SURVEY OF CHEMICAL FRUIT THINNERS FOR ASIAN PEAR CV. HOSUI

In order to establish the effect of Ethephon and NAA as thinners in Asian pears, as well as some of the factors that affect its effectiveness, two trials were carried out in the area of Placilla in the 6th Region of Chile.
Ethephon was applied at 0, 100, 200 and 400 ppm of a.i. at full bloom, NAA was applied at balloon stage, petal fall and 10 days after petal fall (dapf) in concentrations of 5, 10 and 20 ppm.
Applications of NAA included Citowett as wetting agent (0.025%). Approximately 40 days after bloom, the effect of thinning measured as fruits per cm² of trunk cross sectional area (TCSA) was evaluated, and the trees were hand thinned to adjust fruit load.
Results equations were developed.
Ethephon shows an important thinning effect up to 200 ppm.
As result of the more severe thinning a constant increase in average fruit weight (r²=0.53) is shown.
Also, yield efficiency is reduced and fruits tend to adopt a flatter shape (r²=0.59). The effect of NAA was higher in the earlier application dates, with a high response in proportion with the concentration.
The thinning effect is lower 10 dapf.
In both cases, fruit weight depends on fruit load left after final fruit set (r²=0.56 for NAA and r²=0.52 for Ethephon), the same occurred with yield efficiency, although tendencies show a decrease of both variables for Ethephon for a same fruit load.

VII International Symposium on Pear Growing

G. Reginato, A. Rojas

Fruit thinning, NAA, Ethephon, rates, timing

https://doi.org/10.17660/ActaHortic.1998.475.32