This morning I noticed some yellow crystals on my two-year-old Eureka seedling's stem. I initially thought it was dried honeydew and removed them, but couldn't find aphids when I checked the plant. Now I believe it may be early symptoms of phytopthora gummosis, as those pictures seem to match most closely? There were only a couple of crystals but I went ahead and sprayed with some basic fungicide.

Is there anything else I should do?

The tree's put on a ton of height and new growth this spring, and soil hasn't been over-moist--it's a well-draining perlite mixture. Really not sure how the fungus got a foothold to begin with, if that's the problem. Will try to add pics if the crystals return (hopefully not)