Preference of Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) and biochemical analysis of different genetic materials of Eucalyptus

Thaumastocoris peregrinus is an insect pest that causes a reduction in the productivity of Eucalyptus. Control of this insect can be carried out through selection of its less preferred genetic materials. The aim of this research was to evaluate the preferences of T. peregrinus and to associate these with the biochemical composition of six genetic materials of Eucalyptus, collected in an experimental area of the Federal University of Technology - Paraná. Three bioassays were performed: Bioassay 1 conferred the feeding preference of adults of T. peregrinus, through a multiple choice test among the genetic materials; Bioassay 2 evaluated the confinement of the insects, observing the presence of insects, feces, and eggs on the leaves, for a five-day period; Bioassay 3: biochemical analyses were performed on leaves collected from the genetic materials in three different treatments. The preferred genetic material for feeding of T. peregrinus was Clone H-13 and the least preferred was Clone GFMO-27. In the confinement test, the highest percentage of live insects was on Eucalyptus propinqua and the lowest percentage on Eucalyptus pellita × Eucalyptus tereticornis. The biochemical levels of proteins, total and reducing sugars, and phenylalanine ammonia lyase (PAL) activity demonstrated specificity regarding changes after 24 h of exposure to T. peregrinus. In Clone H13, there was a greater increase in the activity of the PAL enzyme, demonstrating that there was a defense response on the part of the plant, however, not sufficient to deter the insects.