Intensidade e tipos de injúrias causado às gramíneas por Mahanarva spp. e Notozulia entreriana (Hemiptera: Cercopidae)

Abstract

Spittlebug are one of the main pests of grasses (Poaceae), feeding on these plants throughout their life cycle. The nymphs are found in the soil surrounded by a white foam that provides them with protection, while they feed on the xylem of the roots. The adults, on the other hand, are found in the leaves, feeding and inserting toxins present in the saliva that impair the photosynthetic process of the plants, causing chlorosis in the leaves, which can lead to the death of the plant. These insects have a wide geographic distribution and can be found on all continents, except in the tropics, being of great economic importance as pests of cultivars such as Urochloa ruziziensis, Urochloa decumbens, Urochloa humidicola and Saccharum officinarum L. For a better understanding of the injury capacity that these insects have, field experiments were carried out, which consisted of separating 4 different areas for the sampling of grasses every 15 days, where the parameters of wet mass (MU) and dry mass (MS) were analyzed, and compared with the control group that was isolated by a wooden cage in each sampling area, covered with voile to prevent spittlebugs from contaminating this group. In addition to these samplings, a study of the population dynamics of these insects was carried out every 15 days. In a controlled experiment in the laboratory, the injury capacity of two genera of spittlebug, Mahanarva and Notozulia, was evaluated. For this, Urochloa ruziziensis seeds were sown in 65 plastic pots of 18 cm³, with fertilization of NPK 8-28-16. After the development of B. ruziziensis, they were pruned to a height of 15 cm and exposed to different levels of leafhopper infestations, 0, 4, 8, 12 and 16 spittlebug per pot, in a total of 5 replications, with three different groups. Group 1 was infested only with Mahanarva spp., group 2 only with Notozulia entreriana and finally group 3 was infested with half of each genus. At the end of the experiments, it was found that, among the spittlebug, the most frequent genus is Mahanarva with 62.41% and Notozula with only 37.59%. The data obtained on the injury capacity of these insects point to a greater damage capacity of the spittlebug of the genus Mahavarva, demonstrating a greater capacity to cause injuries to grasses than Notozulia.