Answer: Balled asparagus foliage is a sign of the asparagus aphid. The pest overwinters as small, black eggs on dead asparagus stalks and foliage. In spring, when new stalks begin to emerge from the ground, the eggs hatch and the young begin feeding exclusively on the stalks and young volunteer asparagus seedings. During feeding the aphid injects a substance that causes the asparagus foliage to grow into balls, and heavy infestations can reduce production. The aphids feed until fall, when they mate and lay eggs.
To control the aphids, remove asparagus foliage after it dies in the fall. This reduces the number of overwintering eggs. Weeding your patch of the small volunteers, which young aphids feed on first in spring, will also reduce the damage. For heavy infestations, spray insecticidal soap when the spears begin to send out branches and the fernlike leaves. Repeat the spraying a few times during the growing season, whenever you notice damage to the leaves.
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