Abstract
The tobacco whitefly, Bemisia tabaci, is one of the major insects infesting vegetable plants. This pest is well known in Alhassa oasis, Saudi Arabia; which is historically agricultural land cultivated with date palm trees and different vegetables. A molecular key based on the sequence of the mitochondrial cytochrome oxidase gene CO1 was used for the identification of strains of the tobacco whitefly Bemisia tabaci collected from farms located in four areas of the Alhassa oasis; Northern, Southern, Eastern and Western. Only one biotype (B-biotype) of B. tabaci was reported in the oasis. Resistance of B. tabaci was tested against eight insecticides, the results showed moderate to low levels of resistance to the tested insecticides. However, the resistance to neonicotinoid insecticides was low and established at 1.3 fold to both Imidacloprid and Acetamiprid. In addition, medium levels of resistance were detected to the insect growth regulator Pyriproxyfen (30 fold), and the pyrethroid Deltamethrin (30 fold), Bifenthrin (24 fold) and Cypermethrin (13 fold). A medium level of resistance was also detected to the carbamate insecticide Carbosulfan and was 40 fold of the laboratory strains. A low level of resistance to the organophosphorus insecticide was detected to Phenthoate (11 fold). However, these results reflect that the farmers were less dependent on the use of insecticides to control B. tabaci in the oasis and they may be implementing other environmentally sound techniques to keep the pest below the damage threshold.