Declines in overwintering eastern migratory monarch butterfly (Danaus plexippus L.), have been attributed to the loss of common milkweed host plants from annual crop fields in the US Midwest. Currently, milkweeds in this region primarily occur in perennial grasslands, where disturbance is infrequent, predatory arthropods are abundant, and seasonal patterns of milkweed phenology differ from crop fields. We evaluated the potential for strategically timed disturbance treatments to enhance monarch butterfly oviposition and survival in common milkweed patches growing in perennial grasslands. One-third of each patch was left undisturbed, while the remaining thirds were mowed in either mid-June or mid-July, respectively, and allowed to regenerate. We subsequently measured effects on monarch oviposition, predator abundance, and survival of sentinel eggs and larvae. Monarchs laid more eggs on regenerating versus undisturbed stems under both mowing regimes. Predators were strongly suppressed by mowing treatments and survival of monarch eggs and early instars doubled in disturbed patches. Future work should focus on testing grassland disturbance as a management tool to improve productivity of existing monarch breeding habitat.
