Agriculture, Pêche et Aquaculture
Department of Agriculture, Aquaculture and Fisheries
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  Compost Tea Evaluation Initiative: Greenhouse Potato Late Blight Disease Assessment

Khalil Al-Mughrabi1 and Peter Scott1

Partner: Jolly Farmer Products Inc.

Abstract: A greenhouse experiment was conducted at Jolly Farmer Products Inc. in Northampton, New Brunswick between 25 November 2003 and 25 February 2004 to evaluate the efficacy of compost tea + food (TF), food (FD) and Manzate (MZ), against Phytophthora infestans, the cause of late blight disease in potatoes. Treatments were applied at various dates, rates and frequencies. Two controls were tested, one inoculated and untreated (CI) and the other uninoculated and untreated (CN). First inoculation was conducted on 11 Feb and the second on 16 Feb 2004. Two additional treatments were added (treatments A and B). Treatment A received compost tea + food two hours after inoculation with late blight. Treatment B received compost tea + food two days after the inoculation with late blight. Both treatments received a second tea + food application on 16 Feb along with the other trial groups. Two potato varieties, Green Mountain and Russet Burbank, were used. Percent disease incidence and severity were assessed three times. Green Mountain acquired higher percentage of disease severity than Russet Burbank. Disease incidence for combined treatments remained the same and disease severity increased over time. MZ treatment was the best in inhibiting late blight compared to other inoculated treatments. Disease incidence was the lowest (0%) in the uninoculated, untreated control (CI) followed by Manzate treated (MZ) plants (16.7%). None of the treatments other than CN and MZ were significantly different than the control in their effect on late blight incidence. In case of disease severity, a similar trend to that of disease incidence was observed. Disease severity was the lowest (0%) in the uninoculated, untreated control (CI) followed by Manzate treated (MZ) plants (1.08%). Treatments MZ and CN were significantly different than all other treatments. Treatments A, TF and FD were not significantly different from each other and had the highest percent disease severity. Treatments CI and B were in between.

1 NB Department of Agriculture, Fisheries and Aquaculture, Potato Development Centre, 39 Barker Lane, Wicklow, NB, E7L 3S4

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