News from Elsewhere

Emerald ash borer (EAB)

The Agrilus species identified in Detroit earlier this year as Agrilus planipennis is creating quite a stir. Besides the fact that this is the fourth new beetle from China discovered in the US this year, and that ash is the bread-and-butter species for many communities plagued with other invasive pests, the size of this infestation and the number of trees it has killed after what appears to be a relatively short period of time is alarming.

While little is known about this beetle, here are some of the issues being discussed:

Although EAB has only been found on ash in Michigan, Asian references list Ulmus and Juglans spp. as other potential hosts. Because these references include several named pseudonyms, the taxonomy is not clear. If there are clear sub-species, they may have different hosts as well as survival strategies. That may be good or bad news for US forest resources.

Surveying is very difficult. So the current extent of infestation is not known. There are no known pheromones to use for monitoring. The beetles attack all age and size classes of ash. They can attack live and recently killed trees. They are strong fliers, over distances yet to be determined. Preliminary survey results suggest a million infested trees occur across something close to 1000 square miles. While agricultural fields may help isolate the infestation on some fronts, containing the population (assuming its boundaries can be defined) is going to be many times more difficult than containing the recent ALB infestations.

A number of cooperative groups are discussing management recommendations. These include Canadian as well as US partners, state, federal, and provincial. Eradication may not be feasible, but that possibility has not yet been ruled out. Successful eradication is more likely in Canada where the infestation is bounded by water on two sides and agricultural lands on the third (Detroit makes up the fourth side). In Michigan, a slow-the-spread (STS) approach is being discussed, but officials are a long way from making a final decision. If an approach similar to the gypsy moth program were implemented, it would likely consist of a series of buffers of varying widths, utilizing different management strategies in each. However, such an approach would require the boundaries be defined and state and federal authorities be given additional legal authority to manage uninfested trees on private lands. And of course the funds have to be found to fund a project many times larger than the ALB projects in Illinois and New York put together.

Emerald ash borer galleries and d-shaped exit holes.

The beetle can apparently kill trees in three to four years. While the length of time the infestation has been established is being debated (somewhere between five and ten years), that is a relatively short time. For those of us not familiar with entomology, here?s a frame of reference. Most new gypsy moth infestations (outside the generally infested area) are discovered within two to five years of establishment. At the time of discovery, most can be successfully treated because they are relatively small. If eradication is not successful, defoliation can be expected in five to fifteen years, with scattered mortality some three to four years after that. While the gypsy moth cannot be really compared to the EAB (in another insect order altogether), many are familiar with the effort and dollars spent in tracking the gypsy moth. They are also aware of some of the potential impacts, if the moth becomes established in Minnesota. EAB has ?gone from zero to 60" in a fraction of the time it would take the gypsy moth to produce any mortality at all, let alone hundreds of square miles.

However, until more information can be gathered, control in Michigan is on hold and all we can do here is educate ourselves, carefully monitor our forest resources and report suspected invasive pests to our local authorities. If you observe extensive ash decline, look for signs of borer activity. Report your finds to a local resource professional (MDA, MNDNR or UMN Extension agent).

A comparison of 20 commercial deer repellants

In the fall of l998 and the spring of l999, twenty commercial deer repellants were tested for their effectiveness by the Animal and Plant Station, USDA, in Olympia Washington. Tests were conducted in five pastures, each containing five or six captive black-tailed deer. Each pasture varied from two to five acres with natural habitat consisting of Douglas fir, alder and associated understory vegetation. Western red cedar seedlings were planted in 21 plots scattered evenly across each pasture. Seedlings were planted just before treatment with repellant. A separate plot was used for each repellant, with one plot of untreated seedlings serving as a control.

Cedar seedlings were examined for browse damage at 24 hours, 48 hours, and l week after planting, and then at 1-week intervals for l8 weeks. Damage was determined by counting numbers of bites taken from each seedling. Seedlings pulled from the ground were considered destroyed and recorded as having 25 bites, and no more than 25 bites were recorded because seedlings were generally defoliated by then. See table below for the results of the winter test.

A copy of this deer repellant study, which includes more information that in this article, can be obtained by writing to Andy Trent, Project Leader, USDA, Forest Service, MTDC, Bldg. 1, Fort Missoula, Missoula MT 59804-7294; phone 406-329-3912; Fax 406-329-3719; or E-mail: atrent@fs.fed.us.

Results of winter 1999 test of 20 deer repellants.

Larger version of this graph.