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

Abstract

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.

Efficacy and Cost of Cultivators, Steam, or an Organic Herbicide for Weed Control in Organic Vineyards in the San Joaquin Valley of California

“…However, most of the younger weeds also regrew within a few weeks. These results support other recent findings suggesting that steam has differential effects on various weed species, with succulent weeds and grasses being poorly controlled compared with some other broadleaved weed species (Leon and Ferreira, 2008;Shrestha et al, 2012).…”

“…The steam generating machine was equipped with a propane-powered burner that combusted propane and delivered steam through an adjustable sidearm (canopy). More details of the machine are available in Shrestha et al (2012). The machine was pulled by a tractor at a travel speed of 1.5 mph.…”

“…Handhoeing is another potentially effective weed management practice, though it is prohibitively laborious and expensive. Other examples of alternative weed management practices include the use of steam (Kolberg and Wiles, 2002;Shrestha et al, 2004Shrestha et al, , 2012, flame (Ascard 1998;Ullao et al, 2010), microwaves (Sartorato et al, 2006) reduced soil disturbance cultivators, cover crops, and mulches (Mennan and Ngouajio, 2012). Each of these tools has specific limitations in vineyards and other cropping systems.…”

“…Each of these tools has specific limitations in vineyards and other cropping systems. For example, Shrestha et al (2012) reported that steam, propane flaming, and an organic herbicide (d-limonene) provided 3 to 6 weeks of weed suppression in nonbearing almond (Prunus dulcis) orchards. Thus, repeated applications of these treatments were necessary, which may not be cost-effective.…”

The effects of water steam on weeds and fungal diseases in the stands of onion

“…Another increasingly used weed control method is thermal weed control. Thermal weed control can be used in various crops (Shrestha et al, 2013;Velička et al, 2016) In different countries, diverse methods of thermal weed control are used in organic farms: flaming (Sivesind et al, 2012), combustion gases (Ulloa et al, 2010;2012;Datta, Knezevic, 2013), hot foam (Cederlund, Börjesson, 2016), hot water (De Cauwer et al, 2014) and water steam (Melander, Kristensen, 2011;Shrestha et al, 2012;Vidotto et al, 2013). Researchers have indicated that thermal weed control is more effective than mechanical weed control (Virbickaitė et al, 2006;Ascard et al, 2007).…”