The Effect of Paraffin Oil Spraying and Powdery Mildew Infection on Leaf Gas Exchange and Yield of Chardonnay and Kékfrankos (Vitis vinifera L.) in Hungary

Abstract

Various oils can efficiently control a wide range of pests and pathogens on plants. In this study, we tested the effectiveness solely applied paraffin oil (PFO) spraying against Erysiphe necator, the causal agent of grape powdery mildew (GPM). Its effects on gas exchange and yield at harvest were also investigated. Experiments were conducted in Eger between 2013 and 2014 with two cultivars (Kékfrankos and Chardonnay) showing differing susceptibility to GPM. Treatments with 2.2 and 3.3 v/v% PFO spraying inhibited GPM; however, this effect was influenced by the individual resilience of the variety and the infection pressure of the vintage. The PFO treatment caused decreased leaf gas exchange parameters compared to conventional treatment. The berry yield was also lower in PFO-treated parcels, although yield may be affected by numerous factors and requires further investigation. The mineral oils may have a phytotoxic effect on the grapevine through impairment of the photosynthetic performance, although this effect cannot be connected to a particular PFO concentration according to our research results. This negative effect of PFO highly depends on the ampelographic characteristics of the examined cultivars and vintage. In addition, the physical properties of the spraying agent may also play an important role.