CAPS Update: Gypsy Moth

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CAPS Update: Gypsy Moth

  A female Asian gypsy moth is shown on the left. Its large wings allow it to fly. The European gypsy moth female on the right is unable to fly.
  Gypsy moths lay large masses of eggs, primarily on trees. But sometimes eggs are laid on cars, trucks, or trailers, leading to possible spread to uninfested areas such as the western U.S.
  Feeding by gypsy moths can lead to complete defoliation of trees. Typically, trees refoliate, but when gypsy moths feed year after year, as seen in eastern forests, some trees cannot recover.

Two subspecies of gypsy moths are of concern to Utah and the entire United States, the European gypsy moth, Lymantria dispar, and the Asian gypsy moth, L. dispar asiatica. These two related moths are very similar, but the Asian gypsy moth has a broader host range. Also, Asian gypsy moth females are active fliers, while European gypsy moth females are flightless; therefore, Asian gypsy moths are more likely to spread quickly throughout the U.S.

The Asian gypsy moth was first found in the U. S. in Washington in 1991, allegedly from egg masses on ships traveling from eastern Russia. It has been found in North Carolina and Oregon as well. Several potential hosts for this pest are found in Utah, including oaks, willows, and several evergreens.

The European gypsy moth was originally introduced to the U.S. in 1869 by E. Leopold Trouvelot, who wanted to breed them as silk moths. Unfortunately, the moths escaped, and because they have no natural predators or pathogens in the U.S., they have been a troublesome defoliator in the East ever since. Utah’s oak and aspen trees are potentially threatened by this pest.

The Utah Department of Agriculture and Food monitors for both subspecies of gypsy moth. Populations of European gypsy moth have been found and eradicated twice in Utah. Thus far, Asian gypsy moth has not been detected in Utah.

Both of these moths are easily spread by travelers, and people are encouraged to be aware of them, especially when traveling from quarantine areas (click here for map) to non-quarantine areas. Also, it is important that firewood is not moved from one area to another. Always purchase firewood locally once you reach your destination. In fact, movement of firewood creates a huge risk for spreading many pests, prompting the creation of a dedicated website: Additionally, USDA APHIS has recently launched a new campaign aimed at educating people that are relocating to a new area about the possibility of spreading gypsy moth to their new homes. Information can be found at

-Cory Stanley, USU CAPS Coordinator  



CAPS (Cooperative Agricultural Pest Survey) is a federal program, administered jointly by USDA-APHIS-PPQ and each state, whose purpose is early detection of invasive species that could threaten U.S. agriculture. In Utah, the program is co-coordinated by Cory Stanley (USU) and Clint Burfitt (UDAF).