Effect of silicon application to Eucalyptus camaldulensis on the population of Glycaspis brimblecombei (Hemiptera: Aphalaridae).

The use of silicon in forestry has increased recently as it is directly related to improved resistance to insect pests. The red gum lerp psyllid, Glycaspis brimblecombei , occurs in all eucalypt producing regions in Brazil. Two field experiments were conducted to study the effect of silicon applied to Eucalyptus camaldulensis on the psyllid population. In the first experiment, the applications were made via soil (calcium silicate) and leaves (potassium silicate) in a nine months old E . camaldulensis plantation. In the second experiment, we evaluated silicon on seedlings, incorporating it into the substrate (soil) or applying it on leaves (foliar). Monthly, for 24 months, the number of psyllid eggs and immatures were counted on leaf samples. The plant height was measured at 9, 12, 16 and 24 months (experiment 1) and at 4, 8, 12 and 24 months (experiment 2) after application. The numbers of eggs and immatures were lower in periods of higher precipitation, indicating less psyllid attack during the rainy season. The psyllid population was lower in treatments with application of silicon both foliar and via soil compared to control. No significant differences were found in the height of E . camaldulensis plants.