How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Nasonovia ribis-nigri
(Reviewed 4/17, updated 4/17)
In this Guideline:
DESCRIPTION OF THE PEST
Lettuce aphid has several color forms, ranging from green to orange to pink. Adult winged and wingless lettuce aphids have black markings on the joints of the legs and antennae. Some of the wingless aphids have many black markings on the top of the abdomen as well. The winged adults are browner than the wingless forms, but also have various black markings.
Lettuce aphid is a relatively new pest of lettuce in California. It can be distinguished from green peach aphid by the fact that lettuce aphid does not have strongly converging antennal tubercles.
Lettuce aphid has a very short life cycle and their numbers can increase rapidly. Lettuce aphids appear to pass the winter as nymphs and adults on lettuce, radicchio, Nicotiana spp., and some other composites.
Lettuce aphid feeds deep inside the plant, toward the center on younger leaves. In head lettuce it is found almost exclusively at the heart of the plant. This aphid does not appear to be an important virus vector.
Naturally occurring predators of the lettuce aphid include syrphid fly larvae and green lacewing larvae. Lady beetles and parasites do not play a significant role in lettuce aphid management. Syrphid flies cannot be purchased from insectaries; they must migrate to an infested field from surrounding areas. Syrphid fly larvae and parasitoids are susceptible to many insecticides, especially spinosad (Entrust, Success).
Organically Acceptable Methods
Organic lettuce producers on California's Central Coast rely on naturally occurring predators to control aphid infestations before harvest. Syrphid fly adults and some other predators feed on nectar and pollen from flowers. Many organic lettuce producers intercrop lettuce with quick-flowering annuals to serve as a source of habitat and food to syrphid adults with the intention of increasing egg-laying by syrphids in nearby lettuce. These include baby's breath (Gypsophila grandiflora) common coriander (Coriandrum sativum), Persian clover (Trifolium resupinatum), and sweet alyssum (Lobularia maritima). Do not use sweet alyssum when Bagrada bug numbers are increasing, as it is one of its favorite host plants.
Monitoring and Treatment Decisions
Monitoring requires care in order not to miss early infestations that are hidden within the lettuce. This aphid has a tendency to disperse in the plant rather than forming colonies as green peach aphid does. Control of this aphid is difficult because of its rapid population growth combined with its preferred locations deep within the head.
UC IPM Pest Management Guidelines: Lettuce
Insects and Other Arthropods
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Insects and Mites:N. C. Toscano, Entomology, UC Riverside