Life History Parameters and Temperature Requirements for Development of an Aphid Parasitoid <I>Aphelinus asychis</I> (Hymenoptera: Aphelinidae)

Abstract

We assessed the life history parameters and temperature requirement of a Korean population of the endoparasitoid Aphelinus asychis Walker (Hymenoptera: Aphelinidae), using Aphis gossypii Glover (Hemiptera: Aphididae) as a host. We Þrst measured the time from egg to mummiÞcation (i.e., pupation) and mummiÞcation to adult emergence (i.e., pupal period) at 25ЊC. The pupal period was signiÞcantly longer than the egg to pupation period in both genders, unlike in other regional populations of the species. Females produced an average of 342.9 mummies, the highest reported fecundity among the various regional populations of this species. Age-speciÞc realized fecundity peaked between the 4th and 7th day (23.3Ð24.8 mummies a day). The intrinsic rate of increase (r m ) was 0.255 offspring per female per day. The parasitoids were then reared at eight constant temperatures between 15 and 32.5ЊC. The developmental time from egg to adult emergence decreased from 27.8 to 9.8 d. The lower developmental thresholds (T 0 ), estimated by linear regression, for the egg to mummy, mummy to adult, and egg to adult stages were 6.7, 6.8 and 6.7, respectively. The thermal constants for each of the three periods were 115, 126, and 243 DD. We compared these parameters with published data of A. asychis from other regions reared on different hosts and representative species of aphid parasitoids in Aphidiinae (Braconidae) reared on hosts including A. gossypii. The T 0 Õs of A. asychis were higher than those of Aphidius colemani and Aphidius matricariae when using A. gossypii.

Temperature-Dependent Demographic Characteristics and Control Potential of Aphelinus asychis Reared from Sitobion avenae as a Biological Control Agent for Myzus persicae on Chili Peppers

“…In this study, the r of A. asychis in the 24 and 28 • C treatments were significantly greater than those in the 20 and 32 • C treatments, which suggested that increasing the temperature benefited the r, but a further increase in temperature negatively affected the population parameter. The r of A. asychis feeding on A. gossypii nymphs was 0.255 at 25 • C [55], which was much greater than that at 20 to 32 • C in our study. The differences between the two studies might be influenced by the host species and temperature.…”

“…The proportions of A. asychis that parasitized 1-2-day-old and 4-5-day-old A. gossypii nymphs and adults were 47.4%, 41.2%, and 47.7%, respectively [53]. Additionally, the proportion of female adults produced by A. asychis parasitizing a combination of second and third instar A. gossypii nymphs was 51.9% [55]. The temperature under which the parasitoids are reared may also affect sex ratio.…”

“…[53]. Additionally, the developmental times of the A. asychis female and male from the egg to the adult stage and parasitization of A. gossypii at 25 • C were 13.9 and 13.2 d, respectively [55]. When it parasitized A. gossypii at 20, 25, and 30 • C, the developmental times were 20.6, 14.2, and 13.0 d respectively [56].…”

“…Many biotic and abiotic factors, including the host species, host plant, and temperature, could affect the longevity of A. asychis. For example, the longevity of A. asychis female adults when they parasitized S. graminum, Rhopalosiphum maidis, or Sipha flava was similar with some variation-about 18 days under greenhouse conditions [54], 20 days when they parasitized S. graminum under field conditions [57], 21 days when they parasitized the second and third instar nymphs of A. gossypii at 25 • C [55], and 23 days with second instar nymphs of M. persicae on chili peppers at 25 • C [13]. In this study, we found that increasing the temperature significantly decreased the total longevity of A. asychis, and the adult longevities of the females and males showed similar responses to temperature.…”

“…A. asychis females produced 232.3, 44.7, and 21.1 eggs when they parasitized 1-2-day-old A. gossypii nymphs, adults, and 4-5-day-old nymphs, respectively [53]. When A. gossypii was used as a host, A. asychis females produced an average of 342.9 mummified aphids at 25 • C [55], which was more than that at 24 • C in this study. When it parasitized the second instar nymph of M. persicae on chili peppers at 25 • C, each A. asychis female produced more eggs (414.6) than that (238.6 eggs) recorded at all four constant temperatures in this study [13].…”