Association of apple powdery mildew (Podosphaera leucotricha) and anthracnose (Neofabraea malicorticis) epidemics with environmental factors and agronomic practices in Chencha highlands, southern Ethiopia

Abstract Apple powdery mildew and anthracnose are widely distributed and major constraints on apple production around the world. The objective of the study was to determine powdery mildew and anthracnose prevalence, intensity, and association between biophysical factors. To this effect, field assessments were conducted in Chencha highlands of southern Ethiopia during the 2021 and 2022 production years. A multistage random sampling approach was followed for data collection, and the association between disease severity and biophysical factors was analyzed using a logistic regression model. A total of 164 apple orchards were inspected in five of the top apple-producing farmer associations (FAs) in the district. Results showed that the diseases were prevalent in apple fields, although the level of importance varied among FAs. Mean powdery mildew and anthracnose severity were lower in 2021 (23.56 and 22.39%) than in 2022 (28.89 and 26.11%), respectively . Age of tree, cropping system, disease status and management, yield, and weed showed highly significant ( P < 0.0001) associations with powdery mildew and anthracnose severity. Likewise, altitude, production year, survey site, and relative humidity were significantly ( P < 0.0001–0.05) associated with anthracnose severity in both single and multiple reduced variable models. In the model, precipitation was highly significant ( P < 0.0001) in association with powdery mildew severity than anthracnose. Aged trees, monocropping, disease, and weed management, along with favorable environmental conditions, were highly contributing factors to the high (> 26% for powdery mildew and > 24% for anthracnose) disease severity in the model. Conversely, recently established orchards (≤ 5 years), mixed crops with legumes, and pruning with appropriate sanitation applied as disease management practices contributed to low (< 26% for powdery mildew and < 24% for anthracnose) disease severity. In conclusion, the current study indicated that powdery mildew and anthracnose diseases were major constraints on apple production, and their epidemic development was significantly influenced by biophysical factors. Hence, the findings may provide a basis for developing powdery mildew and anthracnose sustainable management strategies, which would ensure apple production in the study areas and in agro-ecologies of a similar kind elsewhere. Thus, following intercropping and/or mixed cropping and proper disease and weed management, along with other good agronomic practices, is suggested to manage the two diseases in the area and other related agroecologies.