New Zealand Journal of Agricultural Research abstracts
Effect of potato mirid (Calocoris norvegicus) on white clover seed
production in small cages
N. C. SCHROEDER
R. B. CHAPMAN
Department of Entomology and Animal Ecology
P. O. Box 84
Lincoln University
Lincoln, New Zealand
P. T. P. CLIFFORD
AgResearch Grasslands
P. O. Box 60
Lincoln, New Zealand
Abstract Potato mirid, Calocoris norvegicus, commonly
occurs in white clover, Trifolium repens, crops in Canterbury, New
Zealand. Its potential to reduce seed yield by feeding injury was investigated
in field cage plots in a cv. Huia white clover seed crop. Third to fifth instar
nymphs were released at five intensities ranging from 0 to 2 mirids per 5
stolons. Plant growth and inflorescence production were determined by regular
measurements of 15-20 tagged stolons per cage. Seed was harvested in late
summer and dressed into first and second quality seed for which thousand seed
weights were recorded. No differences between plant growth and flowering
pattern were observed between treatments, but inflorescence numbers were
quadratically reduced as mirid numbers increased. When total plot flowering and
yield components were compared, a significant negative quadratic relationship
between total inflorescences and first quality seed yield with increasing mirid
intensity was demonstrated. For second quality seed yield a negative linear
relationship was observed. A positive linear relationship between undamaged
inflorescences and total yield per plot was also demonstrated. On the basis of
current returns for white clover seed ($4 kg-1), losses of up to
$740 ha-1 were estimated.
Keywords Potato mirid; Calocoris norvegicus;
white clover; Trifolium repens; seed yield; feeding injury
New Zealand Journal of Agricultural Research, 1998, Vol. 41: 111-116
0028-8233/98/4101-0111 $7.00/0 (c) The Royal Society of New Zealand
1998
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