Garden Q&A: Kill the miscanthus but choose least toxic approach for pests

My neighbor lives next to an unused farm field where clumps of this grass have been spreading for years. This year it showed up in her yard. It’s between 6-8 feet tall. Is this invasive phragmites? The field is not particularly wet, and that likes wetlands, right?

This is miscanthus, another ornamental grass gone bad. Notice the somewhat curled seed heads. Miscanthus can be highly invasive in wetlands, but is not picky about soil wetness, as you’ve seen.

Some miscanthus species are touted as “safe” because supposedly they ripen seed late so it never matures to be a problem. However, with our longer seasons of warm weather and rampant hybridization, all bets are off for miscanthus. It shows up everywhere these days.

Kill it. Compost stalks but not seeds. Keep an eye out for more seedlings. If possible, alert the owner of the field as well as other neighbors. (Incidentally, phragmites can grow very nicely without damp soil and often gets introduced in fill dirt. It has a more upright seedhead and will cover vast areas in a solid blanket.)

I got into using a company for tree and shrub insect and disease control when my arborvitae had a very bad infestation of bagworms. I pay for four pesticide sprays per year. I wonder if I need to do this anymore? I have not had any bagworms for over four years. Would I be safe in discontinuing all applications? I hate using these things but am afraid of losing my arborvitae.

When shrubs are growing well and pest/disease problems are under control, no preventative treatments are needed. We recommend “integrated pest management,” the approach which seeks the least toxic solution.

This begins with being familiar with plants -- their growth habit and conditions they need. Take a stroll occasionally, monitoring your plants. If you see a problem, first figure out the possible causes. (We can help -- you can send us photos.)

Half of problems are not caused by either insects or disease. When it is a pest, learn the life cycle and the best time and way to take action. For bagworms, for instance, start monitoring for tiny ones in May. There is plenty of time for control. Search ‘bagworms’ on the University of Maryland Extension’s Home and Garden Information Center website for easy tips.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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