170 Research Article Received: 5 April 2010 Revised: 30 July 2010 Accepted: 19 August 2010 Published online in Wiley Online Library: 27 October 2010 (wileyonlinelibrary.com) DOI 10.1002/ps.2047 Lepidopteran larva consumption of soybean foliage: basis for developing multiple-species economic thresholds for pest management decisions Regiane Cristina Oliveira de Freitas Bueno, a Adeney de Freitas Bueno, b* Fl´ avio Moscardi, c Jos ´ e Roberto Postali Parra d and Clara Beatriz Hoffmann-Campo b Abstract BACKGROUND: Defoliation by Anticarsia gemmatalis (H ¨ ubner), Pseudoplusia includens (Walker), Spodoptera eridania (Cramer), S. cosmioides (Walker) and S. frugiperda (JE Smith) (Lepidoptera: Noctuidae) was evaluated in four soybean genotypes. A multiple-species economic threshold (ET), based upon the species’ feeding capacity, is proposed with the aim of improving growers’ management decisions on when to initiate control measures for the species complex. RESULTS: Consumption by A. gemmatalis, S. cosmioides or S. eridania on different genotypes was similar. The highest consumption of P. includens was 92.7 cm 2 on Codetec 219RR; that of S. frugiperda was 118 cm 2 on Codetec 219RR and 115.1 cm 2 on MSoy 8787RR. The insect injury equivalent for S. cosmoides, calculated on the basis of insect consumption, was double the standard consumption by A. gemmatalis, and statistically different from the other species tested, which were similar to each other. CONCLUSIONS: As S. cosmioides always defoliated nearly twice the leaf area of the other species, the injury equivalent would be 2 for this lepidopteran species and 1 for the other species. The recommended multiple-species ET to trigger the beginning of insect control would then be 20 insect equivalents per linear metre. c  2010 Society of Chemical Industry Keywords: economic injury level; Pseudoplusia includens; Anticarsia gemmatalis; Spodoptera; insect equivalent 1 INTRODUCTION Integrated pest management (IPM) is based on the principle that insecticides must not be applied before economic damage has occurred. Consequently, to enhance growers’ decision-making process, the economic injury level (EIL) concept was developed as the lowest population density capable of causing economic damage to plants. 1 Similarly, the economic threshold (ET) was developed as the population density at which control measures should be started to prevent an increasing pest population from reaching the EIL. 2 Accurate EILs and ETs are fundamental to increase yield and maintain environmental quality by reducing the unnecessary use of management tactics, especially pesticides. 3 Pursuing this goal has been a challenge to entomologists because there is a lack of information on this subject regarding different pest species and crops. 4 Currently, the recommended ETs for lepidopteran larvae on soybean [Glycine max (L.) Merrill] are slightly different around the world. In Brazil, pest control measures are initiated either when 20 large (≥1.5 cm) lepidopteran larvae are counted per sample cloth (1 m soybean line) or when 30% defoliation (in the vegetative stage) or 15% defoliation (in the reproductive state) is observed. 5 In the United States, it is stated that soybean plants can withstand as much as 35% defoliation up to the blooming period. However, during this stage, and when pods begin to form and fill out, any foliage loss greater than 20% will decrease yield. 6 The tolerance of soybeans for these defoliation levels depends on the cultivar, and such differences are very important for IPM. 7 The ET based on the number of larvae was originally proposed for the velvetbean caterpillar, Anticarsia gemmatalis (H ¨ ubner), which at the time was the most important defoliator insect ∗ Correspondence to: Adeney de Freitas Bueno, Embrapa Soybean, PO Box 231, Londrina, Paran´ a 86001-970, Brazil. E-mail: adeney@cnpso.embrapa.br a University of Rio Verde (FESURV), Rio Verde, Goi´ as, Brazil b Embrapa Soybean, Londrina, Paran´ a, Brazil c Centro de Ciˆ encias Agr´ arias, State University of Londrina, UEL, Londrina, Paran´ a, Brazil d Entomology, Phytopathology and Zoology Department, University of S˜ ao Paulo- ESALQ/USP – Piracicaba, S˜ ao Paulo, Brazil Pest Manag Sci 2011; 67: 170–174 www.soci.org c  2010 Society of Chemical Industry