Hello,

I have a bunch of wisterias (1st year), potted in 100% akadama, outside in full sun (up to 40 degrees Celsius).
I water them daily, I also put water in a deep tray.

Regularly, leaves turn yellow and whirl.
Upon closer inspection, during the night with a flashlight, I spotted that each affected leaf has web at the base and some insects.
New shoots are green.



I spray with insecticide, and it kills them for a while.
It’s like they keep coming back.
I have a bigger wisteria next to them, which is in normal soil. This one isn’t facing this issue.

Question is: why do the small ones have this issue?! Is it from my watering, from akadama, are they too young for this amount of heat?

Pests also have preferences when it comes to what plant to attack. Spider mites normally thrive in hot and dry conditions and go for already weak plants. Maybe this tree is still in repotting stress? Maybe you did not keep up with watering? Maybe you did not get fertilizing right?

I am not a fan of akadama at all. But it is not to blame for bringing spider mites to your tree, they cannot survive in soil without a host for very long.

Note that spider mites are not insects, so an insecticide will not kill them. Use a product that explicitly mentioned spider mites. And remember the repeat period. Normally 4-6 weeks. But if it is that hot, I would probably use 3 treatments, 2 weeks apart.