Nasty rust, or just innocuous scale?

Controlling pests of bamboo

Moderator: needmore

Post Reply
Saklo
Posts: 20
Joined: Wed Jul 03, 2019 12:26 am
Location info: 0
Location: S. Florida, Zone 10

Nasty rust, or just innocuous scale?

Post by Saklo »

Greetings -- I'll try to keep this long tale brief.

Two years back, as a novice, I brought home a Bambusa propagule unaware of its serious pest infestations. The first bugs I noticed were the bamboo mites, due to their nests. Also on the leaf undersides: pale, immobile scaly things not much bigger than the roaming mites. I hosed the plant down a couple of times with a pyrethrin/oil treatment that put the hurt on the mites, but the scaly things seemed unaffected. I also noticed that these waxy bugs were thickest on leaves that were streaked with red and rather pale in color.

After staring at a lot of online images and taxonomies, the best I could figure was that I was looking at the "uredinia" -- that is, the spore-producing structures -- of a bamboo-specific rust named Kweilingia divina. I learned more about this Kweilingia -- it seems the California authorities rate this a serious, destroy-on-arrival pest, and that they had fingered the very nursery where I'd gotten the plant as an infestation source on more than one occasion. I did two things: burned the plant to the ground, and sent foliage to my state extension biologists for a positive ID. (I also alerted the nursery, but that's another story.)

The plant rebounded, but on its new leaves the waxy little bugs are again present. Meanwhile, when the state got back to me, the report IDed the mystery bug as a common pit scale, Bambusaspis miliaris. I'm not convinced -- what I can find on that pit scale says they're round-shaped and twice as large as what I've got, and if they were scale, I assume the pyrethrin/oil treatment would have had some effect, and it hasn't.

I've attached two (pre-apocalypse) photos of the leaves with their original mite damage and nests visible. The upper-side view also shows what I suspect is the rust, and the underside shows what I believe to be the rust pathogen -- waxy, pale, elongated specks that are all oriented parallel to leaf length. Sorry I couldn't get a closer view.

I welcome anyone with any experience or suggestions to offer their two cents' worth. I want to be rid of it, whatever it is, before it migrates to my Dendrocalamus. Many, many thanks!
Attachments
Leaf underside
Leaf underside
Leaf upper surface
Leaf upper surface
Saklo
Posts: 20
Joined: Wed Jul 03, 2019 12:26 am
Location info: 0
Location: S. Florida, Zone 10

Re: Nasty rust, or just innocuous scale?

Post by Saklo »

To supplement my previous ramble, here's an unscaled closeup view of the underside image, with identifiers. The mites and their nests, as I said, have been eradicated, but the elongated squatters persist, along with the spotty and streaky red bits on affected leaves. The leaf here is about an inch wide at most. I didn't really notice these things until I used a magnifier. Anybody recognize these things?
Attachments
Closeup view of underside
Closeup view of underside
Post Reply