Given the ever-increasing world population, maize plays a pivotal role in global food security. A major obstacle facing farmers is stalk lodging (the breakage of the stalk before harvest), which leads to losses in annual yield. Disease and pest damage in maize stalks are some of the major causes of stalk lodging. This research aims to develop and validate methods to non-destructively determine the transverse stiffness of maize stalks, which is highly related to the presence of disease and pest damage. A handheld device for determining the transverse stiffness of maize stalks in the field has been developed. It is a single-user non-destructive device and has an operational battery life of up to 6 hours. The device enables high-throughput phenotyping of live plants and quick identification of individuals affected by diseases (such as stalk rot) and pest damage. Finite element models were also generated to investigate the effects of pest damage and disease on transverse stiffness. Specimen specific models were generated using geometric information obtained from CT scans of maize stems. The models were loaded in transverse compression and the effects of pith voids and or reduced pith integrity (e.g., degraded material properties) were investigated directly. Experiments were conducted to validate results from the device and the finite element analysis models. The device provides farmers a quick, easy, and reliable method to measure transverse stiffness and detect disease or pest-damaged plants in the field. The finite element models will enable scientists to determine the physiological factors that affect transverse stiffness in maize stalks. This research will ultimately lead to lower stalk lodging and higher yields in the future.