Problem with Rebutia

[HaoBao]

Hi all, does anyone have an idea what is causing this discolouration on my Rebutia?

Is it red spider mite?

[anders]

That would be my first guess.

[esp]

That would be my first guess.

Agreed

[HaoBao]

Oh dear, I wonder if it came from this Opuntia plant?

Should I just bin the rebutia? There are a few other rebutias that were next to it that look similar but not as far gone.

Don’t know if it’s possible to separate them and keep treating them and try to take off some clean new growth?

Does anyone know if the concentrated Bug Clear Ultra treats Red Spider Mite? The spray gun variety says it does on the bottle but the box of concentrate doesn’t mention them.

Also, would using the Bug Clear Ultra as a systemic insecticide work against RSM?

This discolouration on the rebutia seems to have gotten worse recently. I keep them indoors and give them less water (and therefore less Bug Clear Ultra in the water) over the winter.

Flipping bugs!

Thank you for the advice

[Terry S.]

Red Spider mite tends to concentrate around the growing points so that is just corking on the opuntioid.

It is debatable as to whether any insecticides available on the amateur market are useful for killing red spider. I tend to give fortnightly sprays with SB Plant Invigorator to kill them. The spray is not a chemical insecticide and is safe to use in a dwelling house, it kills the adult bugs by suffocation. It does not kill eggs which is why repeat sprays are necessary. This should also give you some control against other pests as well as providing a little "foliar" feeding. It is probably OK on most leaves with farina, but I don't grow many of these to be able to be sure about it.

[MikeT]

]

Red Spider mite tends to concentrate around the growing points so that is just corking on the opuntioid.

I agree with Terry. It looks as if the Rebutia has new, undamaged, growth on several of the heads, in which case the rsm that caused the damage had already gone by the time the new growth occurred. The plant should grow out the damage in a few years, or break it up in the spring to propagate some new plants.
New damage appearing at and around the growing point indicates current rsm. The trouble then is that significant damage has already occurred by the time you notice anything.

[Stuart]

I'd agree with Terry about SB Plant Invigorator, I only started using it last year but it works well against RSM and mealies. It does damage farina but that soon grows out and it does need to be used regularly until all eggs have hatched. When used from the concentrate form, it's fairly inexpensive. SB isn't easy to find, not widely available and I've never seen it advertised. I've bought the concentrate from Webbs in Wychbold near Birmingham but even there it's hard to find, amongst the orchids rather than with all the other insecticides. If in the right area, it's available to buy at BCSS Brighton and Rother Valley branch meetings when they recommence.

Stuart

[Terry S.]

I usually buy my concentrate from RHS Wisley Garden centre. It works out at about £16 for 50 litres of resulting spray, which usually lasts me for a season. Note that there is an ultra-concentrated form available to the horticultural trade, which I guess does not require a spraying licence to buy, seeing that it is not a chemical control. The ready-diluted sprays are going to be expensive.

Yes I agree that the Rebutia is probably now mite-free. I got a plant of 'Apricot Ice' in this condition from a branch raffle two years ago and it has now grown to cover all the damage.

[Phil_SK]

For a single plant, it's easy to fully submerge it in half a bucket of water with a bit of washing up liquid in it for 5 mins, followed by a quick rinse. Cacti cope with this just fine, though you might not want such soggy plants in the dormant season.

[juster]

I've used SB for many years with good results. If it's not with the insecticides, then I've seen it for sale in the vegetable growing section, so worth checking there.