A large theoretical literature in sociology connects increases in incarceration to contractions in the demand for labor. But previous research on how the labor market affects incarceration is often functionalist and seldom causal. We estimate the effect of a shock to the southern agricultural labor market during a time when planters exerted a clear influence over whether defendants were incarcerated. From 1915 to 1920, a beetle called the boll weevil spread across the state of Georgia, causing cotton yields and the share of farms worked by sharecroppers and tenant farmers to fall. Using archival records of incarceration in Georgia, we find that the boll weevil infestation increased the black prison admission rate for property crimes by more than a third. The infestation’s effects on whites and on prison admissions for homicide were much smaller and not statistically significant. These results highlight the importance of studying incarceration in relation to agricultural as well as industrial labor markets and in relation to sharecropping and tenant farming as well as slavery.