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New Zealand Plant Protection 66 (2013): 383

Screening supplements to enhance the biological control activity of HR42 against Colletotrichum acutatum

M.J. Vergara, N.J. Larsen, I.P.S. Pushparajah and K.R. Everett


Ten compounds were evaluated for their effects on the efficacy of the bacterial biological control agent (BCA) HR42 against the avocado postharvest rot fungus, Colletotrichum acutatum. The effects of the 10 compounds (chitin, D-glucose, glycol chitosan, L-serine, L-aspartic acid, calcium chloride, calcium carbonate, potassium chloride, ammonium molybdate and sodium carbonate) at four different concentrations (1, 10, 100 and 1000 mM) were tested separately on bacterial and fungal growth. L-serine, L-aspartic acid and calcium chloride all stimulated growth of HR42 and suppressed mycelial growth of C. acutatum. The BCA and these compounds were then tested in combination on detached avocado fruit for their ability to inhibit lesion development following wound-inoculation. A high concentration of HR42 (107 cfu/ml) significantly inhibited the development of lesions caused by 105 and 107 conidia/ml of C. acutatum. There was no improvement of control by the addition of any of the three compounds. These results show that HR42 has biocontrol activity against C. acutatum in a detached fruit test, but there was no enhancement of control by the addition of supplements.

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