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Evaluation of Thermal Implements and Organic Herbicides for Weed Control in a Nonbearing Almond (Prunus dulcis) Orchard

  • Anil Shrestha (a1), Marcelo Moretti (a1) and Nathalia Mourad (a1)


Sustainable weed management strategies are needed for organic orchard systems. A study was conducted in an almond orchard in Fresno, CA from 2009 to 2011. Treatment comparisons included steam, flame, and broad applications of either lemongrass oil or D-limonene. An untreated control was also included. The experimental design was a randomized complete block with four replications. Weekly evaluations on percent weed control were taken and weed biomass was sampled 4 to 8 wk after treatment (WAT). Weed control and biomass differed between seasons but, in general, steam and flame provided as much as 95% control 1 WAT. However, the effects lasted only 3 to 4 wk as new weeds emerged or the treated weeds overcame the suppressive effects of the thermal treatments. Weed biomass was 95% lower in the steam- and flame-treated plots compared with the untreated plots in summer. Both steam and flame were more effective on certain erect-growing broad-leaved weed species than on prostrate-growing weeds and grasses. Lemongrass oil provided very little weed control. However, D-limonene provided up to 95% weed control 1 WAT and in one experiment 53% control was observed up to 5 WAT. This herbicide also resulted in lower weed biomass than the untreated and the thermal-treated plots. Monthly applications of steam or flame or applications of D-limonene every 5 to 6 wk may have to be made to adequately suppress weeds in organic almond orchards. Cost estimates of propane use were $41 to 56 ha−1 and $26 ha−1 for the steam and flame treatments, respectively. The cost of D-limonene was estimated as $275 ha−1. To optimize weed control and costs, these tools may need to be used in combination rather than by themselves.

Se necesitan estrategias sustentables de manejo de malezas para los sistemas de huertos orgánicos. Un estudio se condujo en un huerto de almendra en Fresno, California, de 2009 a 2011. Los tratamientos a comparar incluyeron vapor, flama y aplicaciones totales de aceite de zacate limón o de d-limonene. Un testigo sin control de malezas fue también incluido. El diseño experimental fue un bloque completo al azar con cuatro repeticiones. Se hicieron evaluaciones semanales del porcentaje de control de malezas, y se muestreó la biomasa de las mismas de 4 a 8 semanas después del tratamiento (SDT). El control de malezas y la biomasa difirieron entre los ciclos de cultivo, pero en general las aplicaciones de vapor y flama proporcionaron un control de hasta 95% 1 SDT. Sin embargo, los efectos duraron solamente de 3 a 4 semanas conforme emergieron las nuevas malezas o las malezas tratadas superaron los efectos supresivos de los tratamientos con calor. La biomasa de las malezas fue 95% menor en las parcelas tratadas con vapor y flama, en comparación al testigo no tratado en el verano. Ambos tratamientos, vapor y flama, fueron más efectivos en ciertas especies de malezas de hoja ancha y de crecimiento erecto que en las malezas y zacates de crecimiento rastrero. El aceite de zacate limón proporcionó muy poco control. Sin embargo, d-limonene proporcionó hasta 95% de control 1 SDT y en un experimento se observó 53% de control hasta las 5 SDT. Este herbicida también originó menor biomasa de las malezas que el testigo no tratado y las parcelas de tratamiento termal. Aplicaciones mensuales de vapor o flama o aplicaciones de d-limonene cada 5–6 semanas, tal vez tendrían que hacerse para suprimir adecuadamente las malezas en huertos orgánicos de almendra. Los costos estimados del uso de propano fueron de 41 a $56 ha−1 y de $26 ha−1 para los tratamientos de vapor y flama, respectivamente. El costo de d-limonene fue estimado en $275 ha−1. Para optimizar el control de malezas y los costos, estas herramientas tal vez podrían ser utilizadas en combinación y no individualmente.


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