Controle de Mahanarva frimbriolata (Stål, 1854) (Hemiptera: Cercopidae) em duas variedades de cana-de-açúcar, no estado de Alagoas

Abstract

Despite the easiness of adaptation to the climate of Brazil, pests the culture of the sugarcane faces a series of fitossanitary problem, such as the incidence, that diminish the production and the productivity, causing economic damage for the producers. The spittlebug Mahanarva fimbriolata (Stål, 1854) (Hemiptera: Cercopidae) is one of the main pests of the sugarcane not only in Alagoas as also in other states of Brazil. Currently, in result of the indiscriminate use of insecticides, the use of the Biological Control becomes necessary, which is not pollutant, it does not unbalance the environment and he is not toxic. In this way some plants of the State of Alagoas are using fungous entomopathogenic Metarhizium anisopliae (Metsch.) Sorokin, to reach the control of the spittlebug. This work had as objective to evaluate the efficiency of the Evidence® insecticide and two dosages of biological insecticide M. anisopliae in the control of the spittlebug. Two experiments had been conducted, in the cane-plantation region of the Plant Waterfall located in Maceió-AL, the period understood between July and September of 2006. Initially a population evaluation of nymphs and adults was carried through and the others to the 15, 30 and 45 days after the treatments. The application of the insecticides occurred in 19 of July and a reapplication of the biological insecticide in 22 of August. In experiment 1 the nymphs had been observed populations varying of 49 the 67 and the presence of adults of M. fimbriolata were not evidenced. The treatments had not differed between itself to the 5% for the test distribution free of Kruskal-Wallis, but the test of percentage of efficiency of Henderson and Tilton indicated for decreasing order of efficiency percentage the dosages, of 1,5L/ha of Evidence®, 20kg/ha of fungous and 10kg/ha of fungous with 72,48%, 62.35% and 24.76% respectively for nymphs; and 42.25%, 34.54% and 15.51% respectively for adults. In each area the test distribution free of Kruskal-Wallis was observed in accordance with that the numbers of nymphs had differed between the periods in all the treatments and that in the area dealt with Evidence® difference in the number of adults did not only occur 5% of significance. It had a high positive correlation between rainfall and amount of nymphs in the areas dealt with 20kg/ha to fungous and 1,5L/ha of Evidence®. In the area dealt with 10kg/ha to fungous and in the Control, an average correlation was observed. Also it was observed an average negative correlation between rainfall and amount of adults in the treated areas and Control. In experiment 2 the nymphs had been initially observed populations varying of 51 the 101. The presence of adults varying of 1 the 2 was evidenced, the treatments had not differed between itself to the level of 5% of significance for the test of Kruskal-Wallis, but the method of Henderson and Tilton indicated for decreasing order of efficiency percentage the dosages, of 1,5L/ha of Evidence®, 20kg/ha of fungous and 10kg/ha of fungous with 94,33%, 65.08% and 51.37% respectively for nymphs; e 93.33%, 70% and 50% respectively for adults. In each area it was observed for the test of Kruskal-Wallis that the number of nymphs between the periods did not only differ in the Control and that difference in the number of adults in treatment of 10 kg/ha of fungous the 5% of significance only occurred. In all the analyses were applied the Polynomial Regression so that if it could follow the development of the pest. To if analyzing the data they had been evidenced that it occurred a high positive correlation between rainfall and amount of nymphs in the areas dealt with 10 and 20 kg/ha to fungous and with 1,5L/ha of Evidence®, in the Control observed an average correlation. Also an average negative correlation between rainfall was observed and amount of adults of the areas dealt with 10 and 20kg/ha to fungous and Control, however, in the area dealt with 1,5L/ha of Evidence® got a negative correlation decrease. The total cost of the application of the Evidence® had been minor who of the other treatments, but is important to take in consideration the happened risks of the use of the pesticides.