Impact of introduced native herbivores on a Pistia stratiotes infestation close to the Paraná Delta in Argentina

ABSTRACT

Pistia stratiotes L. (Araceae) is an important weed in many waterways worldwide. The South American weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae) and the planthopper Lepidelphax pistiae Remes Lenicov (Hemiptera: Delphacidae) are specific herbivores of P. stratiotes. Both species, plus the oligophagous moth Samea multiplicalis Guenée (Lepidoptera: Crambidae), were released in a P. stratiotes-infested lake in the suburbs of Buenos Aires, Argentina, where previous sampling indicated that specific herbivores were absent. The weevil and the planthopper established and covered the whole lake in under two months. The moth may have also established but its numbers were very low and erratic. Plant cover, biomass per square metre, and individual plant size decreased markedly within a year after the release of the insects. Concomitantly, other floating macrophytes appeared in the lake. Insect abundance was related to mean monthly temperature and light hours, but not the other insect species. However, insect damage levels and the state of the plant population suggest that herbivory was the main factor in lowering the P. stratiotes populations. N. affinis and L. pistiae could be specific, damaging and compatible as biocontrol agents for P. stratiotes.

KEYWORDS:

• Neohydronomus affinis
• Lepidelphax pistiae
• aquatic weeds
• herbivore competition
• weed biocontrol

Acknowledgements

We wish to thank the Dirección de Producción Limpia y Gestión Ambiental of the Municipality of Vicente López for allowing us to carry out these tests, and for their support at the REVL; Alejandro Perez Bisbal and Mario Lafont for their help and support in the field.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partly funded by the USDA-ARS-Invasive Plant Research Laboratory, Ft. Lauderldale, FL.