New Zealand Journal of Crop and Horticultural Science
abstracts
Efficacy of integrated postharvest treatments against mixed innoculations
of Penicillium
digitatum and Geotrichum citri-aurantii in ‘Leng’ navel
oranges (Citrus sinensis)
N. M. Cunningham
P. D. Taverner
South Australian Research and Development
Institute
Box 397, GPO Adelaide
SA 5000, Australia
email: cunningham.nancy@saugov.sa.gov.au
Abstract Green mould (Penicillium digitatum) and
sour rot (Geotrichum citri-aurantii) in early season, thin-skinned navel
oranges (Citrus sinensis) are of serious concern to the Australian citrus
export industry. The pathogen causing the disease sour rot is particularly
problematic because the control method for the Australian domestic market is
to use fungicides containing guazatine, a chemical that is restricted for important
export markets. In this study, we have examined possible alternative treatments
to combinations of the two pathogens including the use of non-restricted fungicides
in combination with gibberellic acid (GA3), generally regarded as safe (GRAS)
compounds, and/or elevated temperature. When inoculated fruit were dipped in
solutions containing the fungicide imazalil alone and in combination with GA3,
thiabendazole, or carbendazim, the infection rate was reduced. GRAS compounds,
sodium carbonate, and mineral oil, were also effective in reducing infection
rates when mixed with imazalil, as was sodium carbonate alone and when mixed
with GA3. GA3 was not effective at the rate tested (50 mg litre–1). Elevated
temperature in most instances did not reduce disease incidence in fruit, although
in experiments with control levels of inoculation below 80%, temperature was
a factor in some treatments. Further experiments are necessary to demonstrate
the potential of alternative treatments to limit sour rot and mould development
on export fruit.
Keywords gibberellic acid; GRAS compounds; soda ash; Citrus
Postharvest Dip; fungicides; green mould; Penicillium digitatum; sour
rot; Geotrichum citri-aurantii; elevated temperatures; imazalil; thiabendazole;
carbendazim
New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35:
187–192
0014–0671/07/3502–0187 © The Royal
Society of New Zealand 2007
H05131; Online publication date 11 May 2007. Received 31 October 2005;
accepted 31 May 2006
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