can you tell me what these are?

[Kipody]

and how to kill them?
Thanks

[Ilvin]

Its hard to say from your photo, but I assume you mean the white bits on the spines? They look like mealybugs to me.

Mealybug treatment varies from area to area - I use isopropyl alcohol because the systematic insecticides are quite aggressive and not available in my country. That said, I've only ever dealt with spine mealybugs in ones or twos.

Try this link here: https://cactiguide.com/forum/viewtopic.php?t=42129 for a more detailed explanation on them and how to get rid.

[greenknight]

Yes, alcohol will kill them, as will soap sprays. The eggs will survive, though, and more will hatch out - you need to repeat the treatment weekly until you're sure they're gone. The advantage of systemic insecticides is they have residual action, they will continue to kill the new hatchlings for months.

[MrXeric]

I bought a Ferocactus viridescens earlier in the fall that was infested with mealybugs on the spines. I used tweezers to pick them out and a small paint brush soaked with isopropyl alcohol to remove anything I missed. I watered with a systemic insecticide (imidacloprid) and sprayed the whole plant (I made sure the areole fuzz was well soaked; mealies like to hide in there!) and pot with a contact insecticide (this product https://bioadvanced.com/3-in-1-insect-d ... ntrol.html) overnight. I repeated the spraying 2 weeks later. I haven't seen them pop up again, but it is winter now and the bugs aren't as active. I will repot in spring; there may be eggs and bugs in the soil waiting for warmer temperatures.

[Tom in Tucson]

I bought a Ferocactus viridescens earlier in the fall that was infested with mealybugs on the spines. I used tweezers to pick them out and a small paint brush soaked with isopropyl alcohol to remove anything I missed. I watered with a systemic insecticide (imidacloprid) and sprayed the whole plant (I made sure the areole fuzz was well soaked; mealies like to hide in there!) and pot with a contact insecticide (this product https://bioadvanced.com/3-in-1-insect-d ... ntrol.html) overnight. I repeated the spraying 2 weeks later. I haven't seen them pop up again, but it is winter now and the bugs aren't as active. I will repot in spring; there may be eggs and bugs in the soil waiting for warmer temperatures.

I'm sure you more than likely killed the little buggers, but the "rule of thumb" I've followed for years is; to apply spray every 3 days for 2 weeks for nearly certain 100% eradication.

[MrXeric]

I'm sure you more than likely killed the little buggers, but the "rule of thumb" I've followed for years is; to apply spray every 3 days for 2 weeks for nearly certain 100% eradication.

I don't get mealybugs unless they come in from new plants I buy. Mites on the other hand, is a perennial battle. For those I spray the infected plants every couple days for two weeks at least. One application of miticide is never enough!