S14 - Session O4 - UVC treatment effective against powdery mildew in zucchini

Authors: Jonathan De Mey *, Sabien Pollet

Powdery mildew fungi are particularly sensitive to UV light and these fungi cannot rely on their recover mechanisms in the absence of blue light at night. The first successes within a crop protection context have been achieved under sheltered conditions for crops such as strawberry, lettuce, tomato and cucumber. UV treatment seems an interesting control method within an IPM context as it can lead to a reduced use of chemical crop protection. In two trials in open air zucchini, a UV treatment evaluated. For this, UV lamps were mounted on a self-propelled spraying tractor. The UV apparatus exists of four light armatures containing a UVC lamp (type Philips TUV PL-L 95W). An electrical power unit (petrol powered) with AC output provides power. Side screens protect bystanders against direct radiation and a remote control (Niko RF system) is installed to switch on the lamps from within the tractor cabin. In the first trial the concept was evaluated. Subsequently, the second trial was designed as a randomized complete block trial to study the effectivity against powdery mildew. On July 19, the cultivar Milos was planted. Net plot size was seven plants and sufficient discard area was maintained between experimental plots. UV treatments were performed after sundown every three days from Aug 17 to Sep 24. The trial consisted out of six objects: untreated, high dose (3X), medium dose (1.5X), low dose (X), mixed organic and a chemical reference (with X = 72 J.m - ² from Aug 17 to Sep 9 and X = 216 J.m - ² from Sep 10 to Sep 24). UV treatment at high and medium dose showed a clear efficacy in comparison with the untreated (resp. 63% and 37% on Sep 29, upper side of leaves) in the trial and had no apparent adverse effect on the crop.