The invasive seed bugLeptoglossusoccidentalis, a species native to Western North America, is of major concern for the producers of stone pine seeds in the Mediterranean countries. The large size of these edible seeds and their nutritive content may represent a pull factor for the seed bug. Cone and seed traits of three main Mediterranean pine species:P.pinea,P.pinaster, andP.halepensis, were evaluated. Preference trials with cone-bearing branches, individual cones and seeds were conducted to test host preference among the three host species.Considering the kernel size, stone pine seeds provide 4 to 13 times more reward thanP.pinasterandP.halepensisseeds, respectively, but also needed a greater effort to be reached as measured by coat thickness. Still, the benefit/cost ratio was higher onP.pinea. Individual seeds and cones ofP.pineawere 2 to 3 times more consumed than those of the two other pine species. However, branch preference trials did not reveal any difference in bug visits. Moreover, adults manifested strong group behaviour on branches, frequently dissociating into two persisting groups. The implications of these results forP.pineaproducing areas are discussed.
Freezing injury in primary and secondary needles of Mediterranean pine species of contrasting ecological niches
