SUSCEPTIBILITY OF DIFFERENT EUCALYPTUSSPECIES TO NATURAL INFESTATION OF THE RED GUM LERP PSYLLID IN SARDINIA (ITALY)

摘要

Glycaspis brimblecombei Moore (Hemiptera: Psyllidae), the red gum lerp psyllid, is a Eucalyptus exotic pest accidentally introduced in Europe during 2009 and reported in Italy in 2010. Since its first arrival in Sardinia (insular Italy) in 2011, the pest has widely spread throughout the island on Eucalyptus camaldu-lensis Dehnh., the most common species in the area, seriously affecting the production of honey from this species. Within a regional study program on the management of the pest, two experiments were carried out to evaluate the susceptibility of four Eucalyptus species (E. camaldulensis, E. globulus Labill., E. gom-phocephala DC and E. occidentalis Endl.) to G. brimblecombei under field conditions, and assess the combined effects on psyllid infestation of two irrigation levels and addition or absence of nitrogen fertilization applied to pot plants. Seedlings of the abovementioned species exposed to natural infestation during the peak of psyllid population showed significantly different levels of pest density related to host plant species, resulting in E. camaldulensis and E. globulus respectively, the most and the less susceptible to G. brimblecombei. Eggs were laid and hatched on E. gomphocephala and E. occidentalis as well, but withinthe duration of the experiments, complete development of juveniles was observed only on E. camaldulensis. With regard to the effect of treatments, the combination of high irrigation rates and nitrogen fertilization led to higher psyllid infestation of seedlings, in respect of low irrigated unfertilized pots, and this treatment resulted in significant differences among eucalyptus species in terms of G. brimblecombei density. Furthermore, pest density increased with the increase of foliar nitrogen contentand the number of young leaves, both higher in plants under high irrigation and fertilization treatments. These findings may have interesting implications for the cultivation of new Eucalyptus plantations in areas under heavy red gum lerp psyllid infestation.