Arthropods on grapes benefit more from fungicide reduction than from organic farming

BACKGROUND

Pesticides are considered main contributors to global arthropod declines and therefore may decrease the provision of ecosystem services such as natural pest control. Organic farming and cultivating pest- and disease-resistant varieties can allow pesticide applications and their impacts on nontarget organisms and the environment to be reduced. We investigated the effects of organic versus conventional management and fungus-resistant versus susceptible wine grape varieties on arthropod biodiversity and pest control of grape berry moths in 32 vineyards in the Palatinate region, Germany. Hazard quotients of applied pesticides were calculated for each vineyard.

RESULTS

The cultivation of fungus-resistant varieties led to significantly reduced hazard quotients and in turn enhanced abundances of natural enemies, particularly theridiid and philodromid spiders. Unexpectedly, organic management resulted in higher hazard quotients than conventional management and reduced numbers of natural enemies, particularly earwigs. Pest predation rates showed no significant differences between grape varieties or management types.

CONCLUSION

Widespread benefits of organic management on arthropod biodiversity found in other crops were absent in our viticultural study region. This is likely due to the dominant role of fungal diseases in viticulture, which requires high numbers of fungicide treatments under both conventional and organic viticulture. Thus, fungicide reduction through the cultivation of fungus-resistant grape varieties is one key element to fostering the abundance of arthropods in general and beneficial arthropods in particular. Beyond vineyards, this is potentially relevant in numerous other crop types. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.