I have recently noticed many small black flies/gnats congregating in the soil of a number of my bonsai…from maples to spruce.
I live in Sacramento, have been watering a lot due to high temperatures and recently started using organic fertilizers which I simply spread on top of the soil. After reading online, I am guessing these are fungus gnats attracted to the moisture and fertilizer. I could be mistaken and would be interested in other thoughts.
I will remove the fertilizer today and try watering less.
The questions: Can I use an insecticide? If so, recommendations on which one? Can it be applied in this heat? (90’s - low 100’s).
Thanks for any input.