OPUS: Understanding How Climate Change Will Alter the Ability of Pathogens to Control Gypsy Moth Populations, and the Consequences for Forest Economics

When they think of infectious diseases, most people think of diseases like covid-19 or HIV that have big negative effects on people and the economy. Few are aware that infectious diseases also keep pest insects in check, by killing insects before they can destroy forests. The gypsy moth is a classic example.

Gypsy moth populations are held in check by a fungus disease that can kill more than 90% of gypsy moth caterpillars in a single spring. Since the fungus disease was introduced in 1989, gypsy moth defoliation has been very low, reducing the costs of gypsy moth attacks by millions of dollars every year. The fungus needs cool, moist conditions, however, and so the hotter, drier conditions that climate change is bringing to the US may lead to a gypsy moth comeback.

Before the fungus was introduced, a virus disease killed many gypsy moths, but whether the virus can control gypsy moths in the future is unknown. This project asks, what will be the economic costs of a gypsy comeback, and can a virus comeback reduce these costs? Results will be presented to forest managers for input and refinement, and will be used to inform management decisions.

Additionally, a graduate student and a technician will be trained in population and economic modeling.

To answer these questions, the researchers will use a combination of ecological field experiments, infectious disease modeling, and economic modeling. They will use field experiments to estimate key parameters of their disease model, notably the severity of competition between the virus and the fungus, and how this competition depends on weather. The researchers will then extend their disease model to describe long-term virus-fungus competition, and the extent to which the virus can replace the fungus as climate change leads to hotter and drier climates.

To understand the economic consequences of virus-fungus competition, the researchers will first parameterize regression models that quantify the economic costs of gypsy moth defoliation. They will then insert the predictions of climate change models into their virus-fungus competition models to predict how climate change will affect gypsy moth defoliation.

The final step will be to quantify the costs of climate change on gypsy moths by inserting the model predictions of defoliation levels into the economic models. This work will provide a rare quantification of the effects of climate change on a species interaction, and of the economic costs of such effects.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.