Biologia e exigências térmicas de Diaspis echinocacti (Bouché, 1833) (Hemiptera: Diaspididae) e seu controle com extrato de sisal

Abstract

The forage palm is an important crop that supports the maintenance of agricultural activities in the Brazilian semiarid region. With a xerophilous character, the genera Opuntia and Nopalea have been the main food source for herds, especially in periods of extreme drought. However, the reduction in crop productivity has become a problem, due to the increase in attacks and damage caused by insect pests, such as the scale mealybug Diaspis echinocacti (Bouché, 1833) (Hemiptera: Diaspididae). The objective of this research was to study the biology and thermal requirements of D. echinocacti and its control with sisal extract. The bioassays were carried out in the Entomology laboratory and in a greenhouse at Embrapa Algodão, Campina Grande, Paraíba. The biological responses and thermal requirements of D. echinocacti were evaluated at constant temperatures of 25, 28, 30, 33 and 35 °C, relative humidity of 60 ± 10% and photoperiod of 12 hours in the laboratory. Two experiments were carried out to test the efficacy of sisal extract against cactus scale mealybug. The first aimed to select a concentration of extract from the most promising sisal genotypes to cause mortality in 80% of the population (LC80) of first instar D. echinocacti crawlers nymphs and the second to determine the effectiveness of the selected extract against nymphs, pupae and mealybug adults of different ages in laboratory and greenhouse. The period of development and survival in the stages of egg, nymph and pupa, egg-adult cycle, longevity and fecundity of D. echinocacti in the cladodes of forage cactus varied with the temperatures, being the range of 25°C and 30°C the most favorable for this scale mealybug. The population growth potential of D. echinocacti was higher in the municipalities of Barra de Santana, João Pessoa, Monteiro and Patos, Paraíba, Brazil. The highest number of generations per year of D. echinocacti, estimated for João Pessoa and Patos, indicates that the cultivation of forage cactus should be avoided in these municipalities. The most efficient lethal concentration in causing mortality in 80% of the population of first instar crawlers nymphs of D. echinocacti was obtained for the extract of the sisal genotype A. fourcroydes cv. Cabinho, followed by A. sisalana cv. Tatuí 3. The sisal extract of the genotype A. fourcroydes cv. Cabinho was responsible for causing mortality greater than 74% in nymphs, pupae and adults of different ages of D. echinocacti under laboratory and greenhouse conditions. However, greater effectiveness in causing mortality of this mealybug was obtained after applications with mineral oil alone or in mixture with sisal extract.