Island Spruce Trees Suffer Severe Damage
By JOSHUA SABATINI
An insect species never before recorded on Martha's Vineyard has attacked spruce trees Islandwide, damaging many and even killing a few, say area scientists and tree experts.
The pest was identified this month as a Spruce aphid (elatobium abietinum) by a cooperative effort of scientists at the University of Massachusetts.
The generally wingless creatures are 1.0 to 1.5 millimeters in size and have a greenish color resembling that of needles on Island spruces; a head with a lighter green hue than the rest of the body, and red eyes.
The insects, described by scientists as having "piercing, sucking mouth parts," line up on the tree's needles and draw out nutrients. The insect's life cycle from January into early June, meaning that for spruces on-Island, any damage this year has already occurred.
One of the Islanders who first spotted the insect in May is Richard Manley, a certified arborist and owner for more than 40 years of Manley Tree Service in Vineyard Haven.
Beginning in early May, Mr. Manley said, he saw something he never had before. Distressed trees that appeared to have a rust disease at first glance turned out, upon further examination, to have limbs loaded with insects.
Mr. Manley said he personally saw more than 200 spruce trees affected by the insect, from Chappaquiddick to up-Island.
Other landscapers, nurseries and tree owners on the Vineyard shared his concerns.
John Varkonda, supervisor of the 5,200-acre Manuel F. Correllus State Forest, said he has noticed unusual damage to the spruces in the forest, but nothing life-threatening. He said he has also observed spruce damage elsewhere on the Island, just by driving around.
Mr. Manley took samples of the trees to Roberta Clark, a horticulturalist at the UMass extension in Barnstable. Believing the insect was a Spruce aphid, Ms. Clark contacted Robert Childs, a UMass entomologist, who confirmed that the culprit was indeed the Spruce aphid.
In late May, Mr. Childs said, he received many reports that the needles of spruce trees on the Vineyard landscape and in nurseries were turning brown and eventually shed by the tree.
The aphid is capable of "causing severe injury, to the point of death," he said.
According to an alert drafted this month by Mr. Childs and Ms. Clark, potential hosts for the aphid are all spruce species (Picea) that are found in the Northeast landscape, nursery and Christmas tree plantations. The pest "is being commonly found now on white spruce (P. glauca), Norway spruce (P. abies) and blue spruce (P. pungens)."
The first observations of this insect damage in the Northeast are not isolated to Martha's Vineyard. Similar reports have come in this year from Cape Cod and Rhode Island, particularly Block Island - although Mr. Childs said the Vineyard has had one of the biggest outbreaks.
"It is not known when and how this pest arrived on Cape Cod, Rhode Island and Martha's Vineyard," the two authors wrote. "Most likely, it has been in these locations, in low numbers, and unnoticed, for many years."
While not knowing for certain how the aphid was introduced to the Island, Mr. Childs believes it was transported over on some plant material, perhaps a Christmas tree.
The two authors state that aphid outbreaks come in drought years that are followed by mild and dry winters.
"This is certainly the case for the affected areas in Massachusetts and Rhode Island," according to the alert. "These coastal areas generally have milder climates that are moderated by the ocean.
"No reports of this pest have been received inland from the shore areas of Massachusetts," the authors continue. "It has not even been reported from the South or North shore areas of Boston."
Mr. Childs said the mildness of last winter is most likely the cause of the outbreak.
Spruce aphids feed on the older needles of spruces first, starting usually at the lower branches and then making their way upward. Affected needles turn brown in late May and eventually drop off the branches.
"In the worst case scenario, the tree's only remaining needles may be those at the branch tips. Such trees will be left in a state of great stress and most likely will die," the alert says.
Conifers, the two authors write, are most impacted by the defoliation. This tree species is "unable to replenish multiple years of needle growth in one growing season."
Aphids are extremely active from January until early June, when they disappear until the following January.
When January rolls around again, no one is certain whether the aphid will make another dramatic appearance. Mr. Childs said an annual outbreak "could be devastating."
To test for the aphid next year, the two authors recommend that concerned tree owners shake a tree branch while holding a white piece of paper under it. If there are aphids in the tree, they will appear on the paper.
If the insects are spotted next year, there are ways of killing them and saving the tree. The two authors recommend a variety of methods: horticultural oil sprays, insecticidal soap and imidacloprid. The latter, though, is not allowed on much of New York's Long Island because of the sandy soils, a soil type similar to the Vineyard's.
For the infected trees Mr. Manley found in May, he said spraying them with his choice of pest control did the trick.
With the damage already done this season, and the insects no longer around, Mr. Manley said the only thing that can be done to restore the tree is to attempt to stimulate growth using fertilizers.
But Ms. Clark said the trees with insect damage this season may not survive the years to come.
Scientists are at a loss for preventing or managing an outbreak next year. The two authors do not know how the insect spends its dormant period, summer through fall, or in what form - a nymph, adult or egg.
The scientists have not discovered where the insects go during the dormant period, whether it is on the host plant or not. "These factors," said the two authors, "help to determine the development of a sound management strategy."
The Spruce aphid was first reported in the southwestern U.S. in the late 1980s, on the Fort Apache Indian Reservation located in the White Mountains of Arizona, according to a report last year by the Northern Arizona University School of Forestry.
Study of Spruce aphids in this region is ongoing.