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1 April 2013 The Development of an Economic Threshold for Nasonovia ribisnigri (Hemiptera: Aphididae) on Lettuce in Central Spain
Ignacio Morales, Beatriz María Diaz, Alfonso Hermoso De Mendoza, Miguel Nebreda, Alberto Fereres
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Abstract

This study reports economic thresholds for the lettuce aphid Nasonovia ribisnigri (Mosley), based exclusively on cosmetic damage, that is, presence or absence of aphids at harvest time. Field trials were conducted in La Poveda Experimental Farm, Madrid (Spain) during autumn (2004 and 2005) and spring (2005 and 2006). Plants were arranged in plots and just before the formation of lettuce hearts they were infested with different densities of N. ribisnigri. Two days later, half of each plot was treated with tau-fluvalinate (Klartan24AF) and the other half remained as an untreated control. Economic thresholds were obtained from nonlinear regressions calculated between the percentage of commercial plants at the end of the crop cycle for both, treated and untreated semiplots, and the different initial densities of N. ribisnigri per plant. Two criteria were used to consider a commercial lettuce plant: a conservative estimate (0 aphids/plant) and a lax one (<5 aphids/plant). Thus, an economic threshold was established for each season and criterium. The economic thresholds that were obtained with the most and least conservative criteria were in spring 0.06 and 0.12 aphids per plant, and in autumn 0.07 and 0.13 aphids per plant, respectively. These results show that to avoid cosmetic damage, insecticide sprays are required when a very low aphid density is detected in lettuce seedlings soon after transplant.

© 2013 Entomological Society of America
Ignacio Morales, Beatriz María Diaz, Alfonso Hermoso De Mendoza, Miguel Nebreda, and Alberto Fereres "The Development of an Economic Threshold for Nasonovia ribisnigri (Hemiptera: Aphididae) on Lettuce in Central Spain," Journal of Economic Entomology 106(2), 891-898, (1 April 2013). https://doi.org/10.1603/EC12275
Received: 16 July 2012; Accepted: 1 December 2012; Published: 1 April 2013
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KEYWORDS
aphid damage
economic threshold
edibility
lettuce crop
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