Drosophila Suzuki is worrying again

[vc_row full_screen_section_height=”no”][vc_column][vc_column_text]For this reason, it is necessary that next year Italy does not find itself unprepared as has happened in some areas this year where significant quantities of grapes were lost due to sudden rot during harvest time, attributable precisely to the Asian insect.

If, in fact, in 2015 the hot and dry year decimated the population, they do not create problems, in 2016 the situation has become critical. The autumn of 2015 and the mild winter have allowed the population to proliferate, appearing even in those areas where it was not there before, such as Montalcino, and favoring a descent towards the south of the DS, recorded for the first time in Trentino in 2009.

The insect prefers red berries with thin skin. At risk are therefore the varieties with thin skin, such as Schiava, but also all the other grapes close to ripening, when the berry is most turgid.

To prevent the DS from taking over the harvest, it is worth keeping an eye on the grapes in advance starting from veraison. Monitoring wild plants that ripen earlier nearby – for example elderberry but also cherry or crops such as blueberries, which the insect is fond of – can act as a spy and alert on a possible development of the population, thus allowing you to take action in time to protect the grapes.

For now, integrated pest management is still in the experimental phase, although with good results. Already in 2012, the Mach Foundation, in collaboration with the Mediterranean Agronomic Institute of Bari (IAMB) and Oregon State University (OSU), had identified the Pachycrepoideus vindemiæ which were joined, the following year, by two other species with promising efficacy: the Leptopilin heterotoma , Trichopria drosophilaAll three species of parasitoid, small wasps, are able to attack DS by laying their eggs inside the juvenile stages of the midge.

In France, producers have tried covering the grapes with a solution of sulfur and citric acid or clay because the females do not lay eggs on dusty berries.
For those who do mechanical harvesting, the advice is to empty the juice from the crate. Carrying out fermentations in an open vat also helps to eliminate any acetic acid that may have formed.

The following are the conclusions of a joint Italian-American study published in the Journal of Entomological Economics, which compared the Italian research, carried out in the province of Trento, and the other in the Willamette Valley of Oregon, both carried out between the 2011 and 2013 grape harvests.

For the entire experiment we refer to:
http://www.vignaecantina.it/drosophila-suzuki-cosa-emerge-dal-confronto-fra-uno-studio-italiano-e-uno-americano.html

The results of the experiments suggest that DS egg deposition increases from veraison to harvest with the highest infestation rates occurring just before and during harvest. This infestation rate corresponds to a decrease in resistance to bunch penetration during the same period. Another trend emerged, that more eggs are laid on bunches with higher Brix levels.

It was also found that the structural integrity of the grape skin influences the deposition of eggs by DS. If the bunches used for the experiment were perfectly intact, the number of eggs present was very low. On the contrary, if the grapes were damaged in some way, the number of eggs present was significantly higher. This indicates that having already damaged bunches is a possible vector in the increase rates of DS infestation in the vineyard.

In addition to the above, the consistency of the berry skin, measured by penetration resistance, significantly influences the egg deposition rates on the berries. In detail, it was found that the berries with a penetration resistance level higher than 40cN remained mostly unharmed.

For further information on the status of research and means of detection: http://www.bioattualita.ch/it/coltura/frutticoltura/protezione-piante/drosophila-suzukii.html[/ Vc_column_text] [/ vc_column] [/ vc_row]