Gypsy moth certification for spruce, fir and Douglas-fir

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Firms that ship trees and shrubs out of Michigan must have the stock certified for the USDA gypsy moth quarantine if it is shipped to non-infested areas. Many types of trees and shrubs can be approved through a visual inspection by the Michigan Department of Agriculture (MDA). The exception is spruce, fir and Douglas-fir trees, which are considered high risk for harboring gypsy moth. These species get a high risk rating because of two factors: 1) they are known hosts of gypsy moth; and, 2) the branches and needles are so dense that it is almost impossible to find 100 percent of the egg masses laid in the tree. Therefore, MDA uses what is referred to as a systems approach in its certification program as the basis for assuring the trees are free from gypsy moth.

The MDA program requires at least one treatment for gypsy moth and an inspection by MDA before a certificate can be issued. The treatment must be properly timed so that it is effective. The time period is described as a spray window. The window corresponds to the period of egg hatch through late instars. Growers may choose from over a dozen compounds which have been approved by USDA for gypsy moth. A list of compounds approved for 2008 is posted on the MDA web site:

In these early weeks of spring, firms often start shipping balled and burlapped stock as soon as they can start digging. This is permissible for stock previously treated up to the point when hatch occurs. Once gypsy eggs begin hatching, the certification clock is reset. At that point, a new treatment is required along with a new inspection. MDA advises that out of state shippers discuss shipping requirements early with their district inspector. Additional certification requirements for Japanese beetle and noxious weeds may apply when shipping spruce, fir and Douglas-fir as live nursery stock.

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