Insecticide resistance status of Bemisia tabaci Q-biotype in south-eastern Spain.
BACKGROUND
Bemisia tabaci Gennadius Q-biotype has readily developed resistance to numerous insecticide classes. Studies in the Mediterranean area are needed to clarify the resistance status and cross-resistance patterns in this invasive whitefly biotype. The levels of resistance in nymphs of seven strains of B. tabaci Q-biotype from south-eastern Spain to representative insecticides were determined.


RESULTS
Six populations had low to moderate levels of resistance to azadirachtin (0.2- to 7-fold), buprofezin (11- to 59-fold), imidacloprid (1- to 15-fold), methomyl (3- to 55-fold), pyridaben (0.9- to 9-fold), pyriproxyfen (0.7- to 15-fold) and spiromesifen (1- to 7-fold), when compared with a contemporary Spanish Q-biotype reference population (LC(50) = 2.7, 8.7, 15.2, 19.9, 0.34, 20.9 and 1.1 mg L(-1) respectively). A single population collected from a greenhouse subject to intensive insecticide use exhibited generally higher resistance levels to the same array of compounds (31-, 1164-, 3-, 52-, 9-, 19- and 3-fold respectively). Pyridaben and spiromesifen were extremely effective against nymphs of all strains, with LC(50) values significantly below recommended application rates.


CONCLUSIONS
In contrast to previous reports, high rates of efficacy exist for numerous insecticide classes against B. tabaci Q-biotype populations in these intensive agricultural regions of south-eastern Spain. This probably reflects the recent and significant reductions in exposure that have resulted from a wider uptake of IPM technologies and strategies. However, the continued presence of resistance genes also suggests that a reversion to levels of high insecticide exposure could result in a rapid selection for resistance.
Departamento de Producción Vegetal, Universidad Politécnica de Cartagena, Paseo Alfonso XIII 48, 30203 Cartagena, Spain.
Esther
E
Fernández
Carolina
C
Grávalos
Pedro Javier
PJ
Haro
Dina
D
Cifuentes
Pablo
P
Bielza
D000818:Animals; D004351:Drug Resistance; D006430:Hemiptera / Q000187:drug effects* / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology*; D013030:Spain
D007306:Insecticides