Tests on the effectiveness of kaolin and copper hydroxide in the control of Bactrocera oleae (Gmelin)

Abstract

Repellent and antiovipositional products in the control of Bactrocera oleae (Gmelin) finds a great interest in organic farming, because of the lack of effective products able to kill the olive fly preimmaginal stages. In 2003 in Castelvetrano (Trapani province, Sicily), tests on the effectiveness of Surround WP, a product containing 95% of kaolin, were carried out on three table olive cultivars, Nocellara del Belice, Moresca and Tonda Iblea. In 2004, in the same field and on the same cultivars, BPLK kaolin was tested too. In the second year the two products containing kaolin were also tested on Cerasuola cultivar in an organic olive grove located in Trapani, comparing them with copper hydroxide. At Castelvetrano both in 2003 and in 2004 B. oleae infestation levels of the plots treated with the two products containing kaolin were statistically lower than those of the control plots. In this site, in 2004 Surround WP protected olives significantly better than BPLK kaolin, limiting olive fly harmful infestation up to 17-23% vs. 68-87% of BPLK plots. At Trapani in 2004, the two products containing kaolin and copper hydroxide showed statistically significant differences from the untreated control, but not among themselves, limiting the harmful infestation up to 3-37% vs. 87% of the control. The different results of 2004 recorded by Surround WP and BPLK kaolin in the two olive groves seems linked to the different rainfall of the period after the last treatment, 64 mm in three rainy days at Castelvetrano and 41 mm in eight rainy days at Trapani; BPLK kaolin was probably washed away more than Surround WP. The tested products containing kaolin and copper hydroxide are effectively able to limit B. oleae infestation to a very good level for olive oil production, moreover, considering the earlier harvesting of table olives, these products give a new opportunity for controlling the olive fly also in the organic olive groves for table olives production.