Grapes are susceptible to fungal diseases (eg. Botrytis cinerea (gray mold), Plasmopara viticola (downy mildew), Uncinula necator (powdery mildew), Elsinoë ampelina (anthracnose), and Guignardia bidwellii (black rot)) and in some cases the fungi produce mycotoxins (eg. ochratoxins produced by mycotoxigenic fungi such as Aspergillus carbonarius).
You could find more about grape diseases and their management in the following video:
You could find how grape Downy Mildew develops in the following video:
You could find about grape Powdery Mildew management in the following video:
You could read more about mycotoxins in wine here: https://www.researchgate.net/publication/227820737_Occurrence_of_ochratoxin_A_in_Greek_wines
You could read EFSA’s statement regarding Ochratoxin A (OTA) toxicity here: https://www.efsa.europa.eu/en/efsajournal/pub/1626
Grape producers apply fungicides (usually of chemical origin) in vineyards in order to protect vines and grapes from fungal diseases and their effects in productivity and quality.
According to recent findings, the new generation of fungicides can be transferred in musts and wines, due to their physicochemical characteristics (Esteve-Turrillas et al. 2016).
Chemical plant protection is the use of a wide range of chemical substances for the purpose of killing, obstructing, or merely slowing the growth of phytopathogens. Pesticide formulations are economical, effective, and in some cases are the only ones satisfactory control method.
Formulations used to combat disease of plants caused by fungi are called fungicides. Though the term etymologically means that the pesticide kills the fungus, it is also used in the case of chemicals substances that simply hinder or slowing the growth of fungi.
They are distinguished in protectors (or contact fungicides), which only protect the part of the plant in which they have been deposited, and systemic, which are received by the plant and move into the plant body.
What is “residue”?
The traces pesticides leave in treated products are called “residues” (https://ec.europa.eu/food/plant/pesticides/max_residue_levels_en)
Cabras, P., & Conte, E. (2001). Pesticide residues in grapes and wine in Italy. Food Additives & Contaminants, 18(10), 880–885.
Esteve-Turrillas, F. A., Agulló, C., Abad-Somovilla, A., Mercader, J. V., & Abad-Fuentes, A. (2016). Fungicide multiresidue monitoring in international wines by immunoassays. Food chemistry, 196, 1279-1286.