This fungus is a member of the ascomycote family and affects many types of plants. The name “ascochyta blight” refers specifically to a type that affects stems, especially of asparagus, but is close enough in taxonomy to other asochyta types that it can also refer to others that affect similar plants.
Ascochyta blight can affect a number of hosts including various beans (garbanzo, chickpea, lentils, etc.), grasses including Kentucky bluegrass and many grains, and stem plants such as asparagus. It can also affect flowering plants such as lilacs.
As with most blights, ascochyta manifests first as small spots on leaves or stems. These irregularly-shaped blotches start out small and grow quickly, covering leaves, pods, stems, etc. They are dark brown or black in color and if left to their own devices, will infect the entire plant until it literally crumbles from rot.
The lifecycle of this fungus is similar to most others. It most often infects plants by first having infested the seeds or seedlings that are then brought to the garden. The fungus does not begin spreading until the weather is quite warm and then spreads very quickly and can infest an entire garden in a matter of days. Other than seeds, it can spread through infected soil, compost that has not been properly made, and some mulch.
It thrives in wet and soggy conditions when the ambient temperature stays warm and the conditions damp.
How Ascochtya Impacts the Plant
It often kills or severely stunts garden plants and can do so relatively quickly – within a couple of weeks of its manifestation. It can be “dormant” during cooler temperatures and underground and its spores can survive for some time away from a host. It especially enjoys overhead and long-term irrigation (such as long periods of rain).
Plants that are infected will often not bear fruit or bear only marginal starts before succumbing to the fungus.
How to Prevent Plant Fungus
As with most fungi, prevention is all about proper irrigation, plant spacing (for aeration), and care. Rotation of crops can help and turning the soil or using only high-quality inputs will keep this from spreading. Diseased plants should never be composted.
Treatment can be done in a variety of ways, but must be done quickly. Sprays and powders to kill the fungus are common and work well. Prevention is the best method, of course, but once it manifests, it should be dealt with very quickly.
Natural treatments include a few enzyme sprays and just letting the plants go into a “mini drought” with no water for several days. These have varying results.