Q. What insect or disease would cause the flower stalks of my beautiful delphiniums to become twisted and their flower buds to curl and blacken?
A. The cyclamen mite is a damaging pest of indoor greenhouse plants such as African violets and begonias, as well as outdoor annuals and perennials including snapdragons, geraniums, ivy and delphiniums. The microscopic mite lays eggs in moist, dark places, and the developing young larvae feed on plant and flower tissue, creating the damage you have described. Stems can thicken and twist into deformed shapes while the flower buds often contort, blacken and fail to open.
Early detection is the key to preventing the spread of this mite to nearby susceptible plants. Because mites are impossible to detect without a microscope, they can easily spread on contaminated clothing, gloves and other gardening tools. Remove and discard all infected plants from the garden. Do not plant susceptible varieties in the same garden space since adults overwinter in the soil. Approved miticides have limited success. Take care to buy healthy transplants and isolate any houseplants that appear infected.