Olive leaf spot (OLS), also known as olive peacock spot and cycloconium, is a geographically persistent olive tree disease that is caused by the fungal pathogen Spilocaea oleaginea. It is expressed as a periodic, chronic disease, especially in susceptible regions, and causes significant financial loss for olive farmers, reaching yield losses of up to 10% to 20%. (1)
Traditional management practices are limited to precautionary spraying with various copper-based solutions, such as the Bordeaux mix, around the typically expected period for each location. Depending on the susceptibility of the olive orchard in a specific location, olive farmers typically spray anywhere from 3 to 7 times every season to keep the olive leaf spot and other fungal diseases in check. This can result in soil and aquifer pollution with excessive concentrations of copper. (2)
The NOVATERRA project aims to reduce the negative impacts of plant protection products in olive orchards and vineyards. In this context, the project’s consortium partners of Work Package 3 (WP3) work on developing and testing an advanced Decision Support System (DSS) that will allow olive farmers to monitor OLS risk and spray at exactly the right time. This helps farmers avoid increased orchard management costs, save numerous working hours, and boost the biodiversity of orchard soils.
1. Trial context
In the context of WP3, HORTA provided the outputs of its predictive disease models via web services, to be displayed in the NOVATERRA DSS developed by AGENSO. The DSS utilisation for the management of the OLS was tested in the olive orchards of MYROLION by Athanasios Demeslis under the supervision of the Universitat Politècnica de Catalunya (UPC) in 2022 and 2023.
1.1 Trial Design
The olive orchard trial was segmented into the following plots, each consisting of three trees:
- Sub-plot 1 is managed traditionally (blue)
- Sub-plot 2 is managed according to the NOVATERRA DSS (yellow)
- Sub-plot 3 is left untreated (red)
For each management type, three replications were conducted.
Image 2.1.1 – Trial design; weather station located at the green temperature icon.
The three plots were evaluated based on:
● Management costs, including fuel, maintenance, consumables, and wages.
● Working hours
● OLS intensity (symptomatic leaves per plot at peak as defined by NOVATERRA DSS)
The untreated plots do not yield any results for management costs and working hours. This comparison applies only between the conventional treatment and the treatment based on the NOVATERA DSS. All three sub-plot types are compared based on the effect of the disease on the trees. The average sub-plot is 200 square meters (0.02 ha). The work hour and management cost multiplier should be 50 to assume the total cost per hectare.
1.2 NOVATERA DSS
A weather station that was provided by AGENSO was installed in the olive orchard to directly feed the NOVATERA DSS with weather data. There was no weather station previously installed on the farm; as a result, it is not possible to compare weather data between stations.
Image 2.2.1 – AGENSO weather station installed in Myrolion olive farm.
In addition, access was given to the ardeusi.gr platform, created by AGENSO, to gain access to local weather forecasting and historical weather data starting from April 10, 2022, when the weather station was installed.
Image 2.2.2 – Measurements tab on ardeusi.gr platform with weather data from 10/04/2022 to 30/09/2023.
Access to NOVATERRA DSS was provided. NOVATERRA DSS offers public information regarding OLS risk on a daily basis.
Image 2.2.3 – Daily risk for OLS in Magnesia, Greece.
A user who is registered in the NOVATERRA DSS can receive both forecasts and historical data regarding the risk of OLS.
Image 2.2.4 – Spraying timing, powdery mildew, and OLS presence risk for 31/3/2022.
The risk of OLS in the NOVATERRA DSS ranges from 0 to 3, specifically:
- 0 = No risk
- 1 = Low risk
- 2 = Medium risk
- 3 = High risk
1.3 Field Monitoring
To calibrate the NOVATERRA DSS risk forecasts and determine the ideal spraying timing, on-site visits were performed periodically to monitor the orchard’s state for every risk level. The following table depicts the decision-making process for spraying, based on the NOVATERRA DSS and on-site visits:
| NOVATERRA DSS Risk Level | Other Factors | Effect on the Orchard | Spray? |
| 0 | – | No effect | NO |
| 1 | – | No effect | NO |
| 2 | – | Small groups of trees located in susceptible microclimates and geographical relief are affected by OLS | NO |
| Extended period of high humidity forecast | Small groups of trees located in susceptible microclimates and geographical relief are affected by OLS | YES | |
| 3 | – | Uniform OLS presence over an extended geographical area | YES |
Table 2.3.1 – Decision-making for spray timing based on NOVATERRA DSS.
It was observed that a risk level of 2 by itself does not yield a financially meaningful need for applications against OLS, specifically in the locality of Myrolion’s olive orchards. However, this risk level acts as a marker for a potential elevation to risk level 3. Since a new risk level is provided daily by the NOVATERRA DSS, it is important to monitor the weekly weather forecast to determine whether to spray.
2. Applications
Throughout 2022, the climatic conditions were not suitable for OLS to grow in Myrolion’s olive groves. As a result, the sub-plots related to NOVATERRA DSS were not sprayed. On the contrary, the conventionally treated sub-plots were sprayed three times throughout the growing season.
| Date | NOVATERRA DSS Treatment | Conventional Treatment | OLS Risk |
| 23/02/2022 | NO | YES | N/A |
| 15/04/2022 | NO | YES | N/A |
| 20/10/2022 | NO | YES | 1 |
| 15/02/2023 | NO | YES | 1 |
| 17/04/2023 | YES | YES | 2 |
| 09/09/2023 | YES | YES | 2 |
Table 3.0.1 – Applications in 2022 and 2023.
On 17/04/2023 and 09/09/2023, it was determined to spray despite the medium-level risk because the weather station forecasts portrayed an extended period of high humidity, rain, etc.
Image 3.0.2 – OLS risk from 16/04/2023 to 18/04/2023.
It is important to note that a day after these dates, specifically on 18/04/2023 and 10/09/2023, the risk level elevated to “high.” Accordingly, an increased OLS presence was observed in Myrolion’s olive groves a few days later.
Image 3.0.3 – OLS presence in untreated sub-plots in April and May 2023.
3. Results
In 2022, there was no financially significant OLS presence. Accordingly, the NOVATERRA DSS risk was not elevated. As a result, NOVATERRA DSS-treated sub-plots did not receive any applications. On the contrary, conventional sub-plots received 3 treatments throughout 2022, which translates to a cost of 18 work hours and 844.64 EUR.
| Treatments | Work Hours per Hectare | Cost per Hectare (EUR) | Incidence | |
| NOVATERRA DSS Sub-plots | 0 | 0 | 0 | Low |
| Conventional Sub-plots | 3 | 18 | 844.64 | Low |
Table 4.0.1 – 2022 Treatments, Work Hours per Hectare, and Cost per Hectare.
Since there was no OLS pressure in 2022, it is not possible to calculate financial losses from OLS in the untreated sub-plots.
As of this report, the 2023 trial is still ongoing.
In 2022 and 2023, the NOVATERRA DSS helped minimise applications, thus reducing cultivation costs and environmental impact without leading to an increased financial loss from OLS.
