Beginner Gardening: Help please: Black rotting spots on my Bodhi tree leaves! , 1 by PatrickA_FL

PatrickA_FL wrote:
Hello everyone,

I am hoping that this post isn't misconstrued as obsessing over my tree, but today I have found what I believe to be fungus gnats on the foliage of my tree. I have done my research and have learned that these little pests are due to over-watering. I also have reviewed their life cycle and I also have learned that I need to let the soil dry out between waterings down to about 3 inches minimum. No problem. I have also read about yellow sticky card (AKA "Gnat Stix") control for the adults as well as pyrthroid based agents such as bifenthrin, cyfluthrin, permethrin, and lambdacyhalothrin. I also have read that Bacillus thuringiensissubsp. israelensis handles the larvae in the soil, although it doesn't sound like it is readily available in retail markets. I did read where "the systemic insecticide imidacloprid will also kill fungus gnat larvae when applied to the growing medium. This active ingredient is available in a number of houseplant insecticide formulations as granules, slow-release “spikes”, and in combination sprays with a pyrethroid-based insecticide".

What I haven't been able to uncover is any information as to their destructive payload. Is this possibly what is causing the white spots as shown below in the next post? Do the adults feed on the foliage? I have found two adults already on the foliage and I just looked at one leaf so far.

By the way, I switched to the following growing medium one week ago:

3 parts fir bark
1 part sphagnum peat
1 parts coarse perlite
2 parts fine Miracle Grow Perlite
Small amount of Black Kow brand composted manure.

I watered the new mix in and applied Miracle Grow 3-1-2 ratio fertilizer (24-8-16) as recommended by Al.

Does anyone know which steps (other than allowing the soil to dry out) work best for fungus gnat control? Preferably something I can get at one of the big box retail garden centers?

Would appreciate any and all suggestions other than to simply "stop obsessing" over my declining tree. That was a bit offensive as I came to this forum as a self-professed horticulture novice seeking professional help with a legitimate problem on the ONLY plant I own. This tree is important to me and to just wait and see what happens to it knowing that I have a persistent insect issue at the very least, is unwise in my opinion. I am a medical professional by trade and treating all possible causative factors of disease is in my blood, I suppose.

Again, thanks to everyone who takes the time to reply with genuine, sound advice.

Cheers,

Pat





This message was edited Jan 24, 2012 11:07 AM