Answer: Is the asparagus bed getting enough moisture? They are very thirsty plants. On the other hand, they need a well-drained soil, and will decline if planted in a low-lying area where moisture accumulates. Otherwise, check for signs of aphids or mites on the fronds, and if you find them, use insecticidal soap or a hard blast of water from your garden hose to do them in. Check frequently and reapply control measures if the pests reappear. To help your plants recover, do not harvest any spears next spring, and judge whether or not to harvest the following year based on the plant's performance next year.
The only other thing I can think of is Verticillium wilt - I'm not sure if Jersy Knight is resistant, but Mary Washington is not. Unfortunately, if there's verticillium in the soil, there's nothing you can do to save your asparagus from decline and death. You'll have to put new plants in an area where no verticillium-succeptible plants (tomato, potato, pepper, and many ornamentals, etc.) have been grown in the last 3 years. You can call the county agricultural extension office (ph# 502/425-4482) to find out for sure if the problem is verticillium (they may ask you to send a plant sample to their testing lab). I hope it's not wilt, and wish you the best of luck!
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