Weather can make grass more susceptible to fungus

January 01, 2012|By Ellen Nibali, Special to The Baltimore Sun

My grass has tiny orange raised bumps on the blades. It started about the beginning of fall. It seems worst where there is more shade and the ground stays moist longer. Will it kill the grass? Numerous blades are completely covered. I fertilize a few times a year, using the recommended amount for my bluegrass.

Kentucky bluegrass and perennial ryegrass are the grasses most susceptible to rust, a fungal disease. Rust disease is favored by low nitrogen fertility, but this is probably not your cause.

Cool, moist, overcast weather from late summer to early fall also favors rust, and we had this weather in spades this fall. Rust can even occur late in fall and through the winter if air temperatures are moderate.  Fortunately, it does not kill plant crowns. Turf may thin but should come back in the spring.

It is too late to spray fungicides. Fungicides are preventive and will not "cure" an infection. When you mow rust-infected grass, remove the clippings. In the future, plant turf-type tall fescue, which is highly resistant to fungal diseases.

I recently received trees and shrubs from a charitable foundation. Instructions said to remove any grass three feet around each one. Could you possibly explain this? I have not done it before. Is that why my plants take such a long time to grow up?

Grass is a strong competitor for moisture and nutrients when young trees and shrubs are planted into an established lawn. Grass roots can intercept rainfall before it ever gets down to tree roots. The mat of turf roots can also monopolize fertilizer nutrients.

Remove a generous circle of sod around new plants, then apply a thin mulch layer over the bare soil to help insure that water and nutrients are available as plants struggle to get established. This also keeps heavy mowers from packing down the soil over tender new roots.

View our publication, Planting Tips for Trees/Shrubs, for more information at:

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question from the website at

Plant of the Week

Dwarf oriental spruce 'Barnes'

Picea orientalis 'Barnes"

Dwarf conifers are a huge asset to the winter garden, because they are lovely year round. Oriental spruce 'Barnes' is one of many choices. Because it grows very slowly, only one to three inches a year, Barnes rarely needs pruning. Given time, it can reach three feet high. Keeping good green color all winter long, Barnes has short half-inch needles arranged thickly on upright short branches and a ball-shaped globose form. A native of Asia, it prefers full sun and rich, well-drained soil. Once established, it tolerates dry soil and is not a favorite food for deer.

– Ginny Williams

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