Efficacy and phytotoxicity of lime sulphur in organic apple production

Abstract

Curative and preventive efficacy and phytotoxicity of lime sulphur spray schedules, based on a warning system, were evaluated in the Netherlands during two growing seasons under field conditions. In most cases, lime sulphur treatments applied either curatively or preventively resulted in significantly lower scab damage on both the leaves and fruits compared to wettable sulphur treatments. However, all lime sulphur treatments showed high phytotoxicity values, reduced leaf size and had a tendency to a reduced yield quality compared to all other treatments. For curative schedules of lime sulphur on scab control, phytotoxicity and yield did not differ significantly from preventive schedules of lime sulphur. However, the use of a warning system combined with curative schedules of lime sulphur saved one and two lime sulphur sprays in 2000 and 2001, respectively, compared to the preventive treatments of lime sulphur. Our results demonstrated that a curative spray programme with lime sulphur at 0.75-2%, applied 35-45 h after predicted infection periods, can provide effective primary apple scab control, but no benefit in either yield or fruit quality was reached under organic growing conditions. Moreover, research herein clearly showed that organic growers are forced to find a balance between good efficacy and phytotoxic effects of lime sulphur.

Managing Apple Crop Load and Diseases with Bloom Thinning Applications in an Organically Managed ‘Honeycrisp’/‘MM.111’ Orchard

“…(when the maximum temperature was 24°C) resulted in lower crop load and higher fruit russet ratings than those of Regalia Ò treatments applied on the same day. LS is known to be phytotoxic and may result in several undesirable side effects, including increased russet and reduced photosynthesis, especially when applied during warmer temperatures (Holb et al, 2003;Hyre, 1939;McArtney et al, 2006;Palmer et al, 2003). Our results indicate Regalia Ò can be applied during bloom with lower phytotoxicity risk than LS.…”

“…Additionally, LS is caustic and often causes fruit russeting, therefore reducing the value of the fruit . Other negative impacts of LS result from its phytotoxicity, which disrupts photosynthesis, and thus potentially yield, tree growth, and return bloom (Holb et al, 2003;McArtney et al, 2006). Additionally, LS can be a very potent bloom thinner and may over thin the crop in some years.…”

Toxicity of organic farming‑compatible products to the coffee leaf miner

“…It is also important to note that no symptoms of phytotoxicity were recorded on coffee plants treated with any lime sulphur tested concentration. Injury due to lime sulphur spraying has been reported for other plants such as apple and citrus (Smilanick & Sorenson, 2001;Holb et al, 2003). Moreover, the enriched Bordeaux mixture (Viça Café Plus) and the "supermagro" biofertilizer showed no insecticidal effect against L. coffeella, despite their current use by organic coffee farmers.…”

“…Concentrations were chosen based on field rates used by organic coffee farmers, and on the results obtained from the laboratory experiments. Higher concentrations were not tested, due to the possibility of causing phytotoxicity symptoms, as reported for other crops (Holb et al, 2003;Palmer et al, 2003).…”

“…It is a well-known fungicide (Smilanick & Sorenson, 2001;Holb et al, 2003) and pesticide against mites and scales (Afonso et al, 2007;Beers et al, 2009;Kim et al, 2010;Venzon et al, 2013). However, its efficacy against lepidopteran pests has not been documented yet.…”