Effect of gibberellic acid and (2-chloroethane) phosphonic acid on glochid abscission in cactus pear fruit (Opuntia amyclaea Tenore)

Glochids (small spines) of cactus pear negatively affect harvest operations, and the quality and acceptance of this fruit. Different treatments for pre-harvest removal of glochids were evaluated. Gibberellic acid (GA(3), 100 ppm) was sprayed over flower buds in six consecutive applications (every 7 days) during their development. Also, solutions of (2-chloroethane) phosphonic acid or ethephon ('Ethrel'(R)) at 500, 600; 700, 800, and 900 ppm a.i. were sprayed over the buds immediately after fruit set, alone or in combination with GA(3) applications. At harvest, it was concluded that GA(3) + ethephon treatments generally increased the length as well as the number of glochids compared with glochids on control fruit. Ethephon applications only caused slight abscission of glochids prior to harvest. However, after the mechanical effect of harvest, GA(3) + ethephon treatments caused significant abscission of glochids ( > 90% in the best case) compared with the controls (37%), while ethephon (alone) treatments caused 79% of glochids to abscise in the best case (700 ppm). None of the treatments negatively affected the quality of the fruit in terms of soluble solids concentration, acidity, color, weight of pulp and weight of peel. (C) 2001 Elsevier Science B.V. All rights reserved.