Small black bugs in the medium

[plantlady]

I've been scratching my head trying to figure out what these little buggers are. They are black in color, and very small, much smaller than all the common pests.

I started noticing them in some phragmepediums that I have growing in semi-hydro culture. When I water the medium I occasionally see them exiting through the drainage holes and into my humidity trays.

Sometimes they appear to float on the water and they can even jump. Other times I've seen them actively moving around the insides of the pot.

My solution was to place my orchids in a well ventilated are and drench them with Ortho Systemic Insect Killer. It did not harm my plants and I have not seen the buggers return yet.

My fear is that they are root aphids, however all pictures online of root aphids do not resemble these insects in size. And the best guess that I have is that they are flea beatles, however I have not been able to accurately identify what they are and am curious to see if anyone else has this problem or perhaps knows what these curious little insects are.

[Ross]

Look at them carefully (a hand lens helps) if they have two "antenae-like things on the ends, they are shore fly larvae. See: UC IPM Photo for the larvae. The adults are powerful fliers, but seldom fly. They run very quickly. The good news is they have an exclusive diet that does not include any part of your orchids. The bad news is there is no ready spray-type cure. The source is algae and diatoms in the medium. Even newer medium will quickly colonize. The Ortho stuff probably didn't rid them. I think you are in a phase between pupae and adults. Just a guess. But see if you can identify the larvae. The little eye appendiges are visible to the naked eye.

[whygreenberg]

Hmm...this is very interesting. I've recently seen some of this activity in the medium of one of my rupicolous Laelias. The gravel is quite green with algae. I'd already ruled out fungus gnat because the fly looks so different. And these are WAY faster. I haven't seen them move to any other plant. Just the one.

[Ross]

Originally Posted by whygreenberg

Hmm...this is very interesting. I've recently seen some of this activity in the medium of one of my rupicolous Laelias. The gravel is quite green with algae. I'd already ruled out fungus gnat because the fly looks so different. And these are WAY faster. I haven't seen them move to any other plant. Just the one.

You are right on! Not fungus gnat (that little guy could be a problem.) The algae is the key. I don't think from all the reading I've done on the Shore Fly, that I would worry. All the texts say the prevention is the cure - get rid of the algae. Now we know that is not going to happen all that easily, especially in an Orchidarium. But like I said, they don't seem to harm the plant or roots in any way.

[plantlady]

Thanks for your input! I am familiar with shore flies and their larvae and can safely say that these pests are not related to shore flies since they resemble tiny small beetles and their abdomens are rounded like aphids or beetles. I did however find some shore fly larvae in a humidty tray with plants growing in spaghnum! The distingushing feature in between these minute insects is that my bugs have a visible distinction between their head and rounded abdomen.

They do appear to be attracted to the color yellow as I have noticed tiny dots appearing on my traps. In comparison to fungus gnats, these insects are perhaps 1/10 or 1/16 of the size of a fungus gnat. I would post a photo but I don't believe my camera would provide much detail as the insects are extremely small.

My medium is clay aggregate, there is no evidence of algae, diatoms, or other growth on my rocks. The spahgnum is another story.

I believe these bugs came with some phragmipediums that were growing in a greehouse with many other types of plants. I repotted my phrags which were in a firbark medium to the clay aggregate and probably transferred the insects to the clay aggregate.

I found some pictures online of flea beatles and I can say that these tiny little bugs are not flea beatles. However they may be the smallest beatle in the world. Nanosella Fungi