Functional response of Harmonia axyridis preying on Acyrthosiphon pisum nymphs: the effect of temperature

In the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h−1 and 0.25 ± 0.015 h−1; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

Temperature-Dependent Functional Response of Harmonia Axyridis Pallas (Coleoptera: Coccinellidae) Preying on Acyrthosiphon Pisum (Harris) (Hemiptera: Aphididae) Nymphs

Functional response models are often used to understand the foraging interactions and determine the suitable biocontrol agents. We determined the functional response of Harmonia axyridis to nymph Acyrthosiphon pisum at different but constant temperatures (between 15 and 35 °C) and prey densities. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to different densities of A. pisum. Warming increased both the predation activity and host aphid control mortality. The 4th instar and female H. axyridis consumed the most aphids. Warming contributed markedly in accelerating the predator action. For fourth instar larvae and female H. axyridis adult, the successful attack rates were 0.234 ± 0.014 h−1 and 0.247 ± 0.015 h−1; the handling times were 0.132 ± 0.005 h and 0.156 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further studies exploring intraguild predation and mutual interference will be required to conclude the biocontrol potential of H. axyridis to A. pisum.

Comparative analysis of the demographic parameters of seven spotted ladybird beetle (Coleoptera: Coccinellidae) reared on various host aphid species

Background The demographic parameters of the predacious seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera: Coccinellidae) reared on the following four host aphid species were compared: Rhopalosiphum padi Linnaeus (Hemiptera: Aphididae), Rhopalosiphum maidis Fitch (Hemiptera: Aphididae), Sitobion avenae Fabricius (Hemiptera: Aphididae), and Schizaphis graminum Rondani (Hemiptera: Aphididae). Methods The developmental period, fecundity, adult preoviposition period, total preoviposition period and population parameters were evaluated based on the two-sex age-stage life table. The duration of the developmental stages and the population parameters were calculated with the TWOSEX-MSChart program, whereas population size was projected based on the two-sex age-stage life table data with the TIMING-MSChart program. Results The intrinsic rate of increase (r) was the highest in the R. padi predators (0.1946 per day), followed by the S. graminum (0.1435 per day), S. avenae (0.1400 per day), and R. maidis (0.1180 per day) predators. The differences in the net reproductive rate (R0) and the finite rate of increase (λ) when C. septempunctata was reared on the four aphid species were consistent with the r values. This trend was reversed for the mean generation time (T), which ranged from 29.02 days for the lady beetles reared on R. padi to 39.75 days for the lady beetles reared on R. maidis. Interestingly, R. padi was the most suitable host, while the congeneric R. maidis was the least suitable. The results of this study may be useful for future investigations regarding the ecological effects of predatory species and the mass-production of C. septempunctata in the laboratory for an augmentative release of an aphid predator.

A Symbiotic Virus Facilitates Aphid Adaptation to Host Plants by Suppressing Jasmonic Acid Responses

Symbiotic viruses exist in many insects; however, their functions in host insects are not well understood. In this study, we explored the role of acyrthosiphon pisum virus (APV) in the interaction of its host aphid Acyrthosiphon pisum with plants. APV is primarily located in aphid salivary glands and gut and propagated in the insect. APV is horizontally transmitted to host plants during aphid feeding, but the virus does not replicate in the host plant. When the pea host race of aphids colonized two low-fitness plants, Medicago truncatula and Vicia villosa, the virus titers in both the aphids and plants significantly increased. Furthermore, APV infection strongly promoted the survival rate of the pea host race on V. villosa. Transcriptomic analysis showed that only 0.85% of aphid genes responded to APV infection when aphids fed on V. villosa, with a fold change in transcript levels of no more than fourfold. The improved survival due to APV infection was apparently related to the inhibitory effect of the virus on levels of phytohormone jasmonic acid (JA) and JA-isoleucine. Our data suggest a benefit of the symbiotic virus to its aphid host and demonstrate a novel case of symbiotic virus-mediated three-species interaction.

Review of Aphidiinae parasitoids (Hymenoptera: Braconidae) of the Middle East and North Africa: key to species and host associations

In this study, a total of 108 Aphidiinae species, belonging to 18 genera, associated with 240 aphid species in 16 countries of the Middle East and North Africa are reviewed. 743 host aphid-parasitoid associations are listed. New material was collected from various regions of Saudi Arabia during 2011–2013. Three species including Aphidius avenae Haliday, 1834, Aphidius platensis Brèthes, 1913 and Praon barbatum Mackauer, 1967 are first recorded for the fauna of this country. Lysiphlebus marismortui Mescheloff & Rosen, 1990 syn. nov. is classified as the junior synonym of Lysiphlebus confusus Tremblay & Eady, 1978. An illustrated up-to-date key to all known species of Aphidiinae that occur in the Middle East and North Africa is provided. The findings are discussed in relation to the overall parasitoid-aphid associations in the target investigated region.