New Zealand Journal of Crop and Horticultural Science abstracts
Insecticide bioassays for western flower thrips (Frankliniella occidentalis)
(Thysanoptera: Thripidae) and greenhouse whitefly (Trialeurodes vaporariorum)
(Hemiptera: Aleyrodidae)
N. A. Martin
P. J. Workman
New Zealand Institute for Crop and Food
Research Limited
Private Bag 92 169
Auckland, New Zealand
R. C. Butler
New Zealand Institute for Crop and Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
Abstract Bioassays were tested for their suitability
to determine the resistance of western flower thrips (Frankliniella occidentalis)
and greenhouse whitefly (Trialeurodes vaporariorum) to insecticides.
Adult female greenhouse and lupin strains of western flower thrips were exposed
to bean leaf discs treated with insecticide solutions for 24 h at 25°C.
The susceptibility of greenhouse strain western flower thrips was further
assessed following exposure for 48 h at 25°C to treated bean leaf discs
and plastic Petri dishes, the inside surfaces of which had been sprayed with
insecticide. The susceptibility of adult greenhouse whitefly was compared
when exposed to leaf discs sprayed with insecticide, leaf discs dipped in
insecticide solutions, and insecticide-sprayed Petri dishes. Whitefly mortality
on leaf discs was assessed after 48 h at 25°C and in plastic dishes after
24 h at 15°C in the dark. A further series of bioassays compared the effect
of insecticide on whitefly nymphs after 7 days at 25°C when exposed to
various orientations of buprofezin-sprayed leaf discs, and whole leaves dipped
into buprofezin solutions. The lupin strain of western flower thrips was
more susceptible than the greenhouse strain to fipronol, maldison, methiocarb,
and methamidophos with resistance factors of 14, 19, 26, and 45, respectively.
The greenhouse strain of western flower thrips was more susceptible to dichlorvos,
lambda-cyfluthrin, maldison, and methamidophos in the Petri dish bioassay
than in the leaf disc bioassay, but the thrips were less susceptible to maldison
in 1996 bioassays than in 1993 and 1999. Adult greenhouse whitefly were similarly
susceptible to endosulfan in the three bioassays, but were more susceptible
to methomyl in the Petri dish tests than in the two leaf disc bioassays. Dipped
leaf discs gave lower LC50s of whitefly nymphs than other bioassays,
but there was high variation between runs. The Petri dish bioassay was successfully
adapted for adult western flower thrips and greenhouse whitefly, but its use
is limited by the mode of action of different insecticides, and it is not
suitable for insecticides that only affect juvenile whitefly.
Keywords diagnostic dose; concentration-mortality response
H04094; Online publication date 13 May 2005 Received 5 November 2004; accepted
21 March 2005
New Zealand Journal of Crop and Horticultural Science, 2005, Vol. 33:
177-184
0014-0671/05/3302-0177 © The Royal Society of New Zealand 2005
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