A close-up:



With all his friends:



For a size persepctive - this is a p.bambusoides leaf:



And this is what the top of the leaf looks like and the damage they seem to be imparting:

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"The Way is in training" - Miyamoto Musashi

I've been seeing these brown spots for years and have been mystified at what was causing them. This is the first year I've ever actually seen any bugs. They aren't affecting very many leaves overall, maybe one or two on each main branch. With this mild winter my Madake is looking better than it ever has before though, and I'd hate to lose it to an insect problem.

The logical follow-up question is - how do I kill it? The plant is really too big to do a thorough job spraying the underside of each and every leaf (unless I can borrow David's jetpack sprayer!), so I'd prefer some sort of systemic insecticide.

Any ideas???

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"The Way is in training" - Miyamoto Musashi

I'm thinking Bamboo mite.I had them on my red margin when I brought them in the house in Nov. I then ended up putting them in the ground the second week of Dec; luckily it was a mild winter. I sprayed them heavy with the hose and it seemed to work. From what I have read , they don't harm the plant, just make the leaf look ugly. Sul.

These are aphids. They can reproduce pretty quickly. They live by sucking sap from the plant.
If your bamboo grove is not too large, you can spray it water often to keep them under control. Spray the ground afterwards too to wash away those bugs otherwise they might try to climb back up.

The ones in the photos look naked, but in some seasons, they may develop wings as well.

Yeah, these are aphids. Ladybugs will eat most of them.
Leaf damage is quite severe, I'm not sure if aphids alone could cause that.

Agree on the aphid ID, but disagree that spraying with a strong water stream (a common way to remove aphids from infected plants) will be effective on a plant as large as this. The idea is that you wash them off the plant and they die before they can get back to it. If you just move them to another bamboo leaf, you may be spreading the infestation -- doing more harm than good (or so it seems to me). Insecticidal soap works on aphids, but I'd probably try a systemic like you said.

Interestingly, I've never seen aphids on my bamboos. Maybe I'm not looking closely enough, or maybe there are enough predators to keep them in check.

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Alan.
My blog: It's not work, it's gardening!

Thanks for the quick response! It's hard to see in the pics, but the bigger ones do have wings. Is there any way to encourage/transplant ladybugs? I'm all for natural control if possible, but will probably still do the systemic. Any ideas on what to use?

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"The Way is in training" - Miyamoto Musashi

When you only have a few individuals, lady bugs can keep them in check. But what you have is an infestation, and lady bugs can only eat several aphids per day, unless you have an army of lady bugs, which is not likely to happen. You're better off killing the aphids yourself. Spraying with water will dislodge most of them. But like I said, you need wash them away afterwards.

Matt if the infestation gets to big for "natural" control check out Merit by Bayer (Iclopromid I think).
MarCat

Ladybugs lay eggs on infested plants. Their larvae is ultimate aphid killing machine.

But yes, if there are many, you should use systemic and eradicate their population completely.

This is for my record as much as anyone else having this problem:

I applied Bayer Advanced 2 in 1 Systemic Rose & Flower Care ready to use granules today ($7.92 for 5lbs at Lowe's). The active ingredient is 0.22% Imidacloprid, and I applied it according to their reccomendations for bushes (2 capfuls per foot of height). It says it will protect and feed (6-9-6) for up to eight weeks.

I'll report back in a week or two and we'll see how it does.

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"The Way is in training" - Miyamoto Musashi

Follow-up: After one week I'm seeing dramatically fewer aphids under the leaves, but there are still a few there. Does anybody have any thoughts on how to decide when you need to reapply vs when you need to be patient and just let this stuff work? Can you use too much if you reapply?

I'm leaning toward giving it another week and seeing what happens...

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"The Way is in training" - Miyamoto Musashi

I also have lots of questions about this type of systemic. How much to use? What's the best time to use it for mite control? How often should I apply? I have the liquid Bayer product, and never know what strength or quantity to use. Should I apply as new culms start leafing out? (Apply to soil, not as a foliar spray)

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Alan.
My blog: It's not work, it's gardening!

Update: after two weeks I've got to look really hard to find one of these things. They're still there, but there are maybe two or three per plant instead of 20-30 per leaf. This stuff seems to work as advertised.

I think I'll continue to watch it and only reapply if their numbers start to swell again.

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"The Way is in training" - Miyamoto Musashi