Browsing by Author "Alister, C"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Differential phytotoxicity of glyphosate in maize seedlings following applications to roots or shoot
    (WILEY, 2005) Alister, C; Kogan, M; Pino, I
    The transport and differential phytotoxicity of glyphosate was investigated in maize seedlings following application of the herbicide to either roots or shoots. One-leaf maize seedlings (Zea mays L.) were maintained in graduated cylinders (250 mL) containing nutrient solution. Half of the test plants were placed in cylinders (100 mL) containing different C-14-glyphosate concentrations; the remainder received foliar appliation of C-14-glyphosate. After 26 It, the roots and the treated leaves were washed with distilled water, and the plants placed again in cylinders (250 mL) containing fresh nutrient solution for 5 days. Plants were weighed, and split into root, seed, cotyledon, coleoptile, mesocotyl, first leaf and apex. The recovery of 14 C-glyphosate was over 86%. For both application treatments, the shoot apex was the major sink of the mobilized glyphosate (47.9 +/- 2.93% for root absorption and 45.8 +/- 2.91% for foliar absorption). Expressed on a tissue fresh weight basis, approximately 0.26 mug a.e. g(-1) of glyphosate in the apex produced a 50% reduction of plant fresh weight (ED50) when the herbicide was applied to the root. However, the ED50 following foliar absorption was only 0.042 mug a.e. g(-1) in the apex, thus maize seedlings were much more sensitive to foliar application of the herbicide.
  • Thumbnail Image
    Item
    Effect of glyphosate applied over emerged asparagus spears
    (ELSEVIER SCI LTD, 2004) Alister, C; Kogan, M
    The effect of glyphosate applied directly to asparagus spears on their growth and crowns regrowth capacity was studied during the 2001 and 2002 seasons. Homogeneous asparagus crowns, cultivar UC 157 F1, were planted in individual plastic bags two seasons before application. The effect of spear height (smaller and larger than 12 cm), and one or two glyphosate application as well as the effect of time between the application and spear harvest (2, 24, 48 and 72 h) were determined. The Spears were treated with a commercial formulation of glyphosate (isopropylamine salt) at 2.4 kg ai ha(-1). The experimental design was a factorial with an arrangement of complete randomized blocks with four replications. A clear deformation was observed in the sprayed spears after treatment with glyphosate, which was more evident as the time interval between application and harvest increased. Applied spears harvested within 2h after application did not show any evident deformation. The crown regrowth capacity was not affected by glyphosate application directly to spears, eventhough some did show strong damage at the apex. These results show that glyphosate application directly to spears during the harvest season will not produce damage to the asparagus plants. However, residues of glyphosate on harvested spears might be an important issue. (C) 2003 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Efficacy of imidazolinone herbicides applied to imidazolinone-resistant maize and their carryover effect on rotational crops
    (ELSEVIER SCI LTD, 2005) Alister, C; Kogan, M
    A field study was performed in imidazolinone-resistant maize in order to evaluate the effectiveness and carryover effect on rotational crops of two formulated mixtures of imidazolinone herbicides: imazapyr plus imazapic and imazapyr plus imazethapyr. During the 2003 season the mixtures were applied broadcast to five leaves maize plants at doses of 114 and 228 g ha(-1), both tanks mixed with a 31% petroleum hydrocarbon adjuvant at 125 and 250 mL ha(-1), respectively. Overall weed control varied from 85%, up to 95%. Weed species controlled were Setaria sp., Chenopodium album, Solanum, sp., Amaranthus retroflexus and Digitaria sanguinalis, and Echinochloa cruss-galli whilst Eragrostis sp. was not controlled. Soil activity of the herbicides (carryover) was detected over 10 months after application, imazapyr/imazapic mixture being the most persistent. The sensitivity of rotational crops, from high to low, was the following: Beta vulgaris > Capsicum annum > Lycopersicum esculentum > Cucumis melo > Hordeum vulgare > Medicago sativa > Lolium multiflorum > A vena sativa > Pisurn sativurn > Allium cepa > Zea mays. (C) 2004 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Simazine dynamics in a vineyard soil at Casablanca valley, Chile
    (WILEY, 2005) Alister, C; Lopez, R; Kogan, M
    Field dissipation, soil movement and laboratory leaching studies were performed to elucidate the effect of two rainfall amounts in the behaviour and environmental fate of simazine under climatic conditions at Casablanca Valley, Chile. Dissipation and soil movement were studied in a field vineyard with a sandy loam soil (Inceptisol; 74.08% sand; 14.87% silt and 11.04% clay). Simazine was applied to bare soil at 2.0 kg AI ha(-1), and its concentration was measured using immunoassay (ELISA) at 0, 10, 20, 40 and 90 days after application under two rainfall amounts, natural field conditions (39 mm) and modified conditions (39 + 180 mm). Simazine leaching was studied using soil core PVC lysimeters (0.9 m height; 0.22m diameter). Field dissipation data were adjusted with a bi-exponential model. Half-life (DT50) values varied between 31.3 (+/- 2.5) and 19.0 (+/- 4.2) days under natural and modified conditions, respectively. Simazine K-d varied from 0.42 to 2.15 (K-oc 32.6-216.2) in the soil profile. Simazine was detected at a 90-cm soil depth in concentrations of 0.0085 (+/- 0.0043) mg kg(-1) and 0.0321 (+/- 0.001) mg kg(-1) under field and modified conditions, respectively. The maximum simazine leachate concentrations were 0.013 (+/- 0.00084) mg litre(-1) (0.012% of total applied simazine) and 0.0084 (+/- 0.00082) mg litre(-1) (0.11% of total applied simazine) for field and modified conditions respectively. These data indicate that water quantity has a significant effect on the DT50 and the amount of simazine that moved through the soil profile, but not on the soil depth reached by this herbicide. (c) 2005 Society of Chemical Industry.