It's too late to stop grubs now

Backyard Q&A

try again next June

In The Garden

October 24, 2004|By Jon Traunfeld and Ellen Nibali | Jon Traunfeld and Ellen Nibali,Special to the Sun

I dug up brown dead patches of my lawn and found an infestation of white grubs, which appear to have destroyed the root system of the grass. Apparently, they are grubs that turn into Japanese beetles. Is it too late to buy a pesticide and treat the lawn? Do you recommend a certain one?

Grubs have been feeding heavily on turf roots for the past couple months, and they have already done most of the damage they will do at this stage of their lives. Now they are burrowing deep into the soil to "hibernate." Next spring they'll come up again, but will feed only lightly before pupating into adults and flying off to mate and lay eggs. Young, newly-hatched grubs are most susceptible to grub control products. We recommend products containing imidacloprid (Merit) or halofenozide. Apply between mid-June and the Fourth of July, so rain or watering moves the chemical into the soil just in time for egg hatch in August. For more information see our online fact sheet, HG-78 The Japanese Beetle.

I planted several canna plants this year for the first time. Do I have to dig up the bulbs and store them for the winter?

In mild areas of zone 7, you can cut the cannas down and heavily mulch them each winter. For sheltered areas, this should be sufficient. Otherwise, wait until frost has killed the foliage, then lift the rhizomes. Dig gently, removing as much soil as comes away easily. Cut stems and foliage back to 2-3 inches and rinse off remaining soil. Let rhizomes air dry for a few days, then place in a paper bag and store in a cool, dark area of your home where the temperature stays between 40 and 50 degrees. In spring, divide the rhizomes into 6-inch pieces, making sure each piece has at least one bud when you replant.

I am a member of a community vegetable garden that tills its soil in the spring. I suggested fall tilling to reduce the insects. We currently have large populations of squash bugs, cucumber beetles, Mexican bean beetles, etc. Garden cleanup does not occur, so sanitation is lax. What do you suggest?

Fall tilling is recommended for several reasons. By incorporating organic matter in the fall -- such as compost, shredded leaves, old mulch, and garden stubble -- you disrupt insects that would otherwise overwinter in garden debris or the top few inches of soil. Plus, you improve the overall health of the soil. Intensify your campaign to encourage better sanitation practices. A thorough cleaning of garden debris (even if it's not tilled into the soil) is extremely beneficial. Pesky insects also overwinter in weedy patches adjacent to the garden.


1. Paint the trunks and main branches of cherry, plum and peach trees with a white latex paint to prevent sunscald and frost cracks over the winter. Keep mulch at least one foot from fruit tree trunks.

2. Spray trees and shrubs that have had scale or adelgid problems with a dormant oil spray. Temperatures must remain above freezing for 24 hours after spraying.

3. Place a straw mulch loosely over spinach, garlic, carrots, turnips and other fall crops to protect them from hard freezes.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at the University of Maryland Cooperative Extension's Home and Garden Information Center. The center offers Maryland residents free gardening information and answers to plant and pest questions. Call its hot line at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail questions to (You can also download or order publications and diagnose plant problems online.)

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