Host suitability of different instars of Bemisia tabaci biotype B for the parasitoid Eretmocerus hayati

The incidence of parasitism, host feeding, development time, survivorship, and sex ratio of the parasitoid Eretmocerus hayati Zolnerowich and Rose were evaluated when different nymphal instars of Bemisia tabaci Gennadius biotype B were offered as hosts. Experiments were conducted on tomato at 26 +/- 1 degrees C, 65 +/- 5% RH, and 14:10 (L:D) photoperiod. Er. hayati successfully oviposited and host-fed on all nymphal instars of B. tabaci on tomato with the exception of late fourth instars. However, the number of parasitized early fourth instars (4.4 nymphs female(-1) day(-1)) was significantly lower than that of first, second, and third instars, and the greatest incidence of parasitism was observed on first instars (10.2 nymphs female(-1) day(-1)), followed by similar number on the second (9.7 nymphs female(-1) day(-1)), and third instars (7.7 nymphs female(-1) day(-1)). The number of first, second, third, and early fourth nymphal instars fed on by females was 14.1, 9.7, 7.5, and 3.3 female(-1) day(-1), respectively. Development time of Er. hayati was longest when first instars (17.4 days) were parasitized, intermediate for the second (16.3 days), and third (14.2 days) instars, and shortest for the early fourth (13.5 days) instars. The difference of development time between female and male was not significant. Survivorship (75.2%) did not differ statistically for parasitoids developing in whiteflies that were parasitized as different instars but offspring sex ratio (female/male) varied from 0.94 to 1.43. These values are well above those reported for other B. tabaci parasitoids, indicating that Er. hayati is a good candidate for biological control of B. tabaci in China. (C) 2011 Elsevier Inc. All rights reserved.