A Wet Season Can Take a Bite Out of You

By Adrian Higgins
Thursday, July 17, 2008

If you garden long enough in one place, you realize that no two growing seasons ever match up.

Some years, there are subtle changes: a rare late frost that punishes those who jumped the gun or a tropical storm that brings down an old tree.

In other periods, you wonder if you are living in the same place. This year, for example, with a spring and summer that have delivered abundant rainfall when plants are programmed to grow their most. The contrast to last year's punishing drought makes it all the more extraordinary.

Last fall, I came across gardeners who were spending hundreds, even thousands of dollars keeping water running through hoses as a form of survival gardening. Now, after about 30 inches of rain so far this year, it's a jungle out there. Hoses remain coiled like snakes.

This is mostly positive news. The elusive quest for a green lawn in summer seems attainable, and a lush garden makes its owner look and feel good. There are a few downsides, however.

When the weather turned hot a month ago, virtually every fungal and bacterial disease encouraged by warm, wet conditions made an appearance.

There's fire blight on apples and pears, including the Bradford and other ornamental varieties of the callery pear. This bacterium produces dieback in stems and leaves, yielding a classic shepherd's crook at the stem end and a blackening as if the branch had been burned. Experts have come up with a clever way of pruning out the dead branches in a way that stops the disease from forming in lower branches. It's a two-step process that initially leaves a stub. See the Maryland Home and Garden Information Center Web site, http://www.hgic.umd.edu.

I'd say that black spot in roses is becoming a problem, but only in roses that still have their leaves. Weather-induced or not, in May and June there was an outbreak of rose slugs the likes of which have rarely been seen. The pest, which is the larvae of a sawfly, munches on the underside of rose leaflets until it chews right through. "More [damage] than I have ever seen in all the years I've been doing this," said David Yost, a horticulturist at Merrifield Garden Center, who runs a diagnostic plant clinic for customers. He also reports unusual numbers of bagworms and wonders if the mild winter is a factor.

But the drumbeat is more of foliage problems. This has been a banner year for leaf spot on redtip photinia as well as anthracnose disease on sycamore leaves. The black-eyed Susans in my garden are robust, but the lower leaves are heavily marked by a fungus named Septoria. I sometimes remember to spray them in May with a lime-sulfur fungicide (this prevents the disease from gaining hold), but I didn't this year. Must have been singing in the rain.

My tomato vines are just showing signs of early blight, a disease that turns the lower leaves black and yellow. Mulching the bed will help, as will removing the infected leaves and avoiding overhead watering.

As Yost points out, most of these diseases are not going kill their hosts and are part and parcel of a rainy year. However, perennials and herbs that favor free-draining soil, typically those with silver or gray leaves, will croak in wet clay soil, from root or crown rot. Heavy organic mulches increase the risk.

Another problem, if it is a problem, is the sheer amount and weight of fruit and flowers on shrubs and trees. Peach tree boughs are groaning in spite of repeated thinnings of developing fruit, said Matt Davenport, manager of Hollin Farms in Delaplane, Va. Cherry trees are similarly fruitful, the corn is "phenomenal," he said, and the hay meadows produced two to three times the normal amount in May and June. His crews are getting ready to cut a second crop of hay in late July, a resource unavailable in last year's drought.

This bounty is seen, too, in ornamental plants. Trees that might grow a foot a year have doubled their fresh growth. In my garden, I've spent the last month thinning tree and shrub canopies and cutting back some perennials that have bloomed. A bank of fig trees, big shrubs really, have filled out wonderfully at the base of a red oak tree. The climbing hydrangea is now half covering the window of my second-story bathroom. A pair of plant pots, left in April at the edge of an embankment, are now partially engulfed by a burgeoning ground cover, leadwort.

Weeds are having a ball, and anyone who has neglected to weed on a weekly basis can expect to see pokeweed approaching shrub size.

There is another price for all this abundant moisture: the explosion in mosquito populations.

"They're breeding in a lot of places, going by trap counts and what my larviciders are telling me when they're running out of the woods," said Jeannine Dorothy of the Maryland Department of Agriculture. Larviciders have the unenviable job of going to wet breeding grounds to spray the mosquito larvae.

The presence of vernal pools (temporary woodland ponds) has created "a tremendous early-season problem," she said. "Probably at least 60 to 70 percent more mosquitoes" than usual.

Reducing mosquito populations means policing the yard to find and remove any source of standing water, which is easier said than done. Even corrugated drainage pipes can hold, in their interior indentations, enough water for the pervasive Asian tiger mosquito to breed.

This recent import, as we all know, defies native mosquito behavior by being active in broad daylight.

The key is to eliminate the waterborne larvae before they become blood-sucking flyers, said Jorge Arias, of the Fairfax County Health Department. But if your property is overwhelmed by the adult insects, you can spray an insecticide called permethrin labeled for use against mosquitoes. This pesticide is toxic to fish and beneficial insects, so follow the label directions carefully.

Arias pointed out that mosquito problems are made worse in neighborhoods with unoccupied homes in foreclosure. "With people not living there, they don't take care of where the water is accumulating," he said.

So you can imagine my relief when a public relations person named Dustin called out of the blue to tell me about a new product that has outdoor enthusiasts "raving about the head-to-toe protection they get" from the "Don't Bite Me! Patch." This is applied like a nicotine patch, except it infuses your bloodstream with Vitamin B1and aloe, and then you give off an odor that is offensive to mosquitoes.

"I don't think it's going to protect you that much," Arias said when I told him about it. I followed the instructions to the letter and stepped into the garden at 7 p.m., prime time for mozzies. By the time I had dunked a watering can in the fish pond and delivered it to a wilting hydrangea, an Asian tiger was on my index finger probing with her needle. I went over to the veggie garden, where I was unable to offend three more hungry tigers.

Ah, well, back to lemon eucalyptus spray.

Even with the pests, this is a good year in the garden. Last year, the drought withered not just the plants but the gardener's heart. This year's lushness has given us a redeeming paradise.

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