Stefano Demarchi

Nursery treatments with non-conventional products against crown and root rot, caused by Phytophthora capsici, on zucchini

Phytophthora capsici, a pathogen causing crown and root rot of zucchini in southern Italy since the 1980s, has recently been observed in open field in northern Italy, causing severe losses. Since chemical control on zucchini is complicated by a limited availability of registered chemicals, as well as by the scalar harvest, a number of resistance inducers, organic amendments, biocontrol agents and fungicides were tested against P. capsici, under greenhouse conditions. Experiments were carried out at the nursery level, with different timing and number of applications. In the presence of a very high disease pressure, the best disease control was provided by mefenoxam, followed by the phosphite-based products, which acted as resistance inducers and also provided a positive effect on plant biomass. Acibenzolar-S-methyl, although effective, was sometimes phytotoxic. The biocontrol agents tested as well as the patented formulation of Brassica carinata defatted seed meals were not effective, providing results statistically similar to the untreated control. The efficacy of resistance inducers is interesting in view of their possible use in alternation with chemicals, or as stand-alone treatments in cultivation systems which do not adopt chemical control.

Seed dressing to control downy mildew of basil

Four experimental trials were carried out in order to evaluate the efficacy of different products (chemicals, resistance inducers and natural products) as well as heat air when applied to basil seeds naturally infested by Peronospora belbahrii, the causal agent of downy mildew of basil, a pathogen which is seed transmitted. Seed quality, as vigour index, was also evaluated. In general, seed treatment had a positive effect on the reduction of disease incidence and on plant biomass at the end of each trial, with very satisfactory results when disease incidence was lower than 10% and still satisfactory results with a higher disease incidence. Although many of the fungicides, resistance inducers and thyme oil treatments tested showed a significant disease reduction compared with the untreated control, the protection offered was only partial. Moreover, the effectiveness of the tested seed treatments varied considerably between the trials. The seeds treatment with heat air (65°C for 10 min) significantly reduced the number of infected plants per container. The interaction effect between the fungicides (at the lowest dosage tested, with the exception of acibenzolar-S-methyl, and dimethomorph), thyme oil and the heat air treatment was also significant. In terms of biomass, most treatments not significantly improved the fresh weight in comparison with the untreated control. The highest biomass was observed in the plots where seeds were dressed with mancozeb combined with heat air. Interestingly, thiram is also effective against other pathogens affecting basil and the thermal treatment and potassium phosphite are fully compatible with the rules of organic farming. Seed dressing represents the starting point of a full integrated approach for downy mildew management.