Population dynamics of the New Zealand flower thrips (Thrips obscuratus) and possible consequences for the incidence of Botrytis bunch rot in grapes
Schmidt K1, Wratten SD1, Teulon DAJ2, Jaspers MV1, Beever RE3
1National Centre for Advanced Bio-Protection Technologies, PO Box 84, Lincoln University, Canterbury, New Zealand.
2New Zealand Institute for Crop & Food Research Limited, Private Bag 4704, Christchurch, New Zealand
3Landcare Research, Private Bag 912170, Auckland, New Zealand
Correspondence: schmidtk@lincoln.ac.nz
Thrips obscuratus, the New Zealand Flower Thrips (NZFT) is endemic to New Zealand and is the most widespread of the New Zealand thrips. It is a well known pest of stonefruit, where its feeding activities cause distortion and damage to ripe fruit and act as a vector for Monilinia fructicola. This thrips species also occurs in vineyards during flowering, when adults and larvae feed on nectar and pollen, causing considerable loss of viable pollen and also damage the ovaries. T. obscuratus can achieve densities of up to two million per hectare in vineyards. Since it is so abundant, this species may have a major effect on grape and disease development. In the 2004/2005 season, different types of traps were used to monitor T. obscuratus flight activity and its presence at two field sites in the New Zealand South Island regions of Nelson and Canterbury. Initial results showed that large populations of airborne thrips at flowering probably originated from sources outside the vineyards. Their colonization of the vines led to high numbers of eggs and larval stages on bunches. The interaction between NZFT and Botrytis bunch rot was investigated in greenhouse and field trials by introducing a marker strain of B. cinerea, with and without NZFT, to grape flowers enclosed in fine silk bags. When NZFT was present on flowers, the berries developed corky scars and had a greater incidence of B. cinerea infection in some treatments.
