Black Nightshade is a common weed species in a varieties of regions. The Hairy Nightshade growing degree day model uses heat units and time as a method to estimate plant phenological stages through the growing season. This can be helpful to time herbicide applications before berry and seed production occurs.

Calculating Growing Degree Days

For this model, a lower temperature threshold of 6C is used to calculate growing degree day accumulation beginning when the first cotyledon/ plant emergence is observed. Growing degree days can be calculated from daily high and low temperatures, or via the Pest Prophet app, which uses hourly temperature data for a given field. The first flower will occur at 600 GDD (C) with average viable seed at 1000 GDD (C).

Learn More:

McGiffen, M. E., Jr. and J. B. Masiunas. 1992. Prediction of black and eastern black nightshade (Solanum nigrum and S. ptycanthum) growth using degree-days. Weed Science 40: 86-89.