What is the black substance on Poppies that is causing the stem to rot?
What is the black “gunk” on the stems of my Poppies that is rotting the stem and causing them to snap off below the blossom? This has never happened before. The plant had 33 pods and just prior to blossoming, this gunk started to appear and several of the stems rotted through prior to blossom. This has also occurred after blossoming, causing the flower to rot off the stem.
Lynne M. Holland, Horticulture and Social Media Professional
We know poppy sap is like a white latex. It also blackens quite quickly. It is possible that it might be an insect biting the stem and then leaving a hole where the sap then oozes out. A likely suspect would be snails or slugs. It is best to see these at night so a walk through the garden with a flashlight might “illuminate” the problem. Our entomologist is not aware of poppy-specific borers so that is unlikely.
It might also be environmental if the poppies are being buffeted by wind or impacted by traffic (animal traffic) that is causing damage to the stem. Has anything changed in the surrounding area that might be physically damaging the plants?
It is possible it is a symptom of a disease. You can send a sample to our diagnostic lab by following directions on this page: https://extension.umaine.edu/diagnostic-lab/submit-sample/ They need a live sample so they can grow out any suspected pathogens.