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1 June 2013 Host Impact and Specificity of Tortoise Beetle ( Cassida rubiginosa) on Canada Thistle ( Cirsium arvense) in Iran
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Abstract

This study determined the potential of the tortoise beetle (Coleoptera: Chrysomelidae) to control Canada thistle (Asteraceae) in Iran. Genetic analysis of the tortoise beetle, based on mitochondrial DNA, confirmed the presence of the species in Iran. A field experiment using five insect densities (0 to 20 larvae plant−1) showed a positive correlation between the number of larvae transferred and impact. Feeding by 20 larvae reduced total biomass of Canada thistle by 78% and the number of capitula by 94%. More important, when grown in competition with wheat, four and eight egg batches (corresponding to approximately 12 and 24 larvae) per Canada thistle plant increased wheat ear weight by 46 and 82%, respectively. Host range studies with 22 crop and 21 weed species using no-choice and multiple-choice tests under laboratory and field conditions and parallel data from a field survey showed that joint feeding and oviposition were restricted to Canada thistle and a few other weed species. Limited feeding, without oviposition, was recorded on an additional seven weed species but also on safflower (10 to 15% reduction in biomass), and common sunflower (< 10%); the latter only under no-choice conditions. The growing period of either crop species, however, does not coincide with the feeding period of the tortoise beetle in the field. Findings indicate that the tortoise beetle is a promising biological control agent for Canada thistle in arable crops and grasslands in Iran. Other complementary methods will likely be needed to prevent substantial yield losses.

Nomenclature: tortoise beetle, Cassida rubiginosa Müller; Canada thistle, Cirsium arvense (L.) Scop.; common sunflower, Helianthus annuus L.; safflower, Carthamus tinctorius L.; wheat, Triticum aestivum L.

Este estudio determinó el potencial del escarabajo Cassida rubiginosa (Coleoptera: Chrysomelidae) para controlar Cirsium arvense (Asteraceae) en Irán. Análisis genéticos de C. rubiginosa, basados en ADN mitocondrial, confirmaron la presencia de esta especie en Irán. Un experimento de campo usando cinco densidades del insecto (0 a 20 larvas por planta) mostraron una correlación positiva entre el número de larvas transferidas y su impacto. La alimentación de las 20 larvas redujo la biomasa total de C. arvense en 78% y el número de capítulos florales en 94%. Más importante aún, cuando la maleza creció en competencia con trigo, cuatro y ocho grupos de huevos (equivalentes a 12 a 24 larvas aproximadamente) por planta de C. arvense incrementaron el peso de la espiga del trigo en 46 a 82%, respectivamente. Estudios de laboratorio y campo con 22 cultivos y 21 especies de malezas para determinar el rango de hospederos, usando pruebas sin alternativa o con alternativas múltiples y datos paralelos de estudios observacionales de campo, mostraron que la alimentación y la oviposición se limitó a C. arvense y unas pocas especies de malezas. Alimentación limitada, sin oviposición, se observó en siete especies de malezas adicionales y en cártamo (10 a 15% reducción de biomasa) y en girasol (<10%); y en este último caso solamente en condiciones sin alternativa. Sin embargo, el período de crecimiento para cualquiera de las especies de cultivos, no coincide con el período de alimentación de C. rubiginosa en el campo. Estos descubrimientos indican que C. rubiginosa es un agente p

Ghorbanali Asadi, Reza Ghorbani, Javad Karimi, Alireza Bagheri, and Heinz Mueller-Schaerer "Host Impact and Specificity of Tortoise Beetle ( Cassida rubiginosa) on Canada Thistle ( Cirsium arvense) in Iran," Weed Technology 27(2), 405-411, (1 June 2013). https://doi.org/10.1614/WT-D-12-00085.1
Received: 22 May 2012; Accepted: 1 November 2012; Published: 1 June 2013
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