Monitoring neonicotinoid resistance in biotype B of Bemisia tabaci in Florida.
BACKGROUND
Biotype B of the sweetpotato whitefly, Bemisia tabaci (Genn.), is a worldwide pest that has developed resistance to many insecticides, including the neonicotinoid class. Florida field populations were monitored for susceptibility to the neonicotinoids imidacloprid and thiamethoxam using a cut leaf petiole bioassay method.


RESULTS
Average RR(50) values for imidacloprid increased from 3.7 in 2000 to 12.0 in 2003; decreased to 5.0 and 2.5 in 2004 and 2005, respectively; and then increased to 26.3 and 23.9 in 2006 and 2007, respectively. Populations with RR(50) values of about 50 to 60 during generation one reverted to RR(50) values of < or =4 in six generations, when reared without further exposure to imidacloprid. Average RR(50) values for thiamethoxam increased from 2.0 in 2003 to 24.7 in 2006 and decreased to 10.4 in 2007. Populations with RR(50) values of about 22, 32 and 53 during generation one declined to 8, 5 and 6, respectively, after being reared for five generations without exposure to thiamethoxam. The correlation coefficient from the 26 populations that were bioassayed both with imidacloprid and thiamethoxam showed a significant positive correlation (R(2) = 0.58) between these populations.


CONCLUSIONS
The high level of RR(50) values to imidacloprid and thiamethoxam suggest an unstable decline in the susceptibility of B. tabaci to imidacloprid and thiamethoxam, with possible cross-resistance or predisposition for dual resistance selection.
University of Florida, IFAS, Gulf Coast Research and Education Center, Wimauma, FL 33598, USA.
David J
DJ
Schuster
Rajinder S
RS
Mann
Marco
M
Toapanta
Roberto
R
Cordero
Sandra
S
Thompson
Sabrina
S
Cyman
Aaron
A
Shurtleff
Roy F
RF
Morris Ii
D000818:Animals; D005431:Florida; D006430:Hemiptera / Q000187:drug effects* / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology*; D010078:Oxazines / Q000494:pharmacology*; D000077922:Thiamethoxam; D013844:Thiazoles / Q000494:pharmacology*
D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D013844:Thiazoles; C082359:imidacloprid; D000077922:Thiamethoxam