Role of Syrphid Larvae and Other Predators in Suppressing Aphid Infestations in Organic Lettuce on California’s Central Coast

Organic lettuce, Lactuca sativa L., growers on the Central Coast of California rely on conservation biological control to manage Nasonovia ribisnigri Mosley (Hemiptera: Aphididae) and other aphid pests of lettuce. In 2006, we carried out five replicated field trials to determine the importance of sy...

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Bibliographic Details
Published in:Journal of economic entomology 2008-10, Vol.101 (5), p.1526-1532
Main Authors: Smith, Hugh A, Chaney, William E, Bensen, Tiffany A
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Animals
aphid predators
Aphids - parasitology
Biological and medical sciences
Biological and Microbial Control
California
conservation biocontrol
Control
Diptera - growth & development
Drug Combinations
Food, Organic
Fundamental and applied biological sciences. Psychology
General agroecology
General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping
General agronomy. Plant production
Generalities
Generalities. Agricultural and farming systems. Agricultural development
insectary crops
Insecticides
Lactuca
Larva - physiology
Macrolides
organic agriculture
Pest Control, Biological
Phytopathology. Animal pests. Plant and forest protection
Population Density
Protozoa. Invertebrates
Syrphidae
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Summary:Organic lettuce, Lactuca sativa L., growers on the Central Coast of California rely on conservation biological control to manage Nasonovia ribisnigri Mosley (Hemiptera: Aphididae) and other aphid pests of lettuce. In 2006, we carried out five replicated field trials to determine the importance of syrphid larvae in the suppression of N. ribisnigri and other aphids infesting organic romaine lettuce. We used Entrust, a spinosad-based insecticide approved for use on organic farms, to suppress syrphid larvae in aphid-infested romaine. Romaine treated with Entrust was unmarketable at harvest because of aphid infestation, whereas insecticide-free romaine was marketable. Syrphid larvae composed 85% or more of total predators in most trials, and they were the only predators consistently recovered from romaine that was infested with aphids early and largely aphid-free by harvest. The species mix of nonsyrphid predators varied from site to site. Applications of Entrust suppressed nonsyrphid predators in two trials, and so was an imperfect tool for selectively suppressing syrphid larvae. The relative importance of syrphid larvae and other predators in the conservation biological control of aphids in organic romaine is discussed. We conclude that syrphid larvae are primarily responsible for the suppression of aphids in organic romaine on California’s Central Coast.
ISSN:0022-0493
1938-291X
DOI:10.1603/0022-0493%282008%29101%5B1526%3AROSLAO%5D2.0.CO%3B2