Nasty rust, or just innocuous scale?

Controlling pests of bamboo

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Saklo
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Joined: Wed Jul 03, 2019 12:26 am
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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!
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Leaf underside
Leaf underside
Leaf upper surface
Leaf upper surface
Saklo
Posts: 22
Joined: Wed Jul 03, 2019 12:26 am
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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?
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Closeup view of underside
Closeup view of underside
fredgpops
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Location: plus 700ft in the Santa Cruz Mtns, 8 miles from the Pacific
35 miles S. of San Jose

Re: Nasty rust, or just innocuous scale?

Post by fredgpops »

Looks like bamboo mites to me. Last time I had them I sent pictures to 3 bamboo nurseries to confirm and ask for recommendations to reradiate. I'd recommend this method. The mites don't kill they just make the plants ugly. As I recall you are in the South. ABS can help you identify bamboo nurseries near you. A bamboo nursery in the South gave me good info on eradication. I went with what may be a non-standard option so I'll pass on what was best for me. Rgds
Saklo
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Location: S. Florida, Zone 10

Re: Nasty rust, or just innocuous scale?

Post by Saklo »

Hello Fred, and thanks for the reply (a reply!!). Well certainly there were mites on the plant -- individual mites and their cloudy, silken nests are both indicated on the photo above. My concern is with the other thing in the photo, labeled "mystery pest" -- the waxy, pale, elongated things that are larger than the mites, but smaller than the nests pictured. I've become pretty good at spotting mites and eradicating them because my local nursery is infested with them. This mystery pest, however, is resistant to all those treatments.

As for your suggestion, naturally I first turned to the nursery. I went so far as to take back sample foliage and a magnifier so they could take a look. I even took the nursery employee on a tour of the grounds and pointed out lots of places where both these pests were abundant. The initial response was "we kind of like to let nature take care of these things on her own," but I was assured that the boss would get back to me to discuss my concerns, and possible treatments. Nothing of the sort ever happened, even though I made several follow-up calls. The only feedback the nursery ever gave me was the same employee offering the standard corporate "we'll give you a refund if you're not happy." It took two weeks to get that trifle.

I still suspect I'm seeing Kweilingia rust spores -- the U. Hawaii has an image of similar spores at https://gms.ctahr.hawaii.edu/diseasespe ... moid=33915. Also see the leaf-underside image on page 3 of their write-up at https://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-74.pdf. Considering how easily this bug escapes detection, the obscurity of this recent arrival and the attitude of my local nursery (which ships nationwide), I'll bet quite a few enthusiasts are hosting this thing, quite unknowingly. It's an A-rated pest (highest concern) according to the state of California, and seems to prefer Bambusa, Dendrocalamus and Thyrsostachys among the clumpers.
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