The problem of simply and reliably estimating starch content of cassava roots in the field has been addressed with the development of a low cost test instrument based on the measurement of return loss at radio frequencies. A clear relationship between starch content of cassava tubers and the measured return loss of tuber samples at a specific frequency of 30MHz was verified experimentally. A prototype test instrument was designed with goals of low cost and simplicity of use. The test instrument displays starch content in 5 categories, from ”low” to ”high” using an array of 5 LEDs. The performance of the test instrument was experimentally verified in the field and a reliable correlation between tuber starch content and LED indication was demonstrated.