Spongy moth (Lymantria dispar) populations go through dramatic changes in abundance over time. Most of the time, populations are relatively low and caterpillars can easily go unnoticed. However, under the right conditions (e.g., favorable weather), populations can increase at a rapid rate and lead to an outbreak. It’s during this “outbreak” stage that we have problems with spongy moth. It often takes one to three years before starvation, disease, and natural enemies (predators and parasites) cause the population to crash to low levels, but significant defoliation can occur during an outbreak.