New Zealand Journal of Crop and Horticultural Science abstracts
Short communication: Potential ascospore production and resulting blossom blight by Monilinia
fructicola in unsprayed peach trees
K. G. TATE
Crop Health Services
P. O. Box 2153
Stortford Lodge, Hastings
New Zealand
gtate@inhb.co.nz
P. N. WOOD
The Horticultural and Food Research
Institute of New Zealand Ltd
Private Bag 1401, Havelock North
New Zealand
Abstract Apothecial emergence of
Monilinia fructicola
Wint. (Honey), potential ascospore dose (PAD), infection periods (IPs), and
blossom blight (BB) were quantified in a peach (
Prunus persica) block in
1996 during bloom. Flowering began on 21 August, with full bloom 1-7 September
and last flowers on 20 September. First apothecia appeared on 25 August after
15 mm rain on 18-20 August, but shrivelled after a few days of drying
weather. Main apothecial emergence began, peaked, and declined on 4, 7, and 13
September respectively. Apothecial density from 4 to 13 September was 4.4 per
m
2 of ground but 90% of these were confined to a 15 m wheel rut
in the observation plot. Apothecia on bare ground were short-lived compared
with those protected by overhanging grass. Total hymenial surface area within
the observation plot was 58.7, 88.6, 18.2, and 5.7 cm
2 on 4, 7,
10,
and 13 September respectively. PAD on each date was 9.35, 14.14,
2.85, and 0.92 x 10
6/m
2, or 27.26 x
10
6/m
2 for the whole period. From 4 to 6 September,
airborne ascospores trapped by a cyclone spore trap during daylight ranged from
0 to 39/litre air per min. Percentage of flowers contaminated by spores on 3,
5, 12, and 20 September was 10, 65, 68, and 92% respectively. Moderate IPs
occurred on 2, 3, 5, 11-12 September, marginal on 16 September, and light on 19
September, resulting in blossom infections of 3, 12, 29, 29, 5, and 50%
respectively. This corresponded to natural BB levels of 25% on 7 September and
62% on 27 September. A gradient of increasing BB from the windward to leeward
end of the plot occurred. Primary inoculum for BB up to 15 September was
primarily ascospores, and thereafter conidia. Sources of conidia were initially
twig cankers, then diseased blossoms.
Keywords peach; brown rot; Monilinia fructicola;
blossom; apothecia; ascospores
H99050
Received 3 December 1999; accepted 7 April 2000
PDF file of entire paper: medium quality (443K); (scanned from paper original: notes about this process)
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