Current status of insecticide resistance in Q biotype Bemisia tabaci populations from Crete.
BACKGROUND
A major problem of crop protection in Crete, Greece, is the control of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) with chemical insecticides owing to the rapid development of resistance. The aim of this study was to investigate the establishment of resistance and the underlying mechanisms to major insecticide classes with classical bioassays and known biochemical resistance markers.


RESULTS
During a 2005-2007 survey, 53 Q biotype populations were collected. Application history records showed extensive use of neonicotinoids, organophosphates, carbamates and pyrethroids. High resistance levels were identified in the majority of populations (>80%) for imidacloprid (RF: 38-1958x) and alpha-cypermethrin (RF: 30-600x). Low resistance levels (RF < 12) were observed for pirimiphos-methyl. A strong correlation between resistance to imidacloprid and the number of applications with neonicotinoids was observed. Significant correlations were observed between COE and P450-dependent monoxygenase activity with resistance to alpha-cypermethrin and imidacloprid respectively. A propoxur-based AChE diagnostic test indicated that iAChE was widespread in most populations. Resistance levels for alpha-cypermethrin were increased when compared with a previous survey (2002-2003). Differentiation of LC(50) values between localities was observed for imidacloprid only.


CONCLUSIONS
Bemisia tabaci resistance evolved differently in each of the three insecticides studied. Imidacloprid resistance seems less established and less persistent than alpha-cypermethrin resistance. The low resistance levels for pirimiphos-methyl suggest absence of cross-resistance with other organophosphates or carbamates used.
Roditakis
Emmanouil
E
National Agricultural Research Foundation, Plant Protection Institute of Heraklion, PO Box 2228, 71003 Heraklion, Greece. e-roditakis@her.forthnet.gr
Grispou
Maria
M
Morou
Evangelia
E
Kristoffersen
Jon Bent
JB
Roditakis
Nikos
N
Nauen
Ralf
R
Vontas
John
J
Tsagkarakou
Anastasia
A
D000818:Animals; D006115:Greece; D006430:Hemiptera / Q000145:classification / Q000187:drug effects* / Q000201:enzymology; D007093:Imidazoles / Q000494:pharmacology; D019476:Insect Proteins / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology; D010105:Oxygenases / Q000378:metabolism; D011722:Pyrethrins / Q000494:pharmacology
D007093:Imidazoles; D019476:Insect Proteins; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D011722:Pyrethrins; C017160:cypermethrin; C082359:imidacloprid; D010105:Oxygenases