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.
|Common name||Amount per acre**||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Sivanto Prime)||10.5–12 fl oz||12||1 (foliar)
|MODE-OF-ACTION GROUP NUMBER1: 4D|
|(Admire Pro)||7–10.5 fl oz||12||21|
|MODE-OF-ACTION GROUP NUMBER1: 4A|
|COMMENTS: Apply as a soil application. Do not apply more than 0.38 lb a.i. of imidacloprid/acre per year.|
|(Beleaf 50SG)||2–2.8 oz||12||0|
|MODE-OF-ACTION GROUP NUMBER1: 9C|
|(Movento)||4–5 fl oz||24||3|
|MODE-OF-ACTION GROUP NUMBER1: 23|
|(Dimethoate 400EC)||0.5 pt||48||Leaf lettuce: 14|
|MODE-OF-ACTION GROUP NUMBER1: 1B|
|COMMENTS: Some products only allow use on leaf lettuce; read label to confirm type of lettuce product is registered for.|
|(Assail 70WP)||0.8–1.2 oz/acre||12||7|
|MODE-OF-ACTION GROUP NUMBER1: 4A|
|COMMENTS: Foliar application. Allow 7 days between applications with a maximum of 5 applications per season.|
|MODE-OF-ACTION GROUP NUMBER1: 9B|
|**||Mix with enough water to provide complete coverage.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|#||Acceptable for organically grown produce.|
|1||Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|