Apple orchards are perennially planted where pesticides are applied to control numerous pests and diseases. The extensive long-term use of fungicides can lead to overall environmental load and resistance risk. This study aims to assess which fungicide-active substances have been used more intensively in the last decade in Latvia, evaluating the overall environmental load using the Pesticide Load Indicator (PLI). It was essential to see whether the amount of active substance usage rises, how it correlates with the total changes of the PLI and which substances are with the highest scores. The other issue was to test the sensitivity of Venturia inaequalis populations to systemic fungicides. Six full-bearing apple orchards that reflected local plant protection practices were selected from the different growing regions of Latvia to analyze fungicide use from 2012 to 2021 and test V. inaequalis populations’ sensitivity to systemic substances difenoconazole and cyprodinil. The PLI demonstrated that the protective fungicides were the most crucial group overall, with the highest potential impact on the environment and human health. Systemic fungicides had a relatively lower environmental impact, but after long-term use, the pathogen population’s sensitivity to difenoconazole and cyprodinil was reduced. Introducing new fungicide classes and biological control agents could help growers improve plant protection strategies against V. inaequalis, reducing the risk of resistance and environmental load.

A two-year trial (2021 and 2022) was performed with five different fungicide and foliar fertiliser application strategies to control apple scab (Venturia inaequalis) in integrated apple orchards in Latvia. A strategy of using inorganic fungicides or combining them with synthetic fungicides was compared to a strategy of applications with only synthetic fungicides and untreated control. Furthermore, two strategies included foliar fertilisers to determine whether they may affect apple scab used alone or combined with synthetic fungicides. The timing of the fungicide applications was based on the risk forecasted by the decision support system RIMpro, and fertilisers were used at certain growth stages of the crop. The disease incidence on untreated fruits on cv. Auksis ranged from 38.3% to 59.6%, and on cv. Ligol from 99.3% to 99.5%. Strategies including synthetic fungicides were the most effective against scab on shoot leaves and fruits. The strategy using only inorganic fungicides was effective for low-inoculum orchards. Combining synthetic and inorganic fungicides provided the best apple scab control strategy on fruits, likely helping reduce the resistance selection pressure and residues of synthetic fungicides. Foliar fertilisers were insufficient to control apple scab; they would supplement existing scab fungicide programs.