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Ethephon was applied at 0, 625, 1250, 1875, and 2500 m·gliter-1 in 2 consecutive years to `Arbequina' olive trees to determine its effect on fruit removal with mechanical harvesting and on fruit oil composition. Ethephon increased the mechanical harvesting efficiency by 20%. Ethephon at 1250 and 1875 mg·liter-1 were the optimum treatments, resulting in 63% and 66% of the olives being mechanically harvested, respectively, with a preharvest olive drop of 10% and 11%. Leaf drop (4.6 and 4.8 kg/tree fresh weight, respectively) at these concentrations did not reduce flowering the following year. Oil acidity, peroxide value, and fatty acid composition were affected little by ethephon and the values observed were within the range of normal annual variation. These results suggest that ethephon did not modify oil quality and that its use on traditionally pruned `Arbequina' trees is not economically justifiable. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
In a 3-year experiment in two drip-irrigated orchards on the Mediterranean coast, boron (B) sprays applied at rates of 0.6 and 1.2 g per tree and a soil B application of 12 g per tree did not increase fruit set or production of Corylus avellana L. `Negret' and `Pauetet' hazelnuts with mid to low foliar B levels (14.3 to 21.8 μg·g-1 dry mass). The average fruit set and nut yields of the trials were, respectively, 66% and 3.54 kg per tree for `Pauetet', and 50% and 4.54 kg per tree for `Negret'. The lack of response to B applications might be due to 1) initial fruit set levels were high; 2) the current B recommendation guidelines (25 to 30 μg·g-1 dry mass) might be adequate for fruit set and yield; 3) the rates of B applied might be too low; and 4) weather and soil conditions, cultivars, and biennial bearing may have masked any response to foliar B application.