Comfrey
A ring of comfrey under the branches shades soil, holds moisture, and crowds out the grass that competes hardest with young pear roots. Its deep taproot draws minerals from below the tree's feeding zone, and the leaves can be cut two or three times a season and laid down as mulch. Keep crowns a foot back from the trunk.
Yarrow
Yarrow's flat flower heads are among the easiest nectar sources for hoverflies, lacewings, and the tiny parasitic wasps that work over pear psylla and aphids. Plant a drift in the mulched strip out near the branch tips rather than against the trunk.
Sweet Alyssum
Alyssum blooms from spring to frost and its shallow flowers feed adult hoverflies, whose larvae eat aphids. Orchard trials with flowering ground covers show lower aphid numbers on nearby trees, so a sown band under the canopy earns its space.
Phacelia
Phacelia is one of the strongest nectar plants for bees and small parasitic wasps. Sown in a strip beside the tree it flowers about eight weeks later than pear bloom, keeping beneficial insects on site through the aphid and psylla season.
Nasturtium
Nasturtium can pull black aphids onto its own stems, where they are easy to spot. It only helps if you pull and bag the infested plants; left alone under the tree it becomes an aphid nursery instead of a trap.
Chives
Gardeners have long ringed pear and apple trunks with chives, saying the onion smell throws off aphids hunting by scent. The evidence is thin, but the clumps do no harm, hold the soil at the trunk, and their spring flowers feed early hoverflies.