EFFECTS OF POTASSIUM SILICATE APPLICATION ON PAPAYA PLANTS IN THE TWOSPOTTED SPIDER MITE POPULATION

Abstract

The study objective was to determine whether potassium silicate application on papaya plants induces resistance to twospotted spider mite, Tetranychus urticae, and decreases its infestation. In greenhouse, the effects of potassium silicate in foliar and soil application on seedlings artificially infested, were evaluated. Two doses of potassium silicate 2 and 4L. ha(-1) applied at different times were tested, resulting in treatments with different spray frequencies. Mites were submitted to three assessments, 20, 30 and 40 days after infestation, counting the number of eggs, mites and exuviae of T. urticae present along the main vein. In laboratory, fertility life tables of T. urticae fed with papaya leaves taken from plants of treatments receiving foliar application of potassium silicate were built. The residual effect was evaluated by spraying leaf discs in a Potter tower and transfer of females after 24 hours. Physiological analyses of leaves were performed to assess the physiological components indicative of activation of the defense mechanism of plants. The application of potassium silicate induced the production of plant defense substances reducing the net reproduction rate values (Ro). On the other hand, in the experiment about residual effect, it was observed hormoligosis induction with increased number of eggs per female. In the greenhouse, potassium silicate application did not result in reduced T. urticae infestation.