From the Field – Experimental design of trials for grape berry moth on slope vineyards in the Douro Wine Region

The moth Lobesia botrana (Denis & Schiffermüller, 1775) (Lepidoptera: Tortricidae) is the major pest of grapes (Vitis vinifera L.) in southern Europe, including in Portugal, specifically in Douro Wine Region (DWR). Effective control of this pest is required, due to the great economic impact on grape production and wine quality. Indeed, the DWR is unique offering different microclimates, due to its rugged orography and the steep slopes.

Trials under the NOVATERRA project are being carried out at vineyards in Quinta do Seixo (property of SOGRAPE, a member of NOVATERRA consortium), where vineyards with different topography (vertical-row planting, 1-row or 2-row terraces) and at different altitudes and slope aspects are subjects of study.

Vineyards with different systems and at different altitudes and slope aspects are subject to study under the NOVATERRA project in Quinta do Seixo.

A member of NOVATERRA consortium, CORTEVATM developed a novel method of pheromone (E,Z-7,9-dodecadienyl acetate) application (natural degradable gel without micro-plastics and solvents – Enrapta Lobesia Press) against the grape berry moth, L. botrana, to be applied on the grapevine’s bark. The experimental design developed by SOGRAPE (see the below picture) consisted of applying this gel with about 500 to 600 drops per hectare. The trial also included control untreated vineyards and vineyards treated with the conventional product for mating disruption (MD). The areas enclosed by the white line in each zone represented about 2 hectares, which were used for observation and monitoring of L. botrana and evaluation of product effectiveness.

Given the product’s behavior, by generation of a pheromone cloud to confuse insects, there are specific challenges for using it in slope vineyards. For example, the stability of the pheromone cloud on the target site depends on wind direction and speed.

Additionally, insect pressure is promoted by local temperature and relative humidity, as well as by refuge in nearby unprotected vineyards or other host plants for the target species. In the case of terraced vineyards, slope convexities created by water lines are areas of greater pressure that alternate, in the same row of vines, with concavities.

Finally, in vertical row vineyards, costs of manual application increase because of inherent morosity in climbing slopes that may exceed 40%. Considering all of these factors for the experimental design, an approach derived from medical epidemiology was applied, using areas for each modality larger than the observation area to simultaneously obtain adequate buffering between adjacent modalities and confound a large number of different situations for all modalities to control only the most relevant variables, in this case, the application form of pheromone, altitude and slope aspect.

Experimental design of the trial. Red: untreated; Purple: conventional product; Green: 500 drops per hectare with Enrapta Lobesia Press; Yellow: 600 drops per hectare with Enrapta Lobesia Press; White line: areas for observation and monitoring of the L. botrana.