The Emerald Ash Borer is a wood-boring moth that mostly affects ash trees. It is widespread in the United States and has caused millions of tree deaths.

Emerald Ash Borer Life Cycle Stages

Emerald Ash Borers usually take one or two year to complete a generation. Emerald Ash Borers overwinter as larvae in the tree, and resume feeding activities spring or late winter. These larvae then pupate and adults emerge in late spring or early summer. Adults then feed and reproduce.

The period of adult emergence is key for insect prevention, both for placing traps and for using insecticides, if necessary. Researchers have created the Emerald Ash Borer Adult Emergence Growing Degree Day Model to better predict when the adults will emerge.

Calculating Growing Degree Day Units

The Emerald Ash Borer Emergence Growing Degree Day model uses a lower threshold of 50F and an upper threshold of 100F. It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field.

Using Jan. 1st as a default “biofix” date, or starting point for accumulation, the first adult emergence occurs at approximately 550GDD (F) and peak at approximately 856 GDD (F). This can be used to guide pest management decisions and timing.

Source:

Duarte, Samuel Andres Discua, 2013. Characterizing Prepual Diapause and Adult Emergence Phenology of Emerald Ash Borer. The Ohio State University.