Insect herbivores associated with Nymphaea mexicana (Nymphaeaceae) in southern United States: potential biological control agents for South Africa
Potential biological control agents for South Africa
Abstract
Nymphaea mexicana Zuccarini (Nymphaeaceae) (Mexican waterlily) is an emergent floating-leaved aquatic plant from the southeastern USA that is invasive in South Africa. In invaded waterbodies this plant restricts water movement, increases siltation, decreases recreational activities, and can deplete water oxygen levels, which in turn negatively impacts aquatic fauna. Currently there are no chemical, mechanical, or biological control programs in place for N. mexicana in South Africa, but the sustainability of biological control makes this the most desirable option. Field surveys for potential biological control agents were conducted in the native range of N. mexicana in Florida, Louisiana, and Texas from Aug to Oct 2018. Leaves, stems, flowers, and roots of N. mexicana were searched for insect herbivores by hand and using Berlese funnels. Insects were prioritized for use as biological control agents by considering the extent and type of feeding damage, field host range, and incidence (percentage of sites in which each species was found). In total, 15 confirmed species were found feeding on N. mexicana, and some taxa were identified only to family level. Incidence coverage estimator mean, MMRuns, Chao 2 mean, and Chao 2 upper 95% CI species accumulation estimators predicted that between 2 and 5 species were missed during the surveys. Based on field observations, Bagous americanus LeConte (Coleoptera: Curculionidae), and Megamelus toddi Beamer (Hemiptera: Delphacidae) were prioritized. Host specificity trials will be conducted to determine whether these insects may be used as biological control agents of N. mexicana.
Key Words: field surveys; Mexican waterlily; yellow waterlily; invasive alien plant
Resumen
Nymphaea mexicana Zuccarini (Nymphaeaceae) (Mexican waterlily) es una maleza acuática emergente nativa del sureste de Estados unidos, y considerada invasiva en África del Sur. En humedales invadidos, esta planta limita el movimiento de agua, incrementa sedimentación, decrece el valor recreacional, y puede reducir los niveles de oxígeno líquido, lo cual impacta negativamente la fauna acuática. No existe programas de control químico, mecánico o biológico para N. mexicana en África del Sur, pero la sostenibilidad del control biológico hace esta opción las más deseable. Desde Agosto a Octubre del 2018 se realizaron muestreos de campo para recolectar agentes de control biológico en el rango nativo de N. mexicana en Florida, Luisiana, y Texas. Insectos herbívoros de hojas, tallos, flores, y raíces de N. mexicana fueron buscados a mano o con embudos de Berlese. Insectos fueron priorizados para el uso como agentes de control biológico dependiendo del tamaño y tipo de daño, el rango de hospederos de campo, y su densidad de campo (porcentaje de sitios en los cuales la especie fue encontrada). Quince especies fueron encontradas alimentándose de N. mexicana, y posiblemente más están presentes debido a que taxones fueron identificados al nivel de familia. Los estimadores de especies acumulados media estimador de cobertura de incidencia, NMRuns, media Chao, y Chao por arriba del 95%, predijeron que entre dos y cinco especies no fueron encontradas durante los muestreos. Basado en observaciones de campo, Bagous americanus LeConte (Coleoptera: Curculionidae), y Megamelus toddi Beamer (Hemiptera: Delphacidae), fueron priorizados. Ensayos de especificidad serán realizados para determinar si esos insetos pueder se usados como agentes de control biológico de N. mexicana.
Palabras Clave: muestreos de campo; Ninfa Mexicana; Apapatla; planta invasive
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