Fusarium crown and root rot means death for asparagus.
Heavy soil, poor drainage, over-harvesting, and insect feeding all work to create the perfect habitat for this ubiquitous fungi.
Fusarium is a large fungal family that causes several different disease in many garden plants. You may have already heard of Fusarium wilt, but there are several different crown and root diseases caused by these pathogens. One version attacks pumpkins, melons, and other cucurbits. Another group of Fusarium fungi attack asparagus.
Rather than having a single cause, there are three different forms of the Fusarium fungi that cause this fungal disease of asparagus. This trio of Bad Guys go by the names Fusarium oxysporum f. sp. asparagi, F. verticilliodes, and F. proliferatum. [Don’t worry, there won’t be a quiz.] All three fungi colonize the roots and crown, and the first one listed can also infect xylem tissue.
Symptoms of Fusarium crown and root rot
Asparagus plants infected with the Fusarium fungi decline over time. At first, you may see one or more stunted, bright yellow ferns. This bright yellow coloration is a warning flag that should not be ignored. Wilting is also common. If you look at the crown area, you will see reddish brown discoloration. At this point, it is a good idea to pull the plant up, for closer inspection.
Cut open the crown or below ground area of the plant, to see if sunken brown lesions or reddish flecks are present. Then, look closely at the roots. Infected plants will have reddish brown, elliptical lesions on the storage roots. Feeder roots will probably rotted off completely, though any remaining tendrils will have the same reddish brown discoloration seen elsewhere.
Unfortunately, these fungi can survive in the soil indefinitely, and they are found pretty much everywhere. The disease is often spread as infected soil is moved from place to place on shoes, tools, and equipment. It can also be carried on seeds, which is why choosing reliable seed sources is so important. This disease can occur anywhere underground. Very often, insect feeding creates points of entry for these fungi. Asparagus miners are a common culprit.
Controlling Fusarium crown and root rot
Environmental conditions that keep plants healthy also improve their ability to prevent these fungi from entering in the first place, so avoid water stress and feed plants regularly with top dressings of aged compost. [Asparagus plants are very heavy feeders.]
Once a plant becomes infected, it should be removed completely, along with nearby soil, and disposed of in the trash. To reduce the chances of the disease taking hold in the first place, your asparagus plants should be rotated every five years and be sure to provide proper drainage.
Remember, perennial asparagus can provide you with many years of delicious spring and autumn spears, so don’t let these pathogens stop you from trying to grow your own!
You can grow a surprising amount of food in your own yard. Ask me how!