Reducing chemical inputs for sustainable protection of strawberry

In Trentino region strawberries (Fragaria x ananassa) are grown under tunnel with soilless cultivation system. This growing method allows to reduce grey mould (Botrytis cinerea) incidence but creates conditions for powdery mildew (Podosphaera aphanis) development. Starting from 2013, experimental trials with the aim to reduce chemical treatments on strawberry have been carried out. Some fungicides authorized in organic production have been recently registered on strawberry in Italy: among them there are commercial products based on potassium bicarbonate with specific activity against powdery mildew and very short pre-harvest intervals, moreover they are exempt from MRL. Semi-field and field trials were carried out to evaluate the efficacy of potassium bicarbonate against powdery mildew on strawberry. In the semi-field trials, potted plants were kept in a glasshouse and inoculated by shaking infected leaves over the plants. Treatments were: potassium bicarbonate, sulphur, bupirimate and untreated control. Four and five weekly applications were applied in the first and second trial, respectively. In the field trial (tunnel and soilless cultivation) a conventional spray program was compared with bicarbonate applications and the untreated control. Incidence and severity on leaves and fruits were assessed in these trials. In the glasshouse trials, the spray applications with potassium bicarbonate significantly reduced the incidence and severity of powdery mildew compared with untreated control. Efficacy of bicarbonate was similar to sulphur but was lower compared with the chemical reference. In the field trial, the untreated plots showed a high incidence of the disease while a very low incidence was observed both in conventional and bicarbonate treatments. In conclusion, our results showed that repeated applications of potassium bicarbonate were effective against powdery mildew and no phytotoxic effects were observed. Therefore this active ingredient can be included in IPM programs of strawberry, allowing a reduction of pesticide residue

Experimental trials to control strawberry powdery mildew in Italy

Powdery mildew (Podosphaera aphanis) is the main pathogen of strawberry (Fragaria x ananassa) grown under high tunnels and can infect all the aerial parts of the plant. Increasing restrictions on the use of chemical fungicides make necessary to develop new technologies and to evaluate the efficacy of alternative substances such as natural, microbial or low-impact products. Starting from 2013, greenhouse and field trials have been carried out in Trentino region (Northeastern Italy) to evaluate the efficacy of alternatives to chemical fungicides on strawberry. Their integration into strategies against powdery mildew was also tested. On the June-bearing cultivar Elsanta, repeated applications of products based on potassium bicarbonate and orange essential oil showed a good efficacy against powdery mildew, both in field and in semi-field trials. Other substances such as vegetal extracts, whey and fertilizers were not sufficiently effective in controlling P. aphanis. Everbearing varieties, given the long production cycle and susceptibility, showed greater problems in containing the disease. Further trials, integrating different agronomical and disease management practices, will be necessary to achieve an effective control of powdery mildew on these cultivar

Apiognomonia erythrostoma: an emerging disease of stone fruits in Italy

Apiognomonia erythrostoma is a fungal pathogen of stone fruits known as the causal agent of cherry leaf scorch. In the Emilia-Romagna region the disease has been reported since 2001 on apricot, and severe infections have been recorded on sweet cherry trees since 2013. In 2015, symptoms resembling those made by A. erythrostoma were observed on sweet cherry in a mountainous area in the Trentino region. Symptoms on the leaves start with pale green spots that turn yellow and red, while affected areas become necrotic and the leaves dry up, remaining attached to the tree. Irregular red areas appear on the fruit, causing deformity and cracks. In Emilia-Romagna, a preliminary epidemiological study on apricot was carried out in the field over three years, with the aim of determining infection events. Dead, overwintered leaves containing fruiting bodies of A. erythrostoma were collected from apricot trees and investigated for ascospore maturation. Maturation and release of ascospores was correlated with degree days and compared with infections in the field. This preliminary investigation provided information about the first, maximum peak and end of ascospore release. Monitoring of the presence of the disease in Emilia-Romagna and Trentino was carried out in the main apricot and cherry growing areas. Typical symptoms on leaves, fruit and the reproductive structures of A. erythrostoma were found both in orchards and on wild cherry trees in the surrounding areas, suggesting that infected uncultivated trees may act as an inoculum source for the pathogen. In 2016, preliminary epidemiological studies of perithecial maturation, ascospore release and symptom development on potted plants were also carried out in Trentino. Potted cherry plants were exposed to ascospore infection from infected cherry leaf litter. Ascospore release was monitored by means of a volumetric spore trap placed over the leaf litter. Potted cherry plants were exposed and replaced weekly with healthy ones. The first ascospores were detected by the spore trap during the first ten days of April, with a peak at the end of May, in conjunction with rain. Symptoms on leaves appeared four to six weeks after the infection event. Further studies will be necessary to fully understand the biology and the epidemiology of this fungus in northern Italy, in order to implement an effective control strateg