Detection of latent infections caused by Colletotrichum sp in olive fruit

Aims: To set up a practical method to detect latent infections of Colletotrichum sp., the causal agent of olive anthracnose, on olives before the onset of disease symptoms. Methods and Results: Freezing, sodium hydroxide (NaOH), ethanol and ethylene treatments were evaluated to detect latent infections on inoculated and naturally infected olive fruit by Colletotrichum sp. as non-hazardous alternatives to paraquat. Treatments were conducted using fruit of cultivars Arbequina and Hojiblanca. The disease incidence and T-50 were calculated. Dipping in NaOH 0.05% solution and the paraquat method were the most effective treatments on both inoculated and naturally infected fruit, although the value of T-50 was lower for the NaOH method than for the paraquat method in one of the experiments. Subsequently, the dipping time in NaOH 0.05% was evaluated. Longer dipping times in NaOH 0.05% were better than shorter ones in cultivar Arbequina, with 72 h being the most effective in cultivar Hojiblanca. Conclusions: NaOH solution is a practical method to detect latent infections of Colletotrichum sp. on immature olive fruit. Significance and Impact of the Study: This study is relevant because we set up a viable, non-hazardous alternative to paraquat to detect latent infections of Colletotrichum sp. using NaOH. The use of NaOH is a simple and eco-friendly tool that allows the determination of the level of latent infections by Colletotrichum in olives. Therefore, our method will be useful in decision-making processes for disease management before the appearance of the first visible symptoms.