Furry carrots? Twisted roots? It might be aster yellow phytoplasma!
The bacteria that cause this disease reproduce in leafhoppers, root knot nematodes, and in the phloem of susceptible plants. These bacteria help leafhoppers and nematodes to live longer, but in our plants, the opposite it true. As bacterial populations grow, they block the flow of sap, water, plant hormones, and nutrients within our plants, causing chlorosis (yellowing) and distortion.
There is no known cure for aster yellows, so we have to look at the disease vectors: leafhoppers and root knot nematodes. Since leafhoppers can overwinter in weeds and perennial ornamentals, such as thistle, dandelion, black-eyed Susan, and wild carrot, keep these plants trimmed back from carrot planting areas. It’s probably a good idea to plant your beets somewhere else, too, since beet leafhoppers can be carriers. Bacillus thuringiensis (Bt) can be used to control these disease carriers. If an area becomes infected, avoid planting carrots there for a couple of seasons. Severe infestations can be dealt with using soil solarization, but that’s pretty drastic, since it kills everything in the soil, including beneficial soil microbes.
If you have deformed carrots, let’s just hope that is is caused by rocks or compacted soil, as those problems are much easier to fix. And, hey, those carrots can look pretty amazing!
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.