Giant reed is an invasive plant of riparian habitats throughout California and the United States. Glyphosate is approved for controlling giant reed in California. Sources indicate that 1.5% to 5% glyphosate solutions are effective at controlling giant reed. There is little published data on the relative efficacy of different concentrations of glyphosate which can be used to select an appropriate application regime for California habitats. We conducted two field experiments to test the hypothesis that glyphosate concentrations of 1.5%, 3%, and 5% applied as foliar sprays were equally effective at killing giant reed plants. Leaf chlorophyll content and the proportion of living stems declined significantly following treatment with 1.5% or greater solutions of glyphosate. New stems were observed the spring following treatment for plants treated with 1.5% glyphosate. No new stems were observed for plants treated with either 3% or 5% glyphosate. A treatment that included ''bending and breaking'' stems prior to treatment with 5% glyphosate provided control similar to 5% glyphosate alone. There was no there evidence that plants sprayed with only a mixture of the surfactant (Agridex), water, and a marking dye were affected beyond the short-term. These results indicate that 3% or 5% foliar applications with glyphosate were the most effective and consistent treatments for killing giant reed with a single late-season application. This result is especially important if the goal of the treatment program is to minimize the number of treatments, thus reducing labor costs and minimizing impacts on sensitive habitats by reducing the number of site visits. Nomenclature: Giant reed, Arundo donax L. ABKDO.

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1981. Effect of fatty acid salts on the growth of Botrytis cinerea. Can. J.Bot. 59: 491-494. The toxicity of a range of potassium salts of fatty acids was bioassayed against Botrytis cinerea Pers. in agar culture. Growth inhibition increased with number of carbon atoms of the short chain fatty acid salts, reached a peak around C l o (caprate), and then declined. Salts of dicarboxylic acids were nontoxic at the highest levels tested, while the unsaturated C, I:1, undecylenate, was as potent as caprate. Caprate at 0.1% inhibited growth of most B. cinerea isolates tested and prevented the remaining isolates from forming sclerotia. Conidial germination of all isolates was prevented by 0.05% caprate. Discrepancies in the literature regarding control of B. cinerea with soft soaps are suggested to be due to varying fatty acid composition of the soaps used. FURITCH, G. S., W. C. TAN et J. C. HOPKINS. 1981. Effect of fatty acid salts on the growth of Botrytis cinerea. Can. J.Bot. 59: 491-494. On a test6 la toxicite d'une sCrie de sels de potassium d'acides gras, pour Botrytis cinerea Pers. dans des cultures gClosCes. L'inhibition de croissance augmente avec le nombre d'atomes de carbone dans les sels d'acides gras a courtes chaines, elle atteint un pic autour de Clo (caprate) puis elle diminue. Les sels des acides dicarboxyliques ne sont pas toxiques aux plus fortes concentrations testCes, tandis que le composC non saturC C I I : I , l'undCcylCnate, est aussi toxique que le caprate. Le caprate 0,1% inhibe la croissance de la plupart des isolats testCs et empiche les autres isolats de former des sclCrotes. Le caprate 0,05% inhibe complktement la germination conidienne de tous les isolats. Les contradictions dans la littkrature quant au contr8le du B. citlerea par les savons doux sont probablement attribuables la composition variable en acides gras des savons utilisCs.[Traduit par le journal]