Open AccessSpill-over attack by the gall fly, Urophora stylata, on congeners of its target weed, Cirsium vulgare
Author(s) -
Michael G. Cripps,
Jovesa Navukula,
Benjamin Kaltenbach,
Chikako van Koten,
Seona Casonato,
H. Gourlay
Publication year - 2020
Publication title -
proceedings of the new zealand weed and pest control conference/new zealand plant protection/proceedings of the ... national weeds conference/proceedings of the new zealand weed control conference/proceedings of the new zealand plant protection conference
Language(s) - English
Resource type - Journals
eISSN - 0370-2804
pISSN - 0370-0968
DOI - 10.30843/nzpp.2020.73.11718
Subject(s) - thistle , cirsium arvense , biology , weed , gall , biological pest control , noxious weed , tephritidae , agronomy , botany , pest analysis
The gall fly, Urophora stylata, was released in New Zealand in 1998 as a biocontrol agent for the thistle weed, Cirsium vulgare (Scotch thistle). In the summer of 2018, a survey was conducted to assess the field host range of the biocontrol agent in New Zealand. A random selection of 18 pasture populations under sheep and/or beef production, where C. vulgare was present, was surveyed to quantify the attack intensity (gall size relative to seedhead size) on C. vulgare, and the presence of attack on other thistle weeds within the same population. At each location, seedheads were collected from C. vulgare and all other thistle species (Cardueae) present, which included Cirsium arvense (Californian thistle), Cirsium palustre (marsh thistle), Carduus nutans (nodding thistle), and an Arctium species (burdock). In addition to attack on C. vulgare, the gall fly was recorded on C. arvense (at six locations) and C. palustre (at one location). The probability of the presence of attack on C. arvense was positively correlated with the attack intensity on C. vulgare, suggesting that attack on C. arvense is a ‘spill-over effect’ occurring where seedheads of C. vulgare are in limited supply.