FIELD SPRAYS OF BACILLUS-SUBTILIS AND FUNGICIDES FOR CONTROL OF PREHARVEST FRUIT DISEASES OF AVOCADO IN SOUTH-AFRICA

In 3 consecutive years, preharvest applications of Bacillus subtilis f ield sprays integrated with copper oxychloride or benomyl consistently reduced severity of avocado black spot (BS), caused by Pseudocercospo ra purpurea at Omega, Republic of South Africa. Control was equal to t hat obtained with copper oxychloride or benomyl-copper oxychloride in the first and third years of spraying at Omega. In the second year, on ly the integrated treatment controlled BS, while copper oxychloride pr oved ineffective. The antagonist was applied on its own or integrated with copper oxychloride sprays at two other geographically distinct lo cations, Westfalia Estate and Waterval. The integrated and biological treatments at these localities were less effective than copper oxychlo ride sprays in controlling BS disease. Integrated control was more eff ective than B. subtilis sprays at Westfalia. On continuation of the bi ological spray program at Waterval for an additional three seasons, co ntrol was as effective as copper oxychloride in the last 2 years of sp raying. Sooty blotch (SE), caused by an Akaropeltopsis sp., was reduce d by the integrated treatment at Omega during the second season and at Westfalia during the first season. Although the two fungicide treatme nts reduced SE at Omega in the first season, copper oxychloride increa sed it above that of the control in the third season. Only the copper oxychloride treatment reduced SE at Waterval in the third season, whil e the B. subtilis treatment increased disease above that of the contro l in the fourth season.