Plant Diseases/Dahlia disease??
HEELPPPP. Last year I planted some dahlia tubers and they sprouted and grew flowers that were really ugly and deformed. They survived the winter, and have sprouted and again, the flowers are deformed, and within 24 hours the flowers turn to a ball of black goo. Why is this happening?? Photos are on my facebook, links below
There are two good possibilities that may be responsible. There may be a tiny insect called thrips that are within the flower - often before it ever open completely. Very tiny, fast moving little critters that get down deep in the bloom. Slowly and carefully separate the petals of a young bloom to look for these "flea sized" insects. They can deform/destroy blooms. Another more remote possibility is a fungus disease called flower blight caused by the fungus Botrytis. It will often attack flowers first. You can recognize the fungus on the bloom by the appearance of a gray "fuzzy" covering on the affected petals.
If you are still stumped, you may consider showing a few of these blooms to your local garden center/nursery for their comments OR contacting your local county Agricultural Extension Service- often located in the county courthouse bldg. There are a couple of labs in Alabama that can diagnose these types of issues. They are operated by the Extension Service and are located in Birmingham at the botanical garden and one at the Auburn campus.