If you rely on winter weather to kill pests, you may be left out in the cold

November 29, 2008|By susan.reimer@baltsun.com | susan.reimer@baltsun.com,susan.reimer@baltsun.com

This month's cold snap was a welcome event in my garden. Finally, I thought, we are going to have a nice, harsh winter with temperatures in the teens every day and a crippling snowstorm or two.

But the cold did not last, and moderate temperatures returned with a vengeance.

My hope that Mother Nature would kill off the bugs and spores that overwinter in my garden appeared dashed.

Dashed, and, it turns out, misplaced.

We haven't had a really cold winter in Maryland since 2003, when temperatures averaged below freezing at 30.9 degrees. Since then, temperatures have averaged well above freezing for December, January and February, as high as 37.2 in 2006.

Certainly there were plenty of cold days during those winters, but the season has been, relatively speaking, warmer.

"We haven't had any sustained cold in five years," said Carrie Engel, greenhouse manager at Valley View Farms in Cockeysville. "My alocasia came back two years in a row, and my friend Nancy was just saying that her caladiums had come back in a pot! And that never happens."

Engel and her friend may have derived some benefit from this warm weather, but I blamed it for the vitality of the insects that chew my coral bells into lace doilies and for the fungi that have attacked my black-eyed Susans and for the rust on my hollyhocks.

As it turns out, I'm wrong.

"These diseases have evolved to withstand pretty extreme conditions," said Jon Traunfeld of the Maryland Cooperative Extension's Home and Garden Information Center. "And any insects that are overwintering that can move will move deeper into the ground and others may be protected in egg sacks underneath the bark."

Traunfeld sees evidence of global warming everywhere. Growers are enjoying a longer season and can get an earlier start in the spring, he said.

"And I don't even protect my fig tree anymore, and I have been OK," he said.

Kathy Purdy, who blogs on Cold Climate Gardening and lives north of Binghamton, N.Y., says temperatures are in the teens most days during her winters and the ground freezes to three feet. She hasn't found that to be much of an advantage when it comes to insects and disease.

She thinks drought - and that can include the lack of snow in the winter - has made plants more vulnerable.

"You might not see it that year, but you will see it the next," she said.

Gene Sumi, education coordinator at Homestead Gardens in Davidsonville, says the key to restraining insects and disease in the garden is "garden sanitation."

It is up to me to remove the infected foliage and rake the beds clean and do some dormant spraying, he said.

"That won't take care of everything, but it will eliminate a major part of it," said Sumi.

Spores, he said, can encapsulate themselves and survive the toughest winter "only to explode in the spring and reinfect everything."

Spider mites can continue to do damage in the winter and are ready to do even more damage in the spring, he said.

He recommends an old farm remedy - lime sulfur spray. Farmers used to make it themselves; it is nontoxic and organic.

"It only has three problems," said Sumi. "It is a messy job, it looks bad and it smells bad."

The spraying must be thorough - "every nook and cranny," said Sumi. And the result is the foliage looks like it is covered with runny plaster, and, because of the sulfur, it smells like rotten eggs for a couple of days.

Lime sulfur spray is one of the safest fungicides, according to advice from High Country Gardens' experts, and also works to control insects. It can be used against peach leaf curl, brown rot, leaf spot, powdery mildew, rust, black spot and blight, as well as mites, scale, borers and aphids.

Dormant oil spray is another way to control pests, especially on roses and evergreens. (The two products should not be used at the same time.)

It can control aphids, whiteflies, scale, mites, mealy bugs and some caterpillars by suffocating adults and smothering eggs. And again, thoroughness is important. Pests like to hide on the underside of leaves.

So, instead of reading the Farmer's Almanac and hoping for bitter cold and heavy snow, I should be out in the yard during these mild days, cleaning up and spraying.

The garden teaches another lesson: I can't count on anyone else - including Mother Nature - to do my work for me.

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