Coca (Erythroxylum coca) control is affected by …

1 930 Journal of Toxicology and Environmental Health, Part A, 72: 930 936, 2009 ISSN: 1528-7394 print / 1087-2620 online DOI: ( erythroxylum coca) control is affected by glyphosate Formulations and AdjuvantsCoca control is affected by GlyphosatesE. J. P. Marshall1, Keith R. Solomon2, and Gabriel Carrasquilla31 Marshall Agroecology Limited, Barton, Winscombe, Somerset, United Kingdom, 2 Centre for Toxicology and Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada, and 3 Facultad de Salud, Universidad del Valle, Valle, ColombiaThe aerial spray program for the eradication of coca inColombia uses Glyphos, a local formulation of glyphosate tank-mixed with an adjuvant product, Cosmo-Flux.

2 There are somepotential risks to amphibians from direct overspraying of shal-low waters. In order to evaluate potential alternative mixtures, afield experiment was conducted at the Center of National Train-ing of Police Operations in Tolima province, Colombia. Plants ofcoca were established with irrigation and grown to 75 cm tall. Arandomized split-plot design experiment was laid out andsprayed with a range of glyphosate formulations and differentadjuvants using an experimental ground sprayer. Assessmentswere made of plant vigor, height, and above-ground standingcrop (fresh weight) 3 wk after application. Resprouting of plantswas assessed at 9 wk after treatment.

3 Unformulated glyphosateapplied as the product Rodeo gave poorer control of coca thantwo formulated products, Roundup Biactive (from Europe) andColombian Glyphos. In general, these products performed wellwithout added adjuvants, giving control similar to that of theeradication mixture with Cosmo-Flux. There was some evidencethat addition of the adjuvant Silwet L-77 and to a lesser extentMixture B (from the United Kingdom) gave more rapid herbi-cide symptoms. There were also indications that glyphosaterates of less than kg acid equivalents ( )/ha couldgive control in the range of 95%. Depending on the environmen-tal risk requirements, the experiment indicates that, shouldother spray mixtures be required, there are potential alterna-tives.

4 These would require extensive field testing to cover differ-ent environmental conditions, different coca varieties, andparticularly aerial application, prior to a the glyphosate product require changing, RoundupBiactive may be considered. Should the adjuvant require chang-ing, then on the basis of this research, Silwet L-77 and Mixture Bwould be good candidates for further control of the drug plant erythroxylum coca Lam. andthe closely related E. novogranatense (coca), the sources ofcocaine, is the focus of considerable effort and expenditure ina number of South American countries. Authorities are tar-geting the removal of the plant and are also engaged in ruraldevelopment projects to replace the illicit cultivation of thiscrop.

5 As well as controlling supplies of the drugs, there arealso efforts to reduce global demand for the drug. The illicitcocaine industry has an estimated production that reached thestreets of 600 tonnes in 2007 with a retail value of approxi-mately $934 million. Retail prices are $2200/kg in Colombia,$10,200/kg in the United States, and $85,000/kg in the streetsof Europe (UNODC, 2007). As part of the supply controleffort that started in the 1970s, an aerial spraying eradicationprogram in Colombia was started in 1997 using the herbicideglyphosate. The area of coca sprayed with glyphosate hasshown a steady increase over recent years, reaching 153,000ha in 2007 (personal communication, National Police ofColombia, Bogot , December 2007).

6 The aerial spray program is conducted with two types ofcommercial crop-spraying aircraft fitted with Accu-Flo air-induction nozzles. The spray planes, Air Tractor 802 (AirTractor Inc., Olney, TX) and Rockwell OV-10, are equippedwith high-resolution tracking equipment and positional datarecorders that display position, provide directional guid-ance, and store data for later analysis (Solomon et al.,2007). glyphosate used for the aerial eradication program inColombia is the Glyphos product containing 354 g acid equiva-lents ( )/L sold for agricultural use. glyphosate was found tobe effective at controlling both species of coca, E. coca and E. General Secretariat of the Organization of American States,2009.

7 This paper was prepared as part of a Study entitled Productionof Illicit Drugs, the Environment and Human Health, financed withcontributions from the Governments of Colombia and the UnitedStates of America. The conclusions and opinions expressed herein arethose of the authors and not necessarily those of the Organization ofAmerican States and its General Secretariat, which as of the date ofthis copyright, have not formulated any opinion with respect to authors thank Samuel Rodriquez and Oscar Mendez for theirwork in the field and for maintaining the correspondence to Dr. E. J. P. Marshall, MarshallAgroecology Ltd, 2 Nut Tree Cottages, Barton, Winscombe, Somerset,BS25 1DU, UK.

8 E-mail: with copy At: 20:07 2 October 2009 COCA control IS affected BY GLYPHOSATES931novogranatense (Ferreira et al., 1997). The aerial applicationrate of glyphosate is kg in Colombia. To maximizepenetration and effectiveness of the spray formulation, glypho-sate is tank-mixed with an adjuvant product (CosmoFlux 411F;Cosmoagro, Bogot ). The inclusion of the adjuvant follows thestudies of Collins and Helling (2002), who demonstrated afourfold increase in glyphosate efficacy by including suitableadjuvant mixtures in the , such as the polyethoxylates in Cosmo-Flux,enhance efficacy through (1) increasing target surface adher-ence, (2) promoting better droplet spread, (3) better disper-sion, (4) prevention of aggregation, and (5) enhancedpenetration of herbicides into target plant tissues through thereduction of surface tension on plants.

9 Surfactants also dis-rupt the water-insoluble wax cuticle, thus increasing the pen-etration of herbicide active ingredient. Base oils, such as theisoparaffins in Cosmo-Flux, are another class of adjuvantsused in pesticide formulations to primarily aid foliar absorp-tion of the pesticide by disrupting the waxy cuticle on theouter surface of foliage, which increases permeability(Solomon et al., 2007).Environmental risk assessments of the aerial eradicationprogram indicated that the relative impact of the glyphosatemixture is small in comparison with the impacts of forest clear-ance for cropping (Solomon et al., 2007). Nevertheless, therecould be some impact on amphibian species in shallow waters(<30 cm deep) that are directly oversprayed.

10 Such effects areunlikely to be due to glyphosate , but to the adjuvants present inthe spray mixture. Further ecotoxicological tests were con-ducted with the spray mix as used in Colombia (Bernal et al.,2009a, 2009b). Developments in adjuvant research indicatethat it may be possible to identify an adjuvant mixture or mix-tures as effective as the current mixture, but with less risk tonative field experiment described here was conducted as aninitial step to evaluate the efficacy of a range of glyphosate for-mulations mixed with different adjuvants. It was postulatedthat alternative combinations might give as good or better con-trol of coca than the formulation currently used in the aerialeradication program.