BCSS - Forum

For a few years my small cacti collection (low hundreds) was root mealybug (RMB) free till I made the bad mistake of failing to quarantine a plant I bought from a well known grower which was plainly RMB infested. I should have sent it back or not been lazy. Due to lack of vigilance on my part over the last couple of years what was a small problem has now become a big one and I have decided drastic steps are needed. Part of those steps is to start this blog to initially humiliate myself but ultimately to encourage me to get off my backside and do something I can be proud of and rehabilitate myself.

I do not want to use noxious chemicals if I can avoid it which means that what I have decided to do is to repot nearly every plant in my collection. This obviously creates logistical issues. I began on Sunday by unpotting a few plants and giving them a good hosing down to remove any obvious RMB. Having done a few I decided to keep going. Even plants which appeared to be clean I decided to unpot just in case I missed something. At the end of the day I was left with a huge pile of unpotted plants (and no daylight!) so I placed them in some large trays in shallow water to keep the roots moist and there they remain in the garage.

Here is the first dilemma. Is it safe to leave plants in shallow water for a few days? Alternatively is it a good idea to let the roots dry out? I have come to the conclusion that the latter is a bad thing and that the former is equally unwise so I am planning a happy medium of replacing the water with a layer of moist compost for the time being. As you will appreciate Japan v Belgium and England v Colombia are not good for immediate repotting.

Without wishing to go too far off topic, I have already noticed that immersing roots in water has caused some species to send out new roots, particularly some parodias, echinocerei and matucana whereas others show no signs of this. Presumably some species have roots which react in different ways to others but which and why I can only guess at.

Anyway my main question, on which I should welcome some guidance, is what additional precautions should I take before repotting to ensure that no residual RMB remains which has not been jetwashed off already? However hard one tries there is always the chance of a RMB remaining hidden in a crevice somewhere. The small number I have repotted so far I have dunked in meths for a few minutes and then rinsed off which is time consuming and some may say pointless??

So there I stand at present. Any tips on what else I should do before repotting would be most welcome. Bear in mind I need to get it done quickish so I don't want to be hanging around waiting for the postman to bring me some expensive potion coming all the way from Peru.

I will try to remember to get the camera out and take a few pictures to make things a bit more interesting next time.

Whenever I have had reason to hosepipe the compost off plant roots, be it for bug infestation or if the plant is making no progress, I always let the roots dry thoroughly before repotting. I cannot think of any occasion when this has not worked.

The worst situation is to damage damp or new roots because this would create pathways into the plant for viruses and rot.

If I were you I would have no hesitation in doing the above, ensuring that all the old compost is very thoroughly blasted off. Water the repotted plants after a week.

You will be very lucky to rid your plants of root mealies by this method; there are still likely to be eggs remaining which will start the infestation anew. By not wishing to use chemicals, you have created a lot of work for yourself. You can normally control this pest by giving a compost drench each summer with a neonicotinoid (something ending in prid). By drenching you do not have any problems of inhaling aerosol droplets from spraying. The main side effect of using this chemical class is on bees, which is why their use tends to be restricted commercially to glasshouse crops rather than fields of rape, etc.

Hi,

I concur with all advice given so far but would add that you need to clean the benching where the plants normally reside.

Suzanne

Yes, pots, plants and staging need to be washed thoroughly as you move sequentially through your collection. This is one problem that you can't do a half job on and using an insecticide will give confidence that your work has been a success.

Wash'em, dry'em, pot'em up. If you run out of time just leave them dry at the root covered in newspaper. Cut away damaged and infected roots.

If you don't want to use the poisons, you'll have to do a fairly spectacular job of cleaning everything. Especially the roots of the pants, of course. Then fingers crossed for the next couple of years while the one spot you missed develops back into a full-blown infestation.

Leaving succulents sitting in water is never a great idea. A few hours is usually OK, even good, but a few days is pushing your luck. Why do you want to keep them wet anyway? What succulents are you growing that you can't let the roots dry out?

Thanks for the comments. Here's the big tray:


An epithelantha showing new roots:


And a small tray:


Does anyone have any viewson the efficacy or otherwise of meths and if I were to use something else to treat the roots now , what should it be?

Meths is 100% effective in my experience (if used on a dry root ball), but you are going to need a lot to give all the plants a root bath in it.

Dip each plant roots and stem in a neonicotinoid insecticide , allow to dry, pot up. The likelihood is that will sort the problem. I had a similar failure of quarantine a few years ago having been RMB free for 20 years. I just root washed and dipped the obviously affected plants though, and drenched the rest. Not seen a RMB since (10 years). These days every new plant gets a dip just to be on the safe side.


Sent from my iPhone using Tapatalk

First of all, good luck, and you are far from alone in struggling to control pests!

Here's a summary of my observations and suggestions.

There are two basic approaches:
1. Remove ALL of the pest, or
2. Kill ALL of the pest 'in situ, and
3. Whatever the approach, minimise any chance of them being reintroduced, or spreading if reintroduced.

In practice I think most of us try a combination of the three. And the reason 'ALL' is in capitals is there's little point going to the effort if one or more small populations remain to spread back through the plants.

Removing? Washing off roots is an excellent idea if you have the time. Yes, then let them dry. If you keep the roots wet at a time when root damage is likely, you may kill the pest but end up with the plant rotting - hardly a happy ending.

Killing? If you want to avoid the nastiest chemicals then I recommend meths and neem oil. Meths as a contact insecticide and neem as a systemic insecticide. With meths, probably no need to dunk, just use a good spray.

Minimising reintroduction? Yes, wash all the pots, especially the underside and round the top, and the staging and under the staging. Utterly laborious but necessary. Perhaps using a dilute disinfectant. To stop reintroduction, yes, check all new plants, and keeping pots from touching each other can also slow any spread (and reduce the likelihood of fungal infections by increasing airflow)

Hope some of that helps

Mike