Effectiveness of Low Copper-Containing Chemicals against Olive Leaf Spot Disease Caused by Venturia oleaginea

Abstract

The high level of copper (Cu) accumulation in the soil, the risk of surface water contamination, and the potential public health problems due to Cu entering the food chain have raised concerns on the use of Cu compounds in agriculture, including olive growing. As a consequence, there is worldwide regulatory pressure on agricultural systems to limit the use of Cu compounds. Hence, a field trial was carried out to evaluate the effectiveness of low copper containing chemicals to control olive leaf spot (OLS) disease caused by Venturia oleaginea. The trial was conducted in 2021 in an olive (cv. Nabali Baladi) grove in Palestine. Copper complexed with lignosulphonate and gluconate (Disper Cu Max®) and the self-defense inducer Disper Broton GS® were evaluated and compared to dodine and the traditionally and frequently used copper hydroxide. In addition, untreated trees were used as the control. Treatments were made in March, July, and August. In March 2021, leaves grown in 2020 were present and 100% infected. V. oleaginea infections caused defoliation in untreated and treated olive trees with varying degrees of intensity: the Control had the most defoliation, followed by copper hydroxide and Disper Cu Max®, whereas dodine and, in particular, Disper Broton GS® had the least. All treatments reduced symptomatic leaves but their efficacy varied significantly: copper hydroxide was the least effective, Disper Cu Max® was intermediate, dodine and, mainly, Disper Broton GS® were the most effective. Overall, the results are promising since Disper Cu Max® and Disper Broton GS® were able to significantly reduce OLS damage and the amount of copper used for treatments.

Dodine an effective alternative to copper for controlling Venturia oleaginea, the causal agent of pea-cock eye disease, in highly infected olive trees

“…In other field studies, the use of dodine and copper oxychloride showed similar effects ( Iannotta et al., 2002 ; Belfiore et al., 2014 ; Adawi et al., 2022 ). The differences in the results obtained in the present study with respect to those of Iannotta et al.…”

“…In other field studies, the use of dodine and copper oxychloride showed similar effects (Iannotta et al, 2002;Belfiore et al, 2014;Adawi et al, 2022). The differences in the results obtained in the present study with respect to those of Iannotta et al (2002) and Belfiore et al (2014) may be due to the heavy but still mainly asymptomatic attack of the trees in our study.…”

“…Applications of chemicals containing a low amount of copper is a possible solution. Adawi et al (2022) documented good protection against olive spot disease using copper complexed with lignosulphonic and gluconic acids (Disper Cu Max ® ) and a self-defense inducer (Disper Broton GS ® ), which have a metallic Cu content five and ten times lower than copper hydroxide, respectively. However, copper-free control strategies should be optimized.…”

Olive leaf spot caused by Venturia oleaginea: An updated review

“…Interesting results have been recently obtained with a new formulation containing copper complexed with gluconate and lignosulphonate (Disper Cu Max ® -Eden Modern Agriculture S.L-Spain), which, in spite of the lower content of metallic copper (e.g. five times lower than copper hydroxide), proved more effective than traditional formulations (Almadi et al., unpublished; Adawi et al., 2022 ). The higher efficacy was associated to a supposed cytotropic phytomobility of the formulation, which may also exert a curative action.…”

“…In pot-cultivated olive plants, promising results were obtained with a number of plant resistance inducers, applied as foliar spray or soil drench: acibenzolar-S-methyl, 3-amino butyric acid, chitosan, harpin, laminarin, phosphates (FoliR-Fos 400 ® ), salicylic acid and silicon (Actisil ® ) ( Obanor et al., 2013 ; Nascimento-Silva et al., 2019 ; Tziros et al., 2021 ). Recently, in an open-field trial, a very good protection against V. oleaginea attacks, comparable to the dodine, was demonstrated using the self-defense inducer Disper Broton GS ® ( Adawi et al., 2022 ). This formulation also contains complexed copper with an amount of metallic copper 10 times lower than copper hydroxide.…”