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Quinone outside inhibitor fungicides are synthetic derivatives of naturally occurring strobillurin compounds introduced in the late 1990s and represent a novel group of fungicides, highly active against a broad range of fungi belonging to Oomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes. They are mitochondrial respiration inhibitors (MRI) which inhibit fungal respiration at the Quinone “Outside” (Qo) binding site of the cytochrome bc 1 complex. Being site-specific, they are at risk from the development of resistance in the target plant pathogens.

Grape is attacked by a number of diseases. However, anthracnose, downy mildew, powdery mildew, and bunch rot/ berry rot caused by certain fungi or group of fungi are most important. Their control lies in modifying vine microclimate; timely annual pruning of dead arms/vines, and also removal of abnormal un-harvested bunches from the vines immediately after harvest is over, and timely and judicious application of fungicides, after annual pruning and during the season.

Strobilurins are a group of chemical compounds used in agriculture as fungicides. They are part of the larger group of QoI inhibitors, which act to inhibit the respiratory chain at the level of Complex III.

Some common Strobilurins are azoxystrobin, kresoxim-methyl, picoxystrobin, fluoxastrobin, oryzastrobin, dimoxystrobin, pyraclostrobin and trifloxystrobin.

Strobilurins represented a major development in fungus-based fungicides. They were extracted from the fungus Strobilurus tenacellus. They have a suppressive effect on other fungi, reducing competition for nutrients; they inhibit electron transfer in mitochondria, disrupting energy metabolism and preventing growth of the target fungi.