First results of UV light produced by an autonomous rover to control the main apple diseases

An autonomous rover prototype equipped with UVC light panels — developed to protect vineyards from grapevine diseases — was tested for its effectiveness against major apple diseases in a field trial conducted in Trentino (Northern Italy). In the growing season 2024, trials were carried out in three organic apple orchards with different varieties. The autonomous prototype was used either to supplement or completely replace conventional plant protection treatments. The orchards featured a narrow fruit-wall training system for Opal and Inored Story varieties, and a spindle training system for Golden Delicious. Row spacing was 2.6 meters across all sites. No chemical treatments were applied to the Opal and Inored Story, as they are scab-resistant cultivars. In the case of Inored Story, an untreated control plot (receiving neither chemical nor UV treatment) was also included to assess the prototype’s effectiveness against powdery mildew. A different strategy was applied to Golden Delicious, a variety highly susceptible to apple scab. Here, the experimental treatments included: a standard chemical strategy, a combination of low chemical input and low UV dosage, a high UV dosage, and an untreated control. UV dosage was set by adjusting the rover’s speed rather than the intensity of the UV light. The first treatment took place in late March, when conditions began to favour primary scab infections, and the trial concluded in early June. After three treatments, the prototype experienced a mechanical failure and was out of service for four days. It was subsequently repaired and remained operational for the remainder of the trial. Efficacy was assessed using pseudo-replications to enable statistical analysis. Visual inspections were also conducted to check for any negative side effects on vegetation and fruit. Results showed no significant differences between the low and high UV dosages in controlling powdery mildew on Opal (Figure 1), as well as between UV-treated and untreated plots of Inored Story (Figure 2). Due to the rainy spring in 2024, apple scab infection in the untreated Golden Delicious plots was particularly severe (Figure 3), with widespread secondary infections emerging by June. Across all treatment strategies, nearly 100% of shoots in Golden Delicious plots were infected by scab. The average percentage of infected leaves showed significant differences among treatments (χ2 [3]=9.994; p=0.0186). The KruskalWallis test indicated a significant trend when the chemical standard was excluded from the analysis (χ2 [2]=6.140; p=0.0468). Similarly, the average fruit infection rate was clearly lower in the standard chemical treatment compared to the untreated control, while both UV-based treatments were less effective than the standard. Importantly, no negative side effects were observed on either the leaves or the fruit of each variety. The effects of UV radiation on the control of powdery mildew, by employing different radiation doses, should be further investigated. Given the environmental conditions during the trial — particularly favourable to the development of apple scab — the preliminary results of this study seem promising. Additional field trials, carried out throughout the entire growing season, will be necessary to further evaluate the efficacy of UV light on apple diseases and to understand how this technology could partially replace or complement conventional plant protection strategies. The use of UV light and autonomous equipment could be considered as part of precision crop protection strategies aimed at developing low input approaches for apple orchards