One of the things I like best about writing this column is that if I have a question about what to do in my own garden, I figure other people are having the same questions and I should write a column.

That means I can call any expert in the state for answers.

While winter moths are visible in early winter their damage is done in the spring, when the eggs they lay on tree trunks hatch. maine.gov photo

My wife Nancy and I have not harvested more than a half-cup of blueberries since our neighbor’s Norway maples shaded and out-competed our six highbush blueberry bushes about a decade ago.

After we planted a few blueberry bushes in sunnier spots in our yard, the winter moth arrived in our coastal area, with the moth’s caterpillar stage eating all the blueberry blossoms and eliminating any chance of fruit.

This year we are getting serious. We have a strip of land, about 8 by 40 feet, where a neighbor couple has grown vegetables for 15 years or so. Last fall they informed us they wouldn’t be using it anymore.

Nancy has ordered one each of the 10 highbush blueberry varieties Fedco is selling, and they will arrive in early April. Seven of the 10 – Bluecrop, Bluray, Jersey, Meader, Nelson, Patriot and St. Cloud – are on the University of Maine Cooperative Extension list of recommended varieties in its pamphlet on growing highbush blueberries, so I think we and Fedco picked well. You have to plant at least two varieties for cross-pollination.

The publication did not mention winter moth, so I called its author, David Handley, who is based at Highmoor Farm in Monmouth.

Handley said winter moth is worrisome because it could spread throughout the state, beyond the coastal areas where it is already a problem. But he believes we should be able to control it.

If you aren’t sure you have winter moth, go out in early spring as the buds begin to swell, bring a good magnifying lens, and check for eggs or damage on the branches near the buds. If you find either, spray with horticultural oil. If you have had winter moth in the past, spray anyway.

“That’s the same treatment growers use regularly for mites, scale and other sucking insects,” Handley said. “The oil coats the eggs and suffocates them.”

Before you call me or email my editor: horticultural oil is a very fine oil designed to smother the eggs some pest left on your bush or tree. This involves no chemicals other than the oil.

In Monmouth the time to spray is usually late March, Handley said.

I wondered if, being farther south and with the weirdly warm winter, we should spray earlier – even when I called him in late February. He advised me to check, but it was probably too early. I did check and he was right – but I will be checking again and probably spraying in early March when this column appears.

He emphasized that you should not use horticultural oil – also called dormant oil – once the leaves have begun to come out.

If the oil does not work in killing the eggs, a backup plan is to apply the organic caterpillar killer Bacillus thuringiensis, commonly called Bt. If you see caterpillars as soon as the buds begin to unfurl, spray.

“This spray puts out a protein that rips out the guts inside the insect,” Handley said. “The one thing is that you have to spray when the caterpillars are very, very small” for it to work – so use a hand lens and look regularly for the pests. The spray is harmless to mammals, including people.

Even if the winter moth did not exist, people make a lot of mistakes growing highbush blueberries, Handley warned.

Highbush blueberries are native to Maine even though the state is better known for its lowbush varieties. Highbush plants usually are found at the edge of lakes, and people mistakenly believe they need damp soil. They don’t.

“When they grow wild, the roots are not in the water – at least during the growing season,” Handley said.

What they prefer is acidic sandy loam soil with a pH in the range of 4.5 to 5.2 and rich in organic matter. Blueberries will not grow in clay, Handley advised. Most Maine soil is acidic so, unless people have been adding lime to the soil, it should be OK. If the soil is not acid enough, add sulphur or aluminum sulfate. Nancy and I are planning to add compost and till it in deeply to the section where we are planting the blueberries because if all goes well these bushes will be in that location for the next 25 years.

Handley said many people make the mistake of digging a 1-foot diameter circle in their lawn and sticking the blueberries there. It won’t work.

“The lawn grass will come out with a vengeance in the same spot and compete for same water and nutrients, and it’s the grass who will win that battle,” he said. If planting in a lawn “clear the whole area at least 4 feet square and mulch heavily.”

Handley had some advice that I did not want to hear, but I will follow.

Even with the 1-year-old plants we are getting from Fedco – the Extension pamphlet recommends 2- or 3-year old plants – the plants will produce blossoms and try to produce berries the first year. You should gently rub those blossoms off so all of the energy goes toward the roots.

Oh, well. I guess we’ve been without blueberries for several years, we can wait another year. Unless I miss a few of the blossoms when I’m removing the blossoms.

Tom Atwell is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at tomatwell@me.com.

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