Growing cacti without the use of heavy pesticides - a waste of time and money?

[Mrs.Green]

Mrs Green I think you misunderstood me. Ask away. That is how we all learn. I was just saying with your issues, sometimes its best to start again, and use what we learned from the experience to make sure it hopefully doe not happen again.

Thank you Mikethecactusguy.
I may have but I also should have used another heading! What I really was after is why cacti seems to be so pest and diseaseprone compared to many other plants we grow? Please remember that I have recently started with cacti again but I do have and have had a lot of other types of ‘houseplants’ for decades and as mentioned have had little trouble with pests and diseases. In spite of having a lot more plants than the average houseplant keeper.

When buying other houseplants I have inspected the plant thoroughly before and after buying it and if it seemed OK, I placed it with the other plants. I do know this seems silly but in all fairness it have worked well in 99 out of 100 cases I would say. I have a hard time beliving that I have been really lucky in spite of this, for so many years?

Doing something like that with cacti on the other hand, seems to be a sure receipe for disaster! In my opinion it shouldn’t be ‘necessary’ to go to such ‘extreme’ lengths when buying new plants, as I often sees described; taking the cactus out of the pot, washing it roots in hydrogen perioxide and keep it in quarantine for several months in another state preferably..

So back to the ‘why’ part. It would be interesting to know if growers that keep their outside ( in the ground, not a greenhouse) have as much issues with pests as those who keep their cacti in a greenhouse or strictly as houseplants?

How many of the most common pests have cacti in their natural habitat ever ‘met’ before they became garden/houseplants?

Is there a link between how long a certain genera/species have been grown in ‘captivity’ and how pest/disease prone they are?

People who live in areas were cacti grows naturally, have they as much problems with pests as others, and does in ground growing versus greenhouse have any impact on the occurance of pests?

[Mrs.Green]

I'm glad to come across this topic, since I had similar questions. I exclusively grow indoors (with the expection of some flowers on an outdoor windowsill). I have about 70 plants of which 30 are succulents. The only real issue I've had with succulents are mealybugs. They appear to always target the same species, Euphorbia and Opuntia. With Euphorbia I've seemed to prevent it by growing in an all mineral substrate. I've lost quite a large specimen of Opuntia Ficus Indica to the mealies and now the second year in a row they feast on a Opuntia Engelmanii. I must admit both Opuntias weren't getting the growing conditions they deserved. I'm giving the O. Engelmanii (after a thorough cleaning) to my father-in-law to be put in their garden. To come to the point, spraying insecticides in an apartment is very difficult to do in a safe way, especially in winter. I've been doubting a lot to give them a systemic insecticide (https://www.uhlig-kakteen.de/en/celaflo ... d=84502442). I add diatomaceous earth to my potting medium and (sometimes) to my water, but it's not clear whether it works or not. I try to be thorough in quarantining plants, providing clean pots and fresh soil. A few times a year I put out beneficial insects. That being said, I rarely lose succulents to bugs (I inspect a lot), improper watering is always cause n°1. It would nice to have one simple solution though.

Hi Ohugal ,

Nice to hear from a fellow indoor grower I have about 200 houseplants, the windowsills are pretty crowded The pest topic is interesting in my opinion too, for several different reasons. I am a firm beliver of that healthy and happy (as in perfect/very good growing conditions) plants are much less prone to getting pest/diseases. I suspect ( note; don’t know for certain) that growing desert cacti indoors in a very different climate is maybe part of the problem? My cacti will never get a fraction of the light/sunlight they would get in their natural habitat and I don’t think that part ( among others) really is helping on the ‘happy’ part. Even in summer there can be long periods of overcast weather here.

The epiphytic cacti seems to be doing better in our home, which doesn’t surprise me.

Interesting that you use predatory insects! I have been thinking about it but they are quite expencive here and will have to be shipped for a period of time before arriving. Can you tell me a bit more of which predators you are using and against what?

Ah, the watering yes..apart from the pests my biggest ‘problem’ too! How much is too little and how much is to much? Fearing root rot I suspect I have been to sparingly with the water for several of the cacti. A baby E. grusonii that I belived to be dead/dying , came back to life with a bit more water and the Selenicereus I have had for several years quickly came with new growth , who really grows fast, after starting a new watering regime.

[ohugal]

@ Mrs.Green, in relation to cacti and succulents I always have the feeling I cannot provide them with the right conditions to be 'happy'. It's also a question of experience. As the plants grow, you grow as well. Which is very satisfying.
We're moving to a new place with a garden and a (sort of) greenhouse. It will be a lot work, but I'm looking forward!
It appears you live in Norway, so I'm guessing the days are very short in winter. Do you have a place to hibernate you cacti and do you use artificial lighting?

I also have some Rhipsalis and a Disocactus. They thrive alongside my tropical plants. I pot them in the cactiguide epiphyt mix, which is 1 part soil, 1 part pumice, 1 part coir and 2 parts orchid bark.

Regarding the beneficial bugs, in Belgium we have Biobest, which is one of the market leaders in 'sustainable crop management'. I buy my bugs from www.biogroei.be, mainly because they grow endemic insects or at least insects which don't take over existing predators. For mealybugs I use Chrysopa, the larvae of some type of fly which eats a variety of pests. For fungus gnats I use the Hypoaspis Miles mite. I saw the same bug on a Dutch website and they claim it also works against root mealies. I'm not entirely convinced this is true, because the Hypoaspis Mile needs moist soil. I might give it a shot at one point though. I do have to say that even for indoor plants enviromental factors have an influence on the efficiency of the bugs. Timing is very important. I'm lucky Belgium is such a small country. Fast delivery is crucial.

I'm experimenting with some products of Rogis (www.rogis.nl). One is a garlic concentrate (Rogis OGF) you add to your water with each watering (against sucking insects). They also have a product called Root Protector based on azadirachtine against fungus gnats.

Ah yes... and yellow stickers, a lot of them.

[One Windowsill]

People who live in areas were cacti grows naturally, have they as much problems with pests as others, and does in ground growing versus greenhouse have any impact on the occurance of pests?

There are natural pests of cacti that have never adapted to the indoor environment, luckily. In some parts of South America you get a moth called Cactoblastis cactorum. You may have heard of it being introduced to Australia to control invasive opuntioids. https://en.wikipedia.org/wiki/Cactoblastis_cactorum

There are also plant parasites: https://en.wikipedia.org/wiki/Tristerix_aphyllus

Most growers of saguaro would pay good money to get a hole in the stem inhabited by a Glaucidium brasilianum http://wildsonora.com/species/glaucidiu ... m-cactorum

In Arizona they have the agave snout weevil, which explains itself. https://www.titantreeaz.com/blog/is-you ... t-weevil-1

[mikethecactusguy]

we all loose plants. We all do stupid things. Its part of the hobby. I had to trash this Melocactus today. Scale and root loss . A soggy mess. It was fine last month

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[Mrs.Green]

Post by ohugal » Tue Jun 22, 2021 9:59 pm
@ Mrs.Green, in relation to cacti and succulents I always have the feeling I cannot provide them with the right conditions to be 'happy'. It's also a question of experience. As the plants grow, you grow as well. Which is very satisfying.
We're moving to a new place with a garden and a (sort of) greenhouse. It will be a lot work, but I'm looking forward!
It appears you live in Norway, so I'm guessing the days are very short in winter. Do you have a place to hibernate you cacti and do you use artificial lighting?

Ohugal; I have exactly the same feeling too- hence the name of my blog; ‘growing cacti against the odds’ . Experience is gold!

A new place sound great and a greenhouse even better Yes, the days are very short in winter here. Hibernate..yes and no.. The rooms that the cacti are in aren’t heated, so the temperature in these rooms can get quite low in winter, especially on the windowsills. I did measure the temperature once last winter and it was 8 degrees celsius. ( this was measured in a cold period).

Artificial lightning..I will have to say yes and no to this question too..there is off course the ceiling lights but the light these provide, isn’t much to speak about, regarding plants.


Thank you for the info regarding predatory insects! I have been reading a bit about them and the use and as you say, both the environmental factors and time ( shipping) seems to be crucial , which has led me to question if it is worth trying. Fungus gnats have never been a problem here, the few times I have seen some( always after buying a new plant) they quickly disappear. The spiders which there are plenty of, may have something to do with that? So no need for yellow stickers here

There are natural pests of cacti that have never adapted to the indoor environment, luckily. In some parts of South America you get a moth called Cactoblastis cactorum. You may have heard of it being introduced to Australia to control invasive opuntioids. https://en.wikipedia.org/wiki/Cactoblastis_cactorum

There are also plant parasites: https://en.wikipedia.org/wiki/Tristerix_aphyllus

Most growers of saguaro would pay good money to get a hole in the stem inhabited by a Glaucidium brasilianum http://wildsonora.com/species/glaucidiu ... m-cactorum

In Arizona they have the agave snout weevil, which explains itself. https://www.titantreeaz.com/blog/is-you ... t-weevil-1

Thank you One Windowsill Very intetesting! Yes, I have in fact read about the moth you mentions here and I do wonder if its a wise idea to introduce ( another) foreign species to Australia ( or any place) ? History is full of examples of similar introductions who have gone very wrong.. or as the saying goes; ‘The way to hell is paved with good intentions’..

The cactus plant parasite Tristexa aphyllus was at least nice looking! I have never heard of that one before, will have to look for more info on that one.

Saguaro growers..hm..wouldn’t such growers have to get very old to have any hope of seeing the little owl in their Saguaros? At least if they don’t starts with rather big plants? From the pics I have seen the holes are rather high up on the Saguaros, which makes perfectly sence.

we all loose plants. We all do stupid things. Its part of the hobby. I had to trash this Melocactus today. Scale and root loss . A soggy mess. It was fine last month

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Ouch...even a keen rescuer like me wouldn’t have tried rescuing that one.. Sorry about your cactus though and thank you for sharing.

[One Windowsill]

Saguaro growers..hm..wouldn’t such growers have to get very old to have any hope of seeing the little owl in their Saguaros? At least if they don’t starts with rather big plants? From the pics I have seen the holes are rather high up on the Saguaros, which makes perfectly sence.

While they are growing you have time to train the woodpecker you need to peck the hole for the owl to live in.

[snyorega]

we all loose plants. We all do stupid things. Its part of the hobby. I had to trash this Melocactus today. Scale and root loss . A soggy mess. It was fine last month

Oh no, sorry for your loss! Do you know what you could have done differently?

[Mrs.Green]

Saguaro growers..hm..wouldn’t such growers have to get very old to have any hope of seeing the little owl in their Saguaros? At least if they don’t starts with rather big plants? From the pics I have seen the holes are rather high up on the Saguaros, which makes perfectly sence.

While they are growing you have time to train the woodpecker you need to peck the hole for the owl to live in.

Hmm..I still not sure about this.. I would belive the right species of woodpeckers wouldn’t need training. But anyway , unless you have big Saguaros already in your garden , both the grower and the woodpecker would have to get very old before any pecking of a hole in the right hight could be done