EFFECT OF TIMING OF CAUSTIC BLOOM THINNING SPRAYS DURING BLOOM ON FRUIT SET, YIELD AND FRUIT SIZE OF PEACH

A field study was conducted at Geneva, New York, USA in 2008 where we evaluated the effect of timing of spray application the 2 caustic bloom thinning chemicals, ammonium thiosulfate (ATS) and lime sulfur + fish oil (LS+FO) on ‘Redhaven’ and ‘Babygold 5’ peach trees on Bailey rootstock.
The trials were sprayed with an airblast sprayer at 1,200 liter/ha water volume.
ATS was sprayed at a concentration of 4 liter / 100 liter water while LS+FO was sprayed at a concentration of 4 liter / 100 liter water of LS and 2 liter / 100 liter water of FO. Trees were treated either on the day of the first open blossom or at one day intervals thereafter for the next 7 days.
ATS caused more thinning than LS+FO at each timing except on day 7 when trees were at petal fall.
Both blossom-thinning chemicals were less effective on the first day blossoms were open than 2-3 days later.
At 4-5 days after the first open blossom both chemicals were less effective while at 6 days after the first open blossom ATS was again effective and at 7 days after first open blossom LS+FO was an effective thinner.
Fruit size was greatest and yield was lowest at 2 days after first open blossom.
With ‘Redhaven’ this timing resulted in over thinning. The best timing appeared to be when 30-40% of the blossoms were open and when 80% of the blossoms were open.

VIII International Peach Symposium

T.L. Robinson, L.I. Dominguez

Prunus persica, ammonium thiosulfate, lime sulfur, fish oil

https://doi.org/10.17660/ActaHortic.2015.1084.65