Poplar petiole gall aphid (Pemphigus populitransversus)
Pest description and damage There are nearly a dozen aphids that feed on poplar leaves, petioles, stems, and bark. Many have herbaceous alternate hosts such as the poplar-lettuce root aphid. This aphid can be distinguished from other aphids by their short antennae (less than one-third body length) and undeveloped cornicles. These aphids feed on the leaf petioles, or along the midrib causing these tissues to enlarge and enclose the aphids. The hard, pale green, rounded galls form along the petiole or at the base of the leaf or as a swelling along the midvein. Aphids inside the galls appear grayish and waxy. The leaves are not damaged, but may be turned at right angles to the petiole. Aphids cause little damage to poplars, but may be serious pests to their summer hosts such as mustard, buttercup, lettuce, turnip, beet and sugar beet, and aster.
Biology and life history Where lettuce or related weeds are not available, these aphids overwinter in the egg stage on the bark of Lombardy poplar. They develop to adults and reproduce once on poplar before migrating to summer hosts in Brassica or Aster species. In late summer, winged forms reappear, and these migrate back to poplar to mate and lay eggs.
For biology, life history, monitoring and management
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