Pests and Diseases of Cacti and Succulent plants
There are three main nightmares that these weird and wacky plants can succumb to and they are,
- Insect pests,
- Diseases such as fungal, viral and bacterial,
- Environmental such as in the growing conditions.
I won’t be listing all the different types of bugs etc or all of the fungal and bacterial diseases as there is plenty on these subjects already on the internet and it is a very large topic, I just want to include here what I do to prevent and treat these pests and diseases in general.
Thankfully Cacti and succulents are not as prone to as many pests as most other plants are because their thick skins and spines act as a deterrent for many bugs.
However if you have been growing cacti and succulents for any length of time you would need to be a very lucky person indeed to have never encountered any insect pests on your plants.
The most common being Mealy bugs and Spider mites which seem to be a magnet for certain types of cacti and succulents, followed closely by Aphids and scale insects.
Many different growers have their own ways of dealing with these pests but I am going to include what I do to most importantly to prevent these bugs as much as possible, as with everything in life prevention is always better than cure.
My Vegan dilemma
One of the biggest dilemmas I face when it comes to dealing with pests on my plants is that I am a Vegan, and for these of you who are not familiar with what a Vegan is, it is somebody who does not consume any animal products whatsoever, or wear any animal products including wool, leather, as well as avoiding any cosmetics and toiletries that have been tested on animals and Veganism is a way of living which seeks to exclude as far as it is possible and practicable all forms of exploitation of and cruelty to animals for food, clothing or any other purpose.
I have often said in my videos that I always like to live with nature rather than against it, and would often spend hours picking off slugs from the bottom of the pots of my plants and putting them back in the garden again a long distance away, I spray my cacti that are prone to Spider mites with rain water regularly which helps to prevent them as much as possible, I will use cinnamon oil on cotton wool balls all around my home and greenhouse to deter Ants without harming them and keeps other bugs away rather than harm them, and as for Spiders haha! I love them and just live with them they are part of our home and are the good guys when it comes to our plants, in saying that Sean runs a mile when he sees them :-).
Check out this video I have made for my You Tube channel called Desert Plants of Avalon on How to prevent Ants by using cinnamon oil:
Because of this I realize how important it is to prevent rather than treat, and thank goodness other than the odd mealy bug on my plants, I don’t often get many bugs on my plants these days, and although I do enjoying growing Carnivorous plants like Venus Fly traps and Sarracenias, Nepenthes etc, I can honesty say I never see them catch any insects indoors but I do feed them any dead insects such as flies, wasps, etc that I frequently see on my walks in nature or in my garden, and I know many growers will think I am nuts haha! but all my Carnivorous plants seem to be thriving and I have had my Nepenthes alata for over 20 years and is thriving 🙂
What I do to prevent Insect pests as much as possible
To prevent pests on my plants I water all of them in my collection 4 times a year with natural Neem oil.
The plants take up the neem oil systemically through their root systems which then gets stored inside their plant stems, this acts as a natural systemic insecticide internally and externally, this also helps to prevent many soil pests such as root mealy bugs and sciarid flies.
If I I do still find any pests on my plants, then I do the most humane thing I know of to get rid of them and that is by removing them with a cloth or cotton wool buds dipped in Isopropyl alcohol at 70% strength, on very spiny cacti such as Mammillaria I will spray the entire cactus/s with Isopropyl alcohol at 70% strength, and will soak cotton wool balls and a toothbrush in the Isopropyl alcohol to squeeze and gently brush the alcohol right into the spines to reach all the underneath of the spines that are very hard to reach, the spines on Mammillaria cacti can be extremely tight and very difficult to remove bugs from even with a toothpick due to their tight spines hiding the bugs you can’t see, worse still with the hooked spines, and soaking a cotton ball with Isopropyl alcohol and squeezing the alcohol right into them spines and rubbing the spines gently with a clean toothbrush dipped in the alcohol is often the best way of reaching the bugs you can’t reach, if this does not do the job then I will spray them with a Neem oil again on their foliage and I mix up the Neem oil with a natural soap such as Ecover, rather than resorting to dangerous chemical sprays.
When using Isopropyl alcohol on succulents especially Echeveria then I dilute it to 50% water and 50% Isopropyl alcohol to wipe off bugs. Please bear in mind that there are some Succulents such as Echeveria that may sadly lose their ‘hue’ on their leaves when being treated with either Neem and or Isopropyl alcohol as well as many everyday insecticidal sprays and systemics, but if the succulents lose their ‘hue’ due to being sprayed and treated is only aesthetic and does not harm the plant.
Neem oil is far more environmentally friendly and does not harm beneficial insects like Spiders and Ladybugs and Bees, as well as being safe for humans too. Many growers with large plant populations have great success with using biological methods of pest control such as introducing predatory insects that feed off the harmful insects, its what happens in nature naturally, but I have no experience of using this method myself, but something I would be very interested in trying in the future.
I would only ever use or recommend using chemical sprays ONLY if every other natural method has been used to control pests with no avail. I know that if I didn’t treat them they would quite easily wipe out my collection of 500+ plants if left untreated.
I recently had a bad attack of Mealy bugs on one of my Opuntia microdasys and I am pleased to say the mealies have all gone and I made a video for my You Tube channel called Desert Plants of Avalon and you can watch this video below and I explain a bit more about my dilemma in this video :
Here is a short video I made for my You Tube channel Desert Plants of Avalon when I was visiting a Botanic Garden where I noticed one of the worst cases of mealy bug infestation on this poor Agave:
Diseases and disorders
This is such a vast subject and there are many different diseases and disorders of cacti and succulents and much advice on the internet, so here I am going to start off for now by just covering the most common types of diseases or disorders that are commonly encountered in our collections, and will be extending more information on this as the weeks go on.
This is often happens because the soil in the pot that the plant is grown is has stayed damp for too long allowing fungi and bacteria to attack the root system, also if a plant has been recently repotted and it is watered too soon after repotting this can cause the plant to rot as the root have not had chance to heal from the re potting. One of the biggest causes of root rot is watering when the plants are dormant, Desert types of Cacti and many succulents like to be kept totally dry over their rest period from late October to early March and watering them during their dormancy is a sure way to encourage root rot. Bad drainage can also lead to root rot, succulent plants like to have a well drained potting mix. If you have a plant that is rotting at the base, it may be saved it you treat it as an emergency cutting by cutting away all traces of rot with a clean sterilized knife and letting the cutting fully callus over before potting back up again.
Check out this video below that I made for my You Tube channel Desert Plants of Avalon on Help my cactus is rotting what can I do?
Check out this video below I made on How to save a cactus from rot and take cuttings:
This often appears as brown corky scabbing on the epidermis of the plant, and is caused from too low of a temperature for the plant, black spots or scabs will often appear on cacti and succulents, and although they may not be life threatening they can be unsightly, plants kept for long periods in too low of a temperature are more likely to succumb to rots, so its important to move any plants showing signs of cold damage to a warmer spot.
Check out this video below that I made for my You Tube channel called Desert Plants of Avalon I have made on Cold damage on my Cactus:
Sun and heat damage
Sun and heat damage often happens when plants are growing behind glass and there is not sufficient ventilation, or plants have been exposed to bright sunshine after being for a period in a dull spot, moving plants outside for the Spring and Summer after overwintering then in a duller spot can often cause this to happen. Pale white sunken patches often appear on stems and the plants can sometimes look bleached where the chlorophyll has been damaged. Unfortunately the damage can’t be corrected but will grow out over time. If you have overwintered your plants in a shadier spot, then when it comes to moving plants back out into the garden in the Spring also acclimatize them slowly, to avoid scorch on the stems as much as possible
Etiolation is caused from lack of light which causes the stem to stretch out to try to receive as much light as possible making the plant look very strange and unnatural looking. you often see these strangely shaped and stretched out looking cacti on the bottom shelf at garden centres. There is no cure for this and the only remedy you can do is to cut off the spindly parts and move the plant into a sunnier position acclimatizing the plant slowly to its new bright spot. Over time it should send out new shoots from where it was cut and may end up looking very unique and different from its original pre etiolated appearance.
Chlorosis is a yellowing of the plant and is a condition where the plant is not able to make chlorophyll because it is lacking the nutrients in the soil to make it, and with cacti and succulents this is commonly caused by exhaustion of the soil nutrients, if a plant has been left for many years and is in desperate need of fresh soil, sometimes a re pot into fresh soil is all the plant needs to recover again, also the same pH of the soil over time can often become either too alkaline or too acidic and a change into fresh soil and switching from tap water to rain water is often all it needs, but sometimes it can commonly be caused by soil pests in the soil that are attacking the roots and stopping the plant from being able to absorb nutrients. Whenever a plant looks yellow and it is not caused from bright sunshine or lack of water, always take it out of its pot and inspect the roots, in the past I have always found that if I have a plant that is looking yellow and sickly, it is nearly always down to the plant needing fresh soil either caused by lack of nutrients or the pH of the soil becoming either too acidic or too alkaline over time, and or soil pests like root mealy bugs on the roots.
Check your plants regularly for signs of pests and diseases
As mentioned if at all possible, I will keep on top of keeping damaging insects at bay, the first thing I do on a regular basis is inspect my plants for signs of early infestation.
Although this is very time consuming considering I have 600+ plants, I do this in stages and it is a great way to get up close and personal with my lovely plants. but by doing this you will be able to see the first stage and signs of mealy bugs etc and at this stage I would normally use a cotton bud or a damp cloth dipped in either soapy water or Isopropyl alcohol to remove them.