Tetrastichus howardi (Hymenoptera: Eulophidae) in Different Densities and Periods of Parasitism on Diatraea saccharalis (Lepidoptera: Crambidae) Caterpillars

摘要

It is important to determine the suitability of parasitoid density and the parasitism period to obtain the desired number and quality of parasitoid offspring. The aim of this study was to establish the parasitism, emergence, number of progeny, duration of the life cycle (egg to adult), and sex ratio of Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) with two parasitoid densities and eight parasitism periods on third-instar Diatraea saccharalis (F.) (Lepidoptera: Crambidae) caterpillars. Each caterpillar of this host was exposed to one or three T. howardi females for different periods of time (0.016, 0.5, 1, 12, 24, 48, 72, and 96 h) in plastic glass (100 ml). The parasitized hosts were transferred to glass tubes (8.5 cm in height by 2.5 cm in diameter) with an artificial diet and were placed in a climatic chamber at 25 +/- 2 degrees C, 70 +/- 10% relative humidity, and a photoperiod of 14:10 (L:D) h until the emergence of adult parasitoids. T. howardi parasitized and developed in D. saccharalis caterpillars at all the female densities and parasitism periods tested. The emergence and progeny of T. howardi increased with the length of the parasitism period. The shortest life cycle (egg to adult) of T. howardi was 17.00 d at a density of 3:1 and 12 h of parasitism. The parasitism, emergence, and number of T. howardi progeny were highest at a density of 3:1 and at 96 h of parasitism on D. saccharalis third instars