Effect of N-1-Naphthyl Phthalamic Acid on Fruit Set of Peaches

Thinning Short-Cycle Florida Peaches with N-1-Naphthylphthalamic Acid1

“…The thinning response to application of 100 ppm 5 days after full bloom was comparable to 300 ppm applied at full bloom. This indicates that thinning can be accomplished at 3 Sodium salt of N-1-naphthylphthalamic acid, 17.2%. NPA effectively thinned short-cycle, low-chilling peaches.…”

“…This fruiting situation is unique because long-cycle northern peaches generally blcom uniformly over a 3-or 4-day period and have a more uniform development with more fruit in the proper stage for chemical thinning. Long-cycle peaches have been successfully thinned with NPA (1,3,6). Cultivars adapted for cooler temperate zones, particularly the long-cycle peaches, also have greater potential for size.…”

“…Four single-tree replications were used at Quincy and 7 at Gainesville. Treatments were 0, 200, and 400 ppm NPA 3 applied to runoff at full bloom and 4 days after full bloom at Quincy and 0, 100, 200, and 300 ppm NPA at full bloom and 5 days after full bloom at Gainesville. Average spacing of fruit on 20 limbs per tree (cm/fruit) was used to determine thinning response on 'Armgold' and 'Q310-7' (2,7,8).…”