Commiseration and $5 will get you a small Starbucks coffee.

The first, and probably most important step, is to be sure of your diagnosis, and the extent of it's spread.

Brown spots on foliage are not one of the identifying effects of Miscanthus Mealybug. They are, however, a possible indication of Miscanthus Blight.

External plant damage from Mealybug can be reddish-purple streaking and spots, but it isn't common.

Get in contact with the local County Extension, and see if they can help with ID and with suggested controls. Mealybugs, in general, are controllable scale insects. When you can see and hit them, plain old insecticidal soap can control them. Unfortunately, Miscanthus Mealybug hides out of sight, between the stem and sheath, and can't always be hit with a topical solution.

The bad news about this bug is that isn't easy to control, but it can be controlled with effort, and the good news is that it seldom, if ever, migrates from plant to plant. If you divided an infested plant, you have that many more infested plants, but the critter won't generally move from plant to plant, if the plants aren't touching each other.

Use Google to do some research. Learn the life-cycle of the bug. Pregnant females over-winter in the crown of the plant. There are 3 hatches of crawlers each year, mid-spring, early-summer and late summer. Early-spring soil drenches with imidacloprid (Merit, Marathon, Bayer Advanced and others) can interrupt this life cycle. Repeat every ~20 days through the growing season.

Experiments were done last year at U.Maryland, on hot water immersion (120F for 20 minutes) of infested plants from Kurt Bluemel, I couldn't find results, but if you contact the university, and/or Bluemel, you may get some information.

So, IF it's mealybug, the world will not necessarily end, and you may not have to destroy plants. ID and isolate infected plants, and go to work on killing the critters. They don't kill the plants, but just stunt their growth, which we do to Miscanthus every spring anyway. Soil drenching with chemicals or hot water is much easier to do with potted plants.

These cultivars were the most mentioned I could find as having been affected:

'Puenktchen' (Little Dot)
Miscanthus purpurascens (Red-leaved Miscanthus)
'Sarabande'
'Silberspinne'
'Kirk Alexander'
'Malepartus'
'Adagio'

Good luck.

Thanks Donn:

I'm quite certain of the diagnosis -- peeling back the leaf sheath reveals the white webby layer as well as the sap of the mealybugs -- not to mention that the mealybugs themselves are visible as well. I am really amazed and rather sad to see that my stock is so widely affected/infested. 'Strictus,' 'Little Big Man,' 'Malepartus,' 'Gracillimus,' 'Wetterfane,' 'Goldfeder,' 'Little Nickey,' 'Red Feather,' all affected. Quite amazing really. Perhaps they have blight as well -- I guess I wouldn't be surprised at this point. All this leads me, sadly, to have less trust and appreciation for Miscanthus in general. As I look out at my plants and see the Panicums and Pennisetums and others that do not suffer from this malaise, for the moment at least, I feel more appreciation for these varieties. This is not to say that I don't absolutely love the Miscanthus that are in the ground in my yard -- I do.

Thanks again for the input and advice.

Because you are intending on selling your grasses, you need diagnostic and treatment advice from other than the Master Gardeners at your county's Extension Service.

But do call the Extension Service. The Washington County office is in Beaverton, the phone number 503-725-2300. Ask for the Master Gardeners and, when they answer, ask them for the phone number of the Small Farms Agent. (The agent for our region is located at the North Willamette Research and Extension Center.) Tell them you are getting ready to sell ornamental grasses and you need advice for a pest problem and its treatment.

Thanks for the advice Jean. I'll give it a try. So sad that my plants have this pest! Unfortunately, I'll not be able to think of Miscanthus the same again.

i'm back after a long absence to say with certainty that I now have several hundred Miscanthus of at least 10 varieties that have serious Mealybug infestation. They were treated with a granular application of imidacloprid in early August which seemed to knock the critters back but not out. I'm discouraged and my plans to become a specialty seller of ornamental grasses is on hold while I try and sort out how to proceed from this point. I'm thinking of discarding many plants and holding back only small blocks of the finest Miscanthus cultivars for division and re-treatment next spring. i'm contemplting treating with Safari this next round and am wondering if there is anyone out there with experience tackling this critter and wiping it out. If the thought among experts and serious growers is that I'll never be able to sell these plants with a clear concience about the health of the plants i need to factor this into my decision making.

Just know this -- mealybug is out there and it must be more common than people realize. What I wonder is -- is this pest similar to aphids in that it really won't hold back a healthy miscanthus in the ground but does have a noticable effect on plants in pots that are by default under more stress than landscape plants? That is my current thinking. Still, I cannot sell these plants knowing they have this pest! Any thoughts appreciated.