New Zealand Journal of Crop and Horticultural Science abstracts
Disease severity keys for powdery and downy mildews of pea,
and powdery scab of potato
R. E. FALLOON
S. L. H. VILJANEN-ROLLINSON
G. D. COLES
J. D. POFF
New Zealand Institute for Crop & Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
Abstract Disease severity keys are described and illustrated
for powdery mildew (Erysiphe pisi DC.) and downy mildew (Peronospora
viciae (Berk.) Caspary) of pea (Pisum sativum L.), and powdery scab
(Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea
Tomlinson) of potato (Solanum tuberosum L.). The keys consist of
illustrations of pea leaves or potato tubers in 11-point (0-10) severity scales
of arbitrary proportions of surface areas diseased. The keys were constructed
from hand drawings of pea leaflets or potato tubers, with colonies or lesions
drawn to resemble typical infections of the respective diseases. Proportions of
surface area of plant parts "diseased" on drawings were confirmed using
computer-assisted image analysis. The drawings were then scanned into computer
storage for manipulation into illustrated keys for publication. The complete
keys, or abbreviated versions, have been used for assessing severity of the
diseases in recent research on crop loss assessment, disease control,
susceptibility assessment, and disease epidemiology. They also provide bases
for accurate disease severity assessment in commercial pea and potato crops.
Copies of the disease keys are available from the senior author.
Keywords disease severity assessment; illustrated keys;
powdery mildew; Erysiphe pisi DC.; downy mildew; Peronospora
viciae (Berk.) Caspary; pea; Pisum sativum L.; powdery scab;
Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea
Tomlinson; potato; Solanum tuberosum L.
New Zealand Journal of Crop and Horticultural Science, 1995, Vol. 23:
31-37
0114-0671/95/2301-0031 $2.50/0 (c) The Royal Society of New Zealand
1995
PDF file of entire paper: medium quality (510K); (scanned from paper original: notes about this process)
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