Project Status & Results - Apple Trials
Apple field trials have taken place on farms in Italy and Spain for 2020. In Italy, 2 varieties of apple were targeted: ‘Gala’ and ‘Jeromine’, both being grown on the same farm. In Spain the variety was ‘Gala'. As with strawberries, plant pathogens and arthropods were monitored at regular intervals throughout the fruit growing seasons, identifying diseases and pest outbreaks. Within the CleanFruit strategy test plots, the growers were provided with advice and appropriate biological control products from Koppert.
The control plots in Italy differed from each other: for ‘Gala’ this was an organic treatment, and for ‘Jeromine’ this was a conventional plot, using mainly a variety of chemical applications alongside some pheromone attractants and soil bacteria treatments.
The organic control treatment was very similar to the CleanFruit treatment. The main differences were use of a green slurry and the soil bacterium Bacillus thuringiensis, which were used in the organic but not in the zero-residue treatments, and for the CleanFruit zero residue treatment the nematode Steinernema feltiae was included.
The main issues for apples were incidences of fireblight (Erwinia amylovora), apple scab caused by the fungus Venturia inaequalis, and presence of several species of aphid, including Rosy apple aphid (Dysaphis plantaginea), apple aphid (Aphis pomi), and woolly apple aphid (Eriosoma lanigerum).
In addition, spotting on leaves caused by Alternaria spp. fungi were found, plus fruit rots caused by Monilia spp. infection, and occurrences of codling moth (Cydia pomonella).
Throughout the season, the pathogens and pests were assessed 2-3 times in both organic/conventional and the CleanFruit zero-residue plots, and in most cases no significant differences were found, the CleanFruit biological treatments being equally as effective as the conventional chemical or organic treatments. Some differences were found on one farm, with fewer incidences of Alternaria leaf spotting on ‘Gala’ apples within the CleanFruit treatment than in the conventional organic treatment plots. In general, during the trial, there was a low incidence of the key apple pathogens (Venturia inaequalis, powdery mildew) on the zero-residue plots. Codling moth was well managed with sexual confusion and granulosis virus. Furthermore, Eriosoma lanigerum was naturally parasitized by Aphelinus mali.
Post-harvest quality of the ‘Gala’ fruits showed no significant differences between the two treatments regarding weight, size, shape, sugar levels and acidity. There was a significant difference between the two treatments about firmness, with the CleanFruit apples being firmer than the organic fruits. There were no significant differences between the treatments for the ‘Jeromine’ apples.
Apples were also tested for chemical residues. For ‘Gala’ apples, all conformed to the required tests for residue levels, both in the organic and the CleanFruit treatments. The analysis of the residues on 'Jeromine’ apples, showed the presence of captan residues as the only active ingredient found. Next year new pesticides will have to be adopted to replace it. Possible prospects for next year will be the use of half the dose for some plant protection products; the adoption of chemical control until full bloom and of biological control from mid to late season with copper, sulphur, sodium bicarbonate and neem based products.
Any differences and issues will be investigated further in 2021, with alternative treatments identified where needed.
Having seen few differences between the treatments, and therefore the results for the ‘Gala’ apples, in 2021 comparisons will be made with a conventional crop protection strategy.