AROUND THE GARDEN

Gardens have two types of invaders beyond the 2- or 4-legged ones. Last week, I wrote about plants, introduced and accidental, which, having few enemies, replace more desirable plants.

This week, the Emerald Ash Borer is on my mind – not because it’s in my garden, but because a trap for it is. You may have seen these Barney-hued devices popping up here and there, hanging twenty or more feet up in an ash tree.

Resembling alien invaders themselves, the traps serve an important purpose. The Emerald Ash Borer, or EAB, has been in the U.S. at least since 2002, when it was discovered in Michigan. Like many dangerous insects, it probably arrived from China in wooden pallets.

So far, the EAB has wreaked havoc in Michigan, and has been found in 15 states, as well as Canada. The most recent find was in upstate New York, twenty-five miles from the Connecticut border.

Ash trees were planted, often as a monoculture, as street trees in the Midwest after the demise of the American elm. Monoculture planting was a major cause of the loss of elm trees to Dutch elm disease. Now a similar fate has befallen the ash, and the insect has spread into the forests. At least seven million ash trees were killed in Michigan.

In our area, ash trees have been in decline for years – in fact, a cluster of ash problems is referred to as Ash Decline. Ashes also suffer from Ash Yellows, a Mycoplasmalike organism, or MLO, which clogs up their phloem.

Adding the EAB to the mix will mean that at least one tree in twenty in our state is under attack. In some neighborhoods, many street trees will die.

A small greenish beetle, the EAB, in its adult stage, merely nibbles on leaves. But after feeding, it must procreate, and it does so by penetrating the bark of the tree, laying its eggs in the cambium, where all water and nutrients travel. After hatching, the larvae graze through the cambium, clogging up the works as they go. Eventually, the larvae bore out through the bark, leaving small, D-shaped holes as they go. The insects are so small, (as are the exit holes), that a tree can be in serious distress before the insect is found.

Chemicals are available as a preventive for this insect, but clearly, not applicable for forest trees. A key step in preventing the spread of the EAB is to avoid moving firewood across state lines. Equally important, but apparently not obvious, is to not ship ash trees across state lines – Maryland became infested because of a dim-witted nurseryman in Kentucky.

Sightings of the EAB must be reported immediately to the CT Agricultural Experiment Station, 203-974-8440. My trap will be inspected later this year by a team of researchers from the UConn Extension. I will report any findings here.