth and sixth week of flowering. During this period, the inside of the buds usually registers higher temperatures and humidity levels than the general environment, thus favoring their appearance.
Infected flowers lose their firmness, acquire a soft or brittle texture, and in some cases may show a thin, cottony layer of gray. This aspect is not only a visual issue: botrytis directly alters the structure of the flower, weakening its tissues and reducing its ability to preserve.
Conditions that favor their appearance
The appearance of botrytis does not occur randomly. There are a series of environmental and physical conditions that, when they coincide, create the perfect scenario for its development. The first key factor is residual moisture. Even if the drying appears complete on the surface, the inside of the flowers can still retain water, especially in particularly dense varieties. In fact, it has been recorded that the relative humidity inside the bud can be up to 15% higher than in the outdoor environment, and the internal temperature can increase 2.5°C above that of the greenhouse.
This hot, humid microclimate is not easy to spot with the naked eye, but it creates a stable environment for botrytis spores to activate. Poor ventilation also plays an important role in this process. In spaces where air does not circulate fluidly, pockets of moisture form that, when trapped between the buds, serve as a starting point for infection. These situations are usually exacerbated during the summer and early autumn months, when outdoor conditions tend to be milder and wetter.
That is why environmental control is essential during all moments of the process, even in the post-harvest stage. Small variations in humidity and temperature can trigger major problems if not identified in time.
Common mistakes that increase risk
The appearance of botrytis in dried buds is not always due to external causes. In many cases, certain errors during the handling and conservation of flowers can favor their appearance, even when the cultivation has been successful up to that point. This section discusses some of the practices that, although common, can generate conditions that activate the presence of the fungus.
Improper or accelerated drying
The drying process is a delicate stage that requires patience and control. When flowers are exposed to excessive heat or overly aggressive ventilation, the outer surface can dry out quickly, giving a false sense that the process is over. However, the inside of the bud can still retain moisture, and that internal difference becomes a risk factor. Over time, that trapped moisture can promote fungal formation, even weeks after drying.
In addition, hasty drying can damage the flower’s natural aromatic and volatile compounds, reducing its integrity both in terms of preservation and quality.
Failure to trim or cure
Manicuring, i.e. the removal of small leaves around the bud, also influences the development of botrytis. If it is done very superficially, plant remains may remain that store moisture. On the other hand, if it is done too aggressively, the flower is directly exposed, facilitating its dehydration and weakening its structure.
During curing, airtight storage without proper regular ventilation can cause moisture released by the bud to be trapped. This internal condensation generates the exact environment that botrytis needs to activate. That is why controlled aeration during the first few weeks is so important: it prevents unbalanced internal conditions from forming and protects the flower from possible infections.
How to detect botrytis in dried buds
One of the biggest difficulties associated with botrytis in dried flowers is that it is not always detected immediately. In the initial stages, the signs are discreet and can be mistaken for normal variations in appearance.
The change in texture is usually one of the first clues. A bud that becomes soft, crumbles easily, or shows particularly brittle areas may be developing botrytis inside. Added to this is the appearance of dark spots or dull areas, along with a loss of the natural brightness that characterizes healthy flowers. Over time, a grayish, cottony, and faint layer can be observed that advances from the interior to the surface.
Smell also plays a key role. Instead of the usual aroma, a damp, earthy or even slightly sour smell is detected, indicating alteration in the flower. These signs often become more apparent during healing, so frequent visual and olfactory checks allow you to act before the damage spreads.
What to do if botrytis appears: steps to remove it
When botrytis is detected in dry buds, it is essential to act quickly. Although it is a complex organism, it is possible to contain its advance if effective and coordinated measures are applied from the outset. This section includes some of the most recommended actions to slow down their development and protect the rest of the crop.
Immediate separation of the affected material
Once an infected bud has been identified, the first step is to carefully remove it from the rest of the batch. This should be done with clean, sanitized tools, as the spores can be easily moved by contact. The affected material should be discarded in a separate space and should not be left near other flowers, even if they appear healthy. Preventing cross-contamination is key to preventing the fungus from spreading through the environment.
Adjustments to the drying environment
Reviewing and improving environmental conditions is a complementary step that can make a difference. Constant ventilation, without excessive drafts, helps to maintain stable humidity levels. The use of dehumidifiers can be especially useful in areas with more humid climates or in seasons of high ambient pressure. It is recommended to keep the relative humidity below 55% and avoid temperature fluctuations. In extreme situations, some growers resort to solar drying, although this practice can alter the original characteristics of the flower.
Application of effective biological solutions
In contexts where botrytis recurrence or where additional intervention is required, biologics can be applied to reduce the incidence of the fungus. According to the study by Buirs et al. (2025), one of the most effective treatments is the use of Trichoderma harzianum, a beneficial fungus that competes directly with botrytis and manages to reduce its progression by up to 91%. Other compounds, such as tea tree oil extracts, showed variable efficacy depending on the stage and pressure of the disease. These solutions must be used preventively, and their effectiveness depends largely on the time of application.
How to prevent it from coming back
Removing botrytis does not guarantee that it will not return. Therefore, long-term prevention is an essential component of crop and post-harvest management. Implementing stable and consistent measures helps to significantly reduce the risk of the fungus reappearing in future harvests or during prolonged storage.
Environmental control and constant monitoring
One of the keys is to maintain environmental balance at all times. Controlling ventilation, using well-aerated substrates, and moderating irrigation are practices that favor a drier environment that is less prone to fungal growth. During flowering, using fans from the first weeks allows you to reduce the levels of moisture accumulated inside the buds. It has been observed that these measures could reduce botrytis cases by up to 81% (Buirs et al., 2025).
Frequent monitoring is also invaluable. Checking the humidity, adjusting the temperature and observing the condition of the flowers allows you to detect any changes before they become a problem. This constant vigilance represents a very effective preventive barrier when combined with general good management practices.
Choosing less dense and hardy varieties
Not all varieties of hemp behave the same against botrytis. Some genetics develop denser flowers, which makes it difficult for air to circulate inside. During the warmer months, between July and October, opting for varieties with more open structures helps prevent the formation of humid microclimates. In addition, applying biocontrollers such as Trichoderma between weeks 2 and 4 of flowering is used to reinforce protection before reaching the most critical period.
These decisions, when made in advance, allow for a safer growing season, decreasing the likelihood of botrytis reappearing.
Conclusion
Eliminating botrytis in dried buds is possible when you understand how it acts, what triggers it and what measures can slow down its development. Through a combination of corrective and preventive actions, the integrity of flowers can be protected and their natural characteristics preserved for longer. From timely detection to the right choice of varieties, every decision counts.
At Maionais, the selected CBD flowers go through rigorous drying, curing and humidity control processes that allow them to maintain their original structure, colour and texture. This attention to every detail offers a reliable alternative for those looking for well-cared, clean, and mold-free flowers, even after the drying process.
References
Cheung, N., Tian, L., Liu, X., & Li, X. (2020). The Destructive Fungal Pathogen Botrytis cinerea-Insights from Genes Studied with Mutant Analysis. Pathogens (Basel, Switzerland), 9(11), 923. https://doi.org/10.3390/pathogens9110923
Buirs, L., Lung, S., & Punja, Z. K. (2025). The epidemiology and management of Botrytis cinerea causing bud rot on greenhouse cultivated cannabis (Cannabis sativa L.). Canadian Journal of Plant Pathology, 1–21. https://doi.org/10.1080/07060661.2025.2478250
