Brown Lettuce Aphid, Uroleucon pseudambrosiae
(Hemiptera: Aphididae)

The brown lettuce aphid is found throughout the eastern United States and in eastern Canada. It prefers cool weather but is a pest even in Florida. Eggs are deposited on buds, twigs, and foliage of overwintering hosts. In warmer areas, aphids have the ability to remain on lettuce through the winter months. The adults are dark reddish-brown. Legs, antennae, and siphunculi (cornicles) are black. The brown lettuce aphid can be a serious pest because of its ability to colonize the interior portions of leaf heads. This characteristic makes detection and removal difficult. Populations may be detected by sampling seedlings and sampling the edges of fields since infestations begin with field margins.

Host plants that are attacked by the lettuce aphid include chicory, radicchio, and lettuce. Weed species that serve as hosts are sowthistle, wild lettuce, horseweed, Carolina false dandelion, and dandelion in the family Asteraceae. Few natural enemies are, as yet, identified. Young plants are often treated with an insecticide before transplanting to guard against infestation. Systemic insecticides are usually recommended if the aphids are detected. Cultural control practices include destruction of crop residue and destruction of weeds that serve as alternate hosts.

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Brown lettuce aphid, Uroleucon
pseudambrosiae, colony of mixed
ages and wing forms.
(Photographer: J. Castner,
University of Florida)

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The nymphs and one adult of the brown lettuce aphid,
Uroleucon pseudambrosiae, a pest of lettuce.
(Photographer: J. Castner, University of Florida)

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