Anthracnose, caused by Colletotrichum spp., is the main olive fruit disease. Colletotrichum can severely infect olive fruit with a negative impact on the oil quality. However, the relationship between visible infections of Colletotrichum spp. and olive oil quality is unclear and the influence of latent infections is unknown. This study considers Colletotrichum spp. latent infections and visible infections as factors affecting the quality of olive oil. IAbsorbance in UV (K232 and K270), free acidity, and peroxide index were evaluated in oils from fruit with latent and symptomatic infections by Colletotrichum godetiae of the cvs. Arbequina, Hojiblanca, and Picual. Olive oil samples from i) latent infected fruit at three maturity stages and after two incubation periods and from ii) sets of oils from mixtures of healthy and infected symptomatic fruit were used to determine the impact of the disease on oil quality. Oils from latent infected fruit of cv. Arbequina showed higher acidity than control oils (P = 0.012). Linear and exponential models were fitted to relate the oil quality parameters to the proportion of symptomatic fruit. Acidity was the most affected parameter, mainly in oils from cv. Arbequina. The thresholds of the percentage of affected fruits causing the loss of category in the quality of the oil varied greatly according to cultivar, with ‘Arbequina’ being the most sensitive.

Red leaf blotch (RLB) disease of almond, caused by Polystigma amygdalinum, is an important foliar disease in most production regions of the Mediterranean basin and the Middle East because severe infections may cause a premature defoliation of the tree. Some key aspects on the epidemiology of P. amygdalinum were studied in multiyear trials in two almond-growing regions in Spain, which included the seasonal development of perithecia and production and germination of ascospores along with the disease incubation and plant infectivity periods. Our results showed that primary inoculum was available in extended periods (January to August). Significant differences in ascospore amounts among regions, higher in the southern Andalusia and lower in the northern Catalonia, and years of study were detected. The factors geographical location, sampling period, and evaluation year were found significant on the development of P. amygdalinum perithecia. Variable ascospore germination rates were observed from April to July: >15% but rarely exceeding 30%. The RLB infectivity period in Catalonia extended from March to mid-June, whereas in Andalusia it was from March to May. The incubation period was mainly in a range of 5 to 10 weeks in Catalonia. The environmental conditions of October to January influence the available ascospore amounts in the next season. RLB infection occurs in spring to summer when mean temperatures are in the range 10 to 20°C. These results represent the first step in developing a prediction model of the disease that might serve as a tool for the control of RLB.

Cercospora leaf spot of olive (CLSO), caused by Pseudocercospora cladosporioides, is one of the most important foliar diseases of olives worldwide. This study aimed to evaluate the effect of a wide range of fungicides on mycelial growth and conidial germination of P. cladosporioides in vitro, and to evaluate the effect of several fungicides, application timings and management strategies (conservative and risky) to control CLSO under field conditions. Of the studied fungicides, strobilurin compounds and benomyl were the most effective active ingredients, followed by folpet, captan and maneb, in inhibiting mycelial growth and conidial germination. The pyraclostrobin + boscalid treatment was effective under field conditions, even without the application of supplementary copper. Treatments conducted in October or March were more effective than those conducted in May. Management strategies based on the author’s experience reduced copper applications up to 32.0% and 50.0% (conservative and risky strategy, respectively) in comparison to the reduction with the traditional strategy, without increasing CLSO incidence. This work provides useful information about effective formulations against CLSO and a reduction in unnecessary fungicide applications in an effort to implement IPM in olive orchards under Mediterranean conditions.

Developing models to understand disease dynamics and predict the risk of disease outbreaks to facilitate decision making is an integral component of plant disease management. However, these models have not yet been developed for one of the most damaging diseases in Mediterranean olive-growing areas (verticillium wilt (VW), caused by the fungus Verticillium dahliae Kleb.), although there are parameters (e.g., level of V. dahliae inoculum in the soil, level of susceptibility of the olive cultivar, isothermality, coefficient of variation of seasonal precipitation, etc.) that have previously been correlated with the severity of the disease. Using the data from previous VW studies conducted in the Guadalquivir Valley of Andalusia (one of the most damaged areas worldwide), in this work, a set of fuzzy logic (FL) models is developed with the aforementioned disease and climatic parameters, and the results are compared with machine learning (ML) models, of known effectiveness, to predict the risk levels of VW appearance in an olive orchard. Under these conditions, both groups of models were less effective than those previously studied with simpler models or models used under controlled conditions. However, the accuracy achieved with the most efficient FL model (60%; classification system based on fuzzy rules using the Ishibuchi method with a weighting factor) was somewhat greater than the efficiency achieved with the most efficient ML model (59.0%; decision tree classifier), in addition to being more appropriate (from a practical point of view) for the incorporation into a decision support system by allowing the risk of appearance of each observation to be known by providing rules for each of the combinations of the different parameters with similar precision. Therefore, in this study, we propose the FL methodology as suitable to act as an expert system for the future creation of a decision support system for VW in olives.

Southern blight caused by the soil-borne fungus Sclerotium rolfsii is one of the most important diseases of vegetable crops, including potato (Solanum tuberosum), causing great economic losses in warm humid regions (Mullen 2001; Fiers et al. 2012). In 2015, potato tubers collected from several orchards located in Sevilla province (southern Spain) showed soft rot symptoms after storing in warehouse. Symptomatic tubers were incubated in humid chamber at 25ºC and 100% relative humidity. Affected tuber sections were cut washed, surface-disinfested in a 1.5% sodium hypochlorite solution. Small pieces of soft tissues were plated onto potato-dextrose-agar (PDA). Dishes were incubated at 25ºC in the dark and fungal colonies were transferred to PDA. White hyaline septate mycelium was observed on the surface of incubated tubers and on PDA. Light to dark brown sclerotia of diameter 1 to 2 mm developed from the mycelium. According to morphological characteristics (shape, size, color, presence of septum septated scler...