Susceptibility to insecticides in the Q biotype of Bemisia tabaci is correlated with bacterial symbiont densities.
BACKGROUND
The presence of symbiotic microorganisms may influence an insect's ability to tolerate natural and artificial stress agents such as insecticides. The authors have previously shown that Rickettsia in the B biotype of the whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) increases this insect's susceptibility to several insecticidal compounds. This communication reports a comparison of the susceptibilities of three isofemale strains of the Q biotype of B. tabaci harbouring different bacterial complements to major insecticides from different chemical groups: one strain harboured only Arsenophonus, one harboured Rickettsia and Arsenophonus and one harboured Arsenophonus and Wolbachia.


RESULTS
The presence of different symbiont combinations in the three strains had a significant influence on their susceptibility to most of the insecticides tested. Thiamethoxam, imidacloprid, pyriproxyfen and spiromesifen had a significant influence on strains that had the double infections Rickettsia-Arsenophonus and Wolbachia-Arsenophonus, which also carried higher amounts of symbionts as assessed by quantitative real-time PCR. No significant differences in mortality rates were observed when the tested strains were treated with diafenthiuron.


CONCLUSIONS
The results suggest a correlation between the presence of high bacterial densities in B. tabaci and the insect's ability to detoxify toxic compounds such as insecticides.
Ghanim
Murad
M
Department of Entomology, Institute of Plant Protection, the Volcani Centre, Bet Dagan 50250, Israel. ghanim@agri.gov.il
Kontsedalov
Svetlana
S
D000818:Animals; D005260:Female; D006090:Gram-Negative Bacteria / Q000235:genetics / Q000502:physiology*; D006430:Hemiptera / Q000187:drug effects* / Q000382:microbiology* / Q000502:physiology; D007306:Insecticides / Q000494:pharmacology*; D013559:Symbiosis
D007306:Insecticides