Field Sprays of Bacillus subtilis and Fungicides for Control of Preharvest Fruit Diseases of Avocado in South Africa

Abstract

In 3 consecutive years, preharvest applications of Bacillus subtilis field sprays integrated with copper oxychloride or benomyl consistently reduced severity of avocado black spot (BS), caused by Pseudocercospora purpurea at Omega, Republic of South Africa. Control was equal to that obtained with copper oxychloride or benomyl-copper oxychloride in the first and third years of spraying at Omega. In the second year, only the integrated treatment controlled BS, while copper oxychloride proved ineffective. The antagonist was applied on its own or integrated with copper oxychloride sprays at two other geographically distinct locations, Westfalia Estate and Waterval. The integrated and biological treatments at these localities were less effective than copper oxychloride sprays in controlling BS disease. Integrated control was more effective than B. subtilis sprays at Westfalia. On continuation of the biological spray program at Waterval for an additional three seasons, control was as effective as copper oxychloride in the last 2 years of spraying. Sooty blotch (SB), caused by an Akaropeltopsis sp., was reduced by the integrated treatment at Omega during the second season and at Westfalia during the first season. Although the two fungicide treatments reduced SB at Omega in the first season, copper oxychloride increased it above that of the control in the third season. Only the copper oxychloride treatment reduced SB at Waterval in the third season, while the B. subtilis treatment increased disease above that of the control in the fourth season.

Controle alternativo de Colletotrichum acutatum agente causal da queda prematura dos frutos cítricos

“…Em outras culturas, Baker et al (1983) verifi caram que a severidade da ferrugem do feijoeiro foi reduzida em, pelo menos, 75%, em 1982 e 1983, com três aplicações por semana de B. subtilis, apresentando o mesmo nível de controle, quando comparado ao fungicida mancozeb, aplicado uma vez por semana. Korsten et al (1997) Embora a quantidade de doença não tenha sido sufi cientemente alta para mostrar com maior nitidez a efi ciência dos tratamentos, os agentes de controle biológico e os biofertilizantes utilizados, isoladamente ou em combinação com os antagonistas, apresentaram potencial para o controle da QPFC, com exceção dos tratamentos Bio 2+ACB-37 e a mistura dos isolados de B. subtilis, os quais não diferiram da testemunha.…”

A Box-Behnken design for predicting the combined effects of relative humidity and temperature on antagonistic yeast population density at the surface of apples

“…Biocontrol of postharvest fruit decays is achievable by postharvest application of antagonists and by preharvest spraying of biocontrol agents in the field (Benbow and Sugar 1999;Korsten et al, 1997;Leibinger et al, 1997;Teixidõ et al, 1998a). In the latter practice, the antagonist is applied just before harvest so that it can colonize the fruit surface and any wounds inflicted during harvest before the arrival of wound pathogens (Ippolito and Nigro, 2000).…”

Factors determining use of biological disease control measures by the avocado industry in South Africa

“…This is despite the fact that the biocontrol agent has previously been shown to be effective to control avocado fruit diseases (Korsten et al, 1997). Results indicated that respondents generally demonstrated a positive attitude towards biological control and believed in the long term effectiveness of this approach as a disease control method.…”

“…Currently, the pre-harvest disease control program for these pathogens involves sprays with copper-based fungicides (Towsen et al, 1995). According to Korsten et al (1997), copper oxychloride proved to be ineffective against Cercospora spot of avocado during one field trail (Korsten et al, 1997). This might be attributed to the wash-off effect of copper during times of rain that result in poor fruit coverage and therefore achieving lower levels of control (Everett et al, 2005).…”