Residual Effects of Glyphosate Herbicide in Ecological Restoration

Abstract

This study assesses the risks in ecological restoration arising from transplanting into soil containing glyphosate residues. Four Australian restoration species were grown for 60 days in nonadsorbing media treated continuously with glyphosate to establish threshold concentrations for damage. Visual signs of injury were observed in three species, and severe effects on root growth in all species, at solution concentrations as low as 18 mg/L. Only the perennial grass Themeda sp. died at this concentration, with other species surviving at concentrations in the range 36-360 mg/L, beyond which all plants died. Fourteen days exposure followed by removal of glyphosate from root media produced similar effects. Field and glasshouse experiments with the relatively tolerant tree species Angophora costata showed that application rates in the range 10-50 L/ha of herbicide product (360 g/L) would be needed to sustain damage to young plants transplanted into soil typical of local restoration sites. The volume of spray delivered using a handoperated sprayer varied between operators by 5-and 10-fold to complete the same tasks, at the high end presenting a potential risk to the most tolerant species under field conditions, even when spray concentrations follow label instructions. For all but the most sensitive species, the risk of glyphosate residues in ecological restoration should be minimized by training operators of unregulated applicators to deliver controlled volumes of herbicide when spot spraying prior to transplanting.

Seletividade de herbicidas em mudas das espécies nativas Acacia polyphylla, Enterolobium contortisiliquum (Fabaceae), Ceiba speciosa e Luehea divaricata (Malvaceae)

“…Logo, torna-se necessário compreender os mecanismos de desenvolvimento e sobrevivência de espécies nativas (Doust et al, 2008;Lacerda & Figueiredo, 2009). Em campo, é importante estabelecer indicadores sobre os efeitos de herbicidas (Gonçalves et al, 2003;Wilkins et al, 2003;Cornish & Burgin, 2005).…”

Seletividade dos herbicidas setoxidim, isoxaflutol e bentazon a espécies arbóreas nativas

“…Assim, mesmo que as espécies exóticas invasoras não venham a competir diretamente por recursos com os indivíduos plantados, elas devem ser controladas, pois ameaçam a integridade do ecossistema e a sobrevivência das espécies nativas (Ogden & Rejmánek, 2005;Regan et al, 2006). Atualmente, as principais técnicas de controle de plantas daninhas utilizadas em reflorestamentos com espécies nativas são a capina mecânica, que apresenta baixo rendimento operacional, e a aplicação de glifosato (Wilkins et al, 2003;Cornish & Burgin, 2005). No caso particular do uso de glifosato, a ausência de seletividade faz com que a aplicação seja realizada de forma dirigida, o que reduz o rendimento e dificulta o controle de plantas daninhas na linha de plantio, havendo ainda riscos de deriva (Yamashita et al, 2006).…”

Does crotalaria (Crotalaria breviflora) or pumpkin (Cucurbita moschata) inter-row cultivation in restoration plantings control invasive grasses?

“…As a result of the environmental vulnerability of riparian areas (Relyea, 2005;Thompson et al, 2006) and risks for water contamination (Blanchoud et al, 2007), the use of herbicide in forest restoration has been the subject of ongoing debate and has raised several concerns. On the other hand, herbicide use, especially of glyphosate, enhances weed control in ecological restoration efforts (Ansley and Castellano, 2006;Carlson and Gorchov, 2004;Cornish and Burgin, 2005). While there is no consensus on the use of herbicides in riparian areas as a safe strategy of weed control in forest restoration, alternative, non-chemical methods of weed control are especially demanded and necessary (Pywell et al, 2010).…”