Planta Daninha (2011) 29, 279-285

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M.N.P. Henares, F.R.L. Rezende, G.R. Gomes, C. Cruz and R.A. Pitelli (2011)
Eficácia do diquat no controle de Hydrilla verticillata, Egeria densa e Egeria najas e toxicidade aguda para o Guaru (Phallocerus caudimaculatus), em condições de laboratório
[Efficacy of diquat in the control of Hydrylla verticillata, Egeria densa and Egeria najas and its acute toxicity to Phallocerus caudimaculatus, under laboratory conditions]
Planta Daninha 29 (2), 279-285
Abstract: In Brazil, the submerged plants Egeria densa and Egeria najas have caused damage to multiple uses of water. Hydrilla verticillata has been recently introduced, but it has a history as a problem plant in the U.S., Mexico and Australia. The objectives of this work were to assess the relative susceptibilities of these three macrophytes to diquat and the risks of using this herbicide for fish guppy (Phallocerus caudimaculatus). Thus, laboratory assays were set up to assess the relative susceptibility of the three macrophytes. Pointers of these plants were kept in solutions containing 0.0, 0.2, 0.4, 0.8 and 1.6 mg L-1 diquat (Reward®) for 14 days. The evaluation was performed based on the variation of fresh matter weight and length of the pointers during the period of exposure to the herbicide. H. verticillata was more sensitive to diquat, compared with the two Egeria macrophytes, even at low herbicide concentrations. At higher herbicide concentrations, E. densa was more sensitive than E. najas. The risk of applying diquat to P. caudimaculatus was estimated by acute toxicity. Fingerlings of P. caudimaculatus of 0.4 ± 0.2 g were exposed to solutions of 0.0, 1.0, 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 mg L-1 of diquat. The 50% lethal concentration (LC (I) (50.96h)) of diquat estimated for P. caudimaculatus was 7.17 mg L-1. For P. caudimaculatus, acute toxicity was higher than the concentration recommended for the control of submerged plants, indicating very low risk for this fish.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: Portuguese)
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Research topic(s) for pests/diseases/weeds:
control - general
health/environmental effects of pesticides

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Hydrilla verticillata (weed)
Egeria densa (weed)
Egeria najas (weed)