New Zealand Journal of Crop and Horticultural Science abstracts
Economics of reducing fungicide use by weather-based disease forecasts for
control of Venturia inaequalis in apples
R. M. BERESFORD
The Horticulture and Food Research Institute
of New Zealand
Private Bag 92 169
Auckland, New Zealand
D. W. L. MANKTELOW
The Horticulture and Food Research Institute
of New Zealand
P.O. Box 85
Hastings, New Zealand
Abstract In seven field trials conducted over four seasons,
black spot incidence was consistently greater in treatments where fungicide use
was reduced by timing sprays with weather information compared to standard
calendar-based treatments. Fungicide use was measured as the total number of
label-rate applications of fungicides with activity against black spot and the
individual components of mixed applications of fungicides were counted
separately. Over all trials, the mean disease incidence at harvest increased
logarithmically as the number of fungicide applications decreased. A regression
equation describing disease increase in terms of number of fungicides and
number of infection periods was used in an economic analysis of apple
production. When the savings from reduced fungicide use were weighed against
the increased harvesting and grading costs and revenue losses from increased
disease, there appeared to be scope to reduce fungicide use by up to 25% before
increased disease adversely affected profitability. Where disease risk was
lower because of fewer infection periods, savings of up to 56% appeared to be
feasible. It was concluded, however, that because fruit harvesting and grading
costs are ahigh proportion of total costs, because they increase with
increasing disease incidence and because cost savings from reducing fungicide
use are a relatively small proportion of total costs, there is at present
little economic incentive for apple growers to reduce fungicide use.
Keywords apples; Venturia inaequalis; black spot; scab;
disease forecasting; reduced fungicide use; economics; cost benefit analysis
PDF file of entire paper: medium quality (558K); (scanned from paper original: notes about this process)
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