A during-infection spray strategy using sulphur compounds, copper, silicon and a new formulation of potassium bicarbonate for primary scab control in organic apple production

Abstract

In a field experiment conducted over two growing seasons, the effectiveness and phytotoxicity of inorganic fungicides such as sulphur, lime sulphur, copper, silicon and Armicarb (a new formulation of potassium bicarbonate) was compared with water for the control of primary apple scab infections in Belgium on high, medium and low scab-susceptible cultivars (cvs 'Pinova', 'Pirouette' and 'Reinette des Capucins', respectively). In order to drastically reduce the amount of fungicide applied in the orchard, two approaches were used: (1) a strategy involving spraying during the infection process, before fungal penetration and (2) a tunnel sprayer machine for treatment applications. Under field conditions highly favourable for disease, low rates of elemental sulphur (31.8 and 38.6 kg ha −1 year −1 in 2005 and 2006, respectively) combined with low rates of copper (2.1 kg ha −1 year −1 in both years) provided the best scab control and reduced scab severity on the fruits of cv. 'Pinova' by 97 and 98% compared with water control in 2005 and 2006, respectively. Lime sulphur was much more effective than wettable sulphur and appeared to be efficient at temperatures below 10°C, but its effectiveness against apple scab decreased if the treatments were applied 12-24 h later than in the 'during-infection' spray strategy. Armicarb used alone significantly reduced apple scab severity on the leaves and fruits of the three cultivars compared with the water control. Its effectiveness was as good as wettable sulphur applied using the same timing and dosage. Silicon reduced apple scab on fruits very slightly, but not on leaves. The amounts of wettable sulphur, lime sulphur, copper, silicon and potassium bicarbonate used in this experiment to control apple scab were not phytotoxic, did not increase fruit russet, did increase the yield of each cultivar and did not affect summer density of the beneficial Typhlodromus pyri. The potential and limitations of 'during-infection' spraying as a protection strategy against apple scab in organic farming are discussed.

Management of Apple Scab and Powdery Mildew Using Bicarbonate Salts and Other Alternative Organic Products with Fungicide Effect in Apple Cultivars

“…Potassium bicarbonate and wettable sulphur used separately also reduced the attack on the leaves, but in the smaller scale. 118 As noted in previous studies (Holb et al, 2003;Jamar et al, 2008;Jamar et al, 2010)the treatments applied against apple scab and powdery mildew, after each rain, had several important advantages: no washing effect of products due to the rain; high effectiveness of treatments on spores in germinating phase; prevent new infections.…”

“…The efficiency of bicarbonate salts in controlling apple scab reported in previous studies (Schulze et al, 2003;Ilhan et al, 2006;Tamm et al, 2006;Jamar and Lateur, 2007;Jamar et al, 2007aJamar et al, , 2007bJamar et al, , 2008Jamar et al, , 2010 suggests that this compound could be introduced in apple disease management, with the remark that is not to be used alone, but with other active compounds. Even bicarbonates seem to be effective against scab and powdery mildew, but a long lasting effect cannot be expected, because they are unstable compounds that are highly water-soluble and easily washed off the leaves by a small amount of precipitation (Jamar et al, 2010).…”

Enfermedades foliares del caucho (Hevea brasiliensis Muell. Arg.) establecido en un campo clonal ubicado en el Magdalena Medio Santandereano (Colombia).

“…entre los factores ambientales que precedieron al ataque de los patógenos foliares, se encontró que la alta precipitación precedió entre 1 y 2 meses la aparición de los síntomas (Figura 10). La precipitación se encuentra asociada con las primeras infecciones (Jamar et al, 2008), determinando el desencadenamiento de la aparición de brotes de las enfermedades de las plantas. Figura 7.…”

A Copper-based Fungicide Has Minimal Effects on Tart Cherry Fruit Quantity and Quality

“…x p = pyraclostrobin combined with b = boscalid. w Fungicide common names, brand names, formulations used, and manufacturer: basic copper sulfate (Cuprofix Disperss 20DF; Cerexagri, Inc., King of Prussia, PA, in 2007and Cuprofix Ultra 40 Disperss in 2008and 2009; chlorothalonil (Echo 720; Sipcam Agro USA, Inc., Roswell, GA, in 2007, 2008, and 2009 and Equus 720 SST; Makhteshim Agan North America, Inc., Raleigh, NC, in 2009); fenbuconazole (Indar 75WSP; Dow AgroSciences, LLC, Indianapolis, IN); pyraclostrobin + boscalid (Pristine, BASF Corp., Research Triangle Park, NC); tebuconazole (Elite 45DF; Bayer CropScience, Research Triangle Park, NC); trifloxystrobin (Gem 500SC; Bayer CropScience, Research Triangle Park, NC). Amounts of copper refer to metallic copper equivalent applied.…”

“…McManus et al (2007) concluded that applications of copper-based fungicides did not lead to more defoliation assessed at the time of fruit harvest compared with CLS management programs relying solely on synthetic fungicides. However, the effects of copper-based fungicides on fruit quality are not well understood because reported results are contradictory and the metrics used to evaluate fruit quantity and quality have differed among studies (Holb and Schnabel, 2005;Jamar et al, 2008;Keitt et al, 1937;Lalancette and McFarland, 2007;Palmer et al, 2003). Consequently, the overall aim of the current study was to determine if postbloom applications of copper-based fungicides and leaf bronzing are deleterious to tart cherry fruit.…”