Reduced fungicide sprayings: A biodiversity boost?

Abstract

Pesticides are considered one of the main causes for arthropod decline in agriculture which in turn may affect ecosystem services such as natural pest control and soil fertility. Although insecticides are usually most harmful to non-target organisms, also fungicides can have unintended side effects on arthropods. Grapevine typically receives ten fungicide sprayings in three months of growing season in the Palatinate region, Germany. Sprayings contain several plant protection products of varying toxicity towards non-target organisms in both organic and conventional viticulture. However, fungus-resistant grape varieties allow to study substantial reductions in fungicide applications under realistic conditions.

We compared the effects of reduced fungicide applications across 36 vineyards in a 2×2 factorial design, including fungus-resistant and susceptible grape varieties under organic and conventional management. Our sampling included arthropods from the grapevine canopy and the inter-row vegetation as well as soil dwelling arthropods and soil fungal communities. Additionally, we set up camera surveyed sentinel cards to identify predators of the European grapevine moth (Lobesia botrana).

First results indicate that canopy dwelling arthropods were strongly enhanced by reducing fungicide sprayings, particularly predatory arthropods including spiders. However, these effects were less pronounced in the inter-row vegetation and on the soil. Both organic management and fungus-resistant grape varieties influenced arthropod communities, but to different extents depending on the sampled microhabitat.

These preliminary results indicate declining effects of fungicides on non-target arthropods from the grapevine canopy (to which the fungicides are applied) towards the ground. The cultivation of fungus-resistant varieties represents a crucial step in the pursuit of sustainable viticulture.