I grow a lot of Trichocereus cacti from seed, I also send a lot out…
I know the title of this post sounds like a medieval book but I feel it is something we need to have a chat about! In many other aspects of our lives, hygiene has certainly evolved over human history and has resulted in the decreased incidence of certain illnesses and deaths from related diseases. From the simple act of hand-washing to prevent the spread of influenza and colds (edit: and now novel coronavirus which has brought this topic to the fore of society again), to the sterilisation of medical tools and surfaces to stop post surgical infections. It could also be argued that over-sterility/hygiene is now resulting in its own problems and chronic diseases due to a decrease in beneficial symbiotic organisms, both on our skin and within our bodies. What we need to achieve is a balance between the two, as humans are social creatures who now have the ability to spread disease far and wide, with the rapid ways in which we can travel and cross the paths of 100-1000’s of other humans each day.
In the same way that the role of hygiene has played in our lives, I believe hygiene processes can play a huge role in the incidence and reduction of disease within columnar cacti populations in cultivation. For example, I used to have small outbreaks of witches broom (a phytoplasma which causes mutated growth), but have virtually eliminated this through removal of the growth and sterilisation of knives and secateurs to stop the spread through dirty tools. So two simple hygiene factors; removal of infective material and sterilisation. How many people growing cacti do you know that have a great big old dirty knife they use to take cuttings and that they rarely or never clean?! Its like the reuse of syringes in early days that allowed the spread of diseases like HIV and Hepatitis B/C. Simple sterilisation of knives between cutting different cacti for propagation will stop/limit the spread of bacterial, fungal and viral diseases of cacti.
Some of the simple yet effective ways to increase health of your cuttings (Trichocereus, Cereus, Myrtillocactus are all columnar cacti) are listed below.
- When taking cuttings use a sharp serrated knife (serrations allow the knife to cut through hard woody cores easier than a plain knife)
- Remove damaged or diseased sections of cacti from your collection when you are propagating. You will never have a perfect collection though as some diseases are climate related, like the spotting that Trichocereus bridgesii gets in humid coastal weather in Australia. What you should be aiming for is good housekeeping.
- Use an agent to help seal cut ends, sulphur powder and charcoal are commonly used. Sulphur protects the cuts by providing an acidic environment unsuitable for germination of spores and establishment of bacteria and aiding in the drying of the cut.
- Consider using a preventative copper or phosphorus acid spray at the times of year when climatic conditions are most likely to encourage disease (we get them on the Sunshine Coast in autumn and spring when humidity and temperatures are ideal for fungal attack).
Reusing pots for plants has been mentioned as a possible transmission vector for disease, but I can’t say I’ve had issues and neither have several other serious cacti growers I have talked to. Diseases such as anthracnose are highly prevalent especially in the subtropics and I think you’e more likely to pick those up with water splash or airborne than through pots. It is always good practice to clean out used pots (I do this within a few hours as soil washes out easier before it fully dries) with a stiff spray nozzle on a hose. You could also use a 70% alcohol spray or bleach bath to give a final clean.
Hygiene, whilst super important, doesn’t stand alone however and other factors such as the health and nutrient status of the cactus and the microclimate it is growing in (humidity, daily temperature ranges, airflow, hours of sunlight etc) are all considerations for the keen cactus grower outside of their natural range.