DEFENSIVE ROLE OF ALLIUM SULFUR-COMPOUNDS FOR LEEK MOTH ACROLEPIOPSIS-ASSECTELLA Z (LEPIDOPTERA) AGAINST GENERALIST PREDATORS

It has been shown previously that sulfur volatiles produced by Allium plants affect the behavior of their specialist phytophages and of their specialist entomophages. The action of these compounds in protecting the leek moth Acrolepiopsis assectella against generalist entomophages was studied in comparison to the proposed original defensive role of these compounds against generalist herbivorous insects. Two ants species, Formica selysi and F. fusca, were used as generalist predators. Six behavioral criteria of the predatory behavior of the ants were studied in presence of the last-instar caterpillars (C5). C5 reared on artificial diets with or without leek components were tested, as well as C5 soaked in frass of leek-reared caterpillars or disulfide solutions. In addition, the response of the ants to pure chemicals found in leek was studied using honey solutions with or without sulfur compounds. The sulfur allelochemicals of Allium plants have a negative action on predatory ants. Interestingly, the nonvolatile precursors of sulfur volatiles of Allium plants seem to have a protective role for their phytophagous insects against generalist entomophages.