PFA CONTROL IN 'SERR' IN CHILE

Walnut varieties to various degrees present pistillate flowers abortion (PFA), due to an excess of pollen that generates ethylene, causing abscission layer formation and organ excision. ‘Serr’ is one of the most affected walnut varieties by this disorder. In Chile, PFA seasonal records have registered up to 78% incidence in some growing areas. From the 2004-2005 season up till the present, Aminoethoxyvinylglycine (AVG) had been evaluated for ‘Serr’ PFA control, in order to determine wetting requirements, chemical dosages, and treatment timings. A dose of 125 grams a.i. per hectare resulted in good PFA control. Half of that concentration showed erratic performance, and a double dose did not improve PFA control significatively. One of the most important determinants is the moment of application. Our best results were obtained between 20 to 30% female flower receptivity. Applications at 10% receptivity resulted in less PFA control, probably due to the long bloom period occurring in some areas, and some seasons. This treatment was commercially used in more than 1,000 hectares in Chile, changing ‘Serr’ production in Chile dramatically. Additionally, others chemicals are in evaluation under Chilean conditions, in order to manage this disorder.