Effects of topical application of hexaflumuron on adult sugar beet weevil Aubeonymus mariaefranciscae, on embryonic development: Pharmacokinetics in adults and embryos

Resum

The pattern of penetration, distribution, and excretion of labeled hexaflumuron on young and old adults of a new sugar beet pest, Aubeonymus mariaefranciscae Roudier (Coleoptera: Curculionidae), and its transovarial effects were investigated. Small differences between young and old adults in penetration and excretion were observed, though at the end the amount of hexaflumuron inside the body reached similar levels. Penetration of [14C] hexaflumuron in females was a little higher than in males, particularly during the first 3 days after application, but excretion was strongly lower in males, resulting in higher retention of insecticide in their bodies than in females. Retention of hexaflumuron in the body was high compared to other insect species. Young adult weevils retain higher amounts of hexaflumuron in the reproductive system than the older ones. Moreover, the low percentage of radiolabeled hexaflumuron recovered in the eggs impaired the embryo development, leading to inhibition of egg hatch. Treatment with hexaflumuron on A. mariaefranciscae adults resulted in obvious symptoms of disorganization in the integument ultrastructure of embryos. The procuticle was particularly affected as a result of low residual amounts of hexaflumuron. Both endo- and exocuticle were totally unstructured and the typical lamellated organization was absent, resulting in an amorphous structure appearance. This effect seems to be related to irregular deposition of chitin-protein layers, leading to mechanical weakness and death of the embryo later on.