Studies of Foliar Applied Clay Effects on the Apple Fruit Quality

Fruit quality fulfillment is a permanent concern of the researchers and fruit growers. Various formulations and substances have been tested to reach this important goal, particularly regarding russeting and sunburn protection. Investigations concerning the preventative application of kaolin and bentonite suspensions, as well as a new binary formulation kaolin-fungicide and a new polyfunctional formulation (Carbosulf, non-commercial product), against russeting and sunburn were carried out between 2000 and 2002 in Romanian locations: RIFG Maracineni - Pitesti and RSFG Targu Mures. The trial was conducted in a Goldspur (grafted on M 26) bearing apple orchard, using Promalin and water (non treated plot) as control. The treatments were applied four times between June and September, beginning at flowering and continuing at 14 day intervals for three treatments; Carbosulf was instead sprayed three times before harvest at a 0.5% concentration. The foliar clays application increased the percentage of russeting free fruit from 17% (controls) to 23-28%. Carbosulf performed better than the clays (average 38% fruits russeting free), but worse than Promalin, which averaged close to 59% russeted free fruits. Kaolin treatments reduced significantly the losses in sunburned fruits from 24-28% in the controls to 12-15%. Because the tested products are containing only ecological components, their application may be extended to the organic crops protection, even though the results seem to be moderate in strength.