Please help. White fluffy infection and brawnish spots

[Pluisje]

Dear all,
Can someone help me with identifying the problem with my cactus, please.
This one is very dear to me.

I have treated it several times (with a week interval) with a triazole fungicide (Tebuconazole), but it didn't help.

Thank you in advance.
Svetlana

PS Note, it has a natural pretty white pattern on the body next to these ugly fluffy particles and brown spots.

[gemhunter178]

It's the mealy bug- I myself haven't had them-yet,but I read you can just rub them with rubbing alcohol, I don't know if this hurts the plant though. Also, I hope you isolated that from other cacti, they can spread.

[luddhus]

Remove as many as possible with tweezers first, then spray the plant with alcohol, isopropanol or ethanol. I think your plant can withstand 100%, but if you want to play safe you can go down to 70 %. Watch the plant carefully over the next month and repeat the treatment if necessary. This is usually enough when there is just a few bugs present, but in your case (which is severe) a systemic insecticide could be useful too.

[Pluisje]

Thank you both very much for useful suggestions.
I looked up for more information on the mealy bug and the good news is that the chance of survival is not too bad.
Yes, I isolated the cactus together with its neighbour suffering from the same bug.
I will follow your instructions, thanks a lot!

[iann]

I can pretty much guarantee that if you pick off every visible bug and spray the whole thing with rubbing alcohol, then they will be back again within a year

[Pluisje]

What is your suggestion, Iann?

[iann]

What is your suggestion, Iann?

Systemic insecticide. Otherwise you could try spraying every few weeks for ... six months? Wouldn't kill root mealies though.

[daiv]

I concur with Ian: Physical removal is not enough. They are tenacious and I've always had them come back without using systemic.

[Pluisje]

Thanks for your replies!
Yesterday I removed the bugs mechanically, brushed off with ethanol wiped toothbrush from the difficult places and then sprayed with Thiacloprid.
I am now excited to see the results.

[Steve Johnson]

Thanks for your replies!
Yesterday I removed the bugs mechanically, brushed off with ethanol wiped toothbrush from the difficult places and then sprayed with Thiacloprid.
I am now excited to see the results.

I use Imidacloprid, but I think that's basically the same as what you're using. However, spraying doesn't last long, so it would be better to use Thiacloprid as a soil soak. A systemic approach is much more effective because the plant's juices become toxic to mealies, and it should last for a few months. Better yet, it also takes care of root mealies -- all you can see right now is above-ground, so who knows what may be lurking in the soil.

Two things:

1. I don't know if the Thiacloprid spray has the proper dilution rate for using as a systemic. I can only go by what I'm using with Imidacloprid. My preferred choice is Bayer Advanced Complete insect killer with 0.72% Imidacloprid. Ratio is 1 tablespoon Bayer Advanced per quart of water thoroughly mixed. If this corresponds with your Thiacloprid, all you need to do is take off the cap, pour out the proper amount of liquid, then dilute in water. If you have any concerns about the dilution rate, find out if other members on the forum can give you further advice.

2. A soil soak won't do any good right now since your cacti aren't taking moisture in the roots. Spring is the best time, and I'd say early April. If you can put up with spraying a little longer, go for the systemic when your cacti are underway in the growing season.

Hope this helps!

[Buck Hemenway]

Just a note. the little bugs have a gestation period of 8 days. You may kill all of the active larvae and adults with a contact spray, but not the eggs. Every 8 days for three cycles will do the job, or the systemic way is the best.

I have expert grower friends who will unpot such a plant, clean off all of the soil and submerge the plant, roots and all in a light dishwashing soap solution. Minimum 30 minutes, up to several hours. The plant does not mind and the bugs, eggs and all are either killed by the water, or the soap which melts their exoskeletons.

[Pluisje]

Thank you all for all the useful advises! They are really very much appreciated.
I feel like after the treatment I need to give it a rest right now (?). Just to give it a good spring start. I don't dare to touch the roots now .
Perhaps a good idea to spray every 8 days for three cycles, thanks Buck Hemenway.
I will observe it closely, may the bugs come back I will do the soil soak or something like this later, in the spring, when my plant is a bit stronger.
Thanks everyone!

[dattdude]

Bacilus thuringiensis in the water might work to kill bug infestations in the soil or roots. They are doughnuts sold as mosquito larvae killing insecticide in all the gardening stores. It works by attacking the digestive system of mosquito larvae so it probably kills any bug larvae. it is environmentally friendly as well. I just drop a doughnut in my rain water barrels every 3 months.

[Pluisje]

Very intresting idea! Thanks for sharing Dattdude!