Magnolia scale on banana shrub – control

Q: I’ve got cooties on a banana shrub. Leaves have black soot on them. Limbs have brown growths. Thoughts?

A: Your banana shrub has magnolia scale. These insects suck sap and then excrete a sticky liquid called honeydew. The honeydew coats nearby leaves and a dark fungus called sooty mold grows on it.

Control comes in three steps: first, spray the stems with neem oil. This will suffocate some of the adults. Next, use a systemic insecticide that contains imidacloprid (click for sources) after flowering. This will kill more of the adults. Third, spray neem oil on all stems on July 1 and Aug 1. This will kill many of the young crawlers that emerge from the adult female covering in late summer.

The round bumps won’t fall off even if the creature inside is dead. You can pop them off with the tip of a knife if you are bored and need something to do while social distancing.