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Strawberry field trials have taken place in polytunnels on 2 farms in Italy for 2020. Plant pathogens and arthropods were monitored at regular intervals throughout the fruit growing season, identifying diseases and pest outbreaks. Within the CleanFruit strategy test plots the growers were provided with advice and appropriate biological control products from Koppert. Control polytunnels were also in place, where fruit was grown using conventional methods.

The two farms were 8 km apart, growing the same variety (‘Premy’) of strawberry. There were some differences in their growing conditions:

  • Plants 25 cm apart in a 50 m-long tunnel for one, 30 cm apart in a 80 m long tunnel for the other;
  • Differences in effectiveness of plant residue removal in the spring;
  • Fertigation differences, with one applying only irrigation, and the other including some fertiliser with the irrigation;
  • Differences in attitude towards the residues as they had different market channels – wholesaler vs direct sale

Assessments on strawberries in both control and CleanFruit plots found issues with Botrytis cinerea, Cladosporium spp., Fusarium avenaceum, and Alternaria spp.

Throughout the treatment, the pathogens were assessed 2-3 times in both conventional and CleanFruit plots, and in most cases, no significant differences were found – i.e. the CleanFruit biological treatments were just as effective as the conventional chemical treatments. Some differences were found on one farm, with more Botrytis cinerea and powdery mildew present in the CleanFruit plots.

Post-harvest quality of the fruits showed no significant differences in either farm between the two treatments, with weight, fruit firmness, sugar, acidity and colour. One farm showed a difference in storage quality of the fruit, with the CleanFruit strawberries having a higher incidence of fruit rot and grey mould than those from the conventional plot.

The overall conclusion is that the zero-residue strategy has no impact on the quality of the strawberries. The high incidence of grey mould may be limited by applying good agronomic practices to limit its spread. The spread of powdery mildew can be limited by sulphur or sodium bicarbonate treatments and by increasing the distance between plants. Aphids have been controlled thanks to beneficial insects applied during the season. Regarding spider mite, a careful monitoring of the population is recommended throughout the season and acaricide treatments should be avoided approaching harvest time.

Strawberry purees and powders were also tested and showed that the strategy, CleanFruit or conventional, had no impact on the sensory quality of strawberries. Strawberries obtained from both farms are a little different to each other, with higher sugars, acidity, taste intensity and sweetness in one farm, potentially reflecting a slightly higher degree of ripeness. This difference disappears after spray drying.

Strawberries were tested for chemical residues. None of the samples strictly meets the target of zero residue.

  • We are almost there with the CleanFruit plot sample from one farm.
  • Both CleanFruit samples look better than the conventional ones
  • We have a problem of Fosetyl Aluminium almost everywhere
  • We observed various individual pesticide traces, especially in conventional samples in both farms, that may be representative of applied pesticides.

These differences and issues will be investigated further in 2021, with alternative treatments identified.

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