What is the best way to learn about tree pests, infections, etc

[Unagi]

Hi Everyone, What is the best way to learn about tree pests, diseases, etc? (identification, treatment, prevention, etc)

I have a chinese elm with the issue below. I have only noticed it yesterday evening, and I have no clue what it can be, or how to treat it. I now checked my other chinese elms (both normal and cork bark) and I think they might start to have this as well. On some leaves, there are smallish half-transparent spots.

I still dont know what this can be, I do not know how to search for this on the net. The trees are on my balcony, it cannot be snail.

 

[Unagi]

Well, I know one source: the ophthalmologist. I opened the pictures to check if you can see details, when I noticed a small, green caterpillar on the last one. Oh my gosh, facepalm. I quickly went to the tree and checked it again, and I almost missed it. They are really difficult to spot.

Anyhow, the question still hold, what is the best source? (book, website, wiki, forum, etc)

 

[Notsureaboutplantnames]

Us this site. UC Statewide IPM

Find your local Ag Extension office for local pest issues.
https://npic.orst.edu/pest/countyext.htm

Otherwise the key is diagnosis of plant problems which can be very difficult but quite educational.

One thing I see is some slight skeletonization of on the leaves. which is usually some sort of moth/butterfly larvae.

The other option is to look for pests and diseases of your particular plant. (use the UC Link again)

 

[penumbra]

Most any plantaholic, bonsai and otherwise, should consider checking if there local community college has classes pertinent. I really loved entomology as it relates to horticulture. Plant pathology was great too, but a little more complex for me. Still, they were great moves on my behalf.