Host-Finding Behavior of Dinoderus bifoveolatus (Coleoptera: Bostrichidae), an Important Pest of Stored Cassava: the Role of Plant Volatiles and Odors of Conspecifics

Abstract The diamondback moth (Plutella xylostella, DBM) is an important pest of cruciferous vegetables. The use of chlorantraniliprole has been essential in the management of the DBM. However, in many countries and areas, DBM has become highly resistant to chlorantraniliprole. Three different DBM strains, susceptible (S), chlorantraniliprole-selected (Rc), and field-collected (Rb) resistant strains/populations were studied for the role of phenoloxidase in resistance development to the insecticide. By assaying the activity of phenoloxidase (PO) in the three different DBM strains, the results showed that the PO activity in the Rc strain was increased significantly compared with the S strain. The synergistic effects of quercetin showed that the resistant ratio (RR) of the QRc larvae to chlorantraniliprole was decreased from 423.95 to 316.42-fold compared with the Rc larvae. Further studies demonstrated that the transcriptional and translational expression levels of PxPPO1 (P. xylostella prophenoloxidase-1 gene) and PxPPO2 (P. xylostella prophenoloxidase-2 gene) were increased to varying degrees compared with the S strain, such as the transcriptional expression levels of PxPPO2 were 24.02-fold that of the S strain. The responses of phenoloxidase were significantly different in chlorantraniliprole-resistant DBM.

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Do plant volatiles confuse rather than guide foraging behavior of the aphid hyperparasitoid Dendrocerus aphidum?

Chemoecology ◽

10.1007/s00049-020-00321-5 ◽

2020 ◽

Vol 30 (6) ◽

pp. 315-325

Author(s):

Jetske G. de Boer ◽

Petra J. Hollander ◽

Daan Heinen ◽

Divya Jagger ◽

Pim van Sliedregt ◽

...

Keyword(s):

Foraging Behavior ◽

Plant Volatiles ◽

Sweet Pepper ◽

Trophic Levels ◽

Plant Host ◽

Olfactory Responses ◽

Clean Air ◽

Series Of Experiments ◽

Pepper Plants

Abstract Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior.

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Characterization and Expression of Genes Encoding Superoxide Dismutase in the Oriental Armyworm, Mythimna separata (Lepidoptera: Noctuidae)

Journal of Economic Entomology ◽

10.1093/jee/toz163 ◽

2019 ◽

Vol 112 (5) ◽

pp. 2381-2388 ◽

Cited By ~ 1

Author(s):

Hong-Bo Li ◽

Chang-Geng Dai ◽

Yong-Fu He ◽

Yang Hu

Keyword(s):

Superoxide Dismutase ◽

Population Density ◽

Developmental Stages ◽

Mythimna Separata ◽

Expression Of Genes ◽

Genes Encoding ◽

Key Factor ◽

Important Pest ◽

Oriental Armyworm

Abstract Superoxide dismutase (SOD) is an antioxidant metalloenzyme that catalyzes the dismutation of the superoxide anion O2− to O2 and H2O2. Many studies have focused on the role of SOD in response to abiotic stress, but its role during biotic stress, such as changes in organismal population density, has rarely been investigated. The oriental armyworm, Mythimna separata, is an economically important pest that exhibits phenotypic changes in response to population density. Solitary and gregarious phases occur at low and high population density, respectively. To examine the role of SODs in response to population density stress, we cloned two genes encoding SOD, MsCuZnSOD and MsMnSOD, and compared their expression in solitary and gregarious phases of M. separata. The MsCuZnSOD and MsMnSOD ORFs were 480 and 651 bp and encoded predicted protein products of 159 and 216 amino acids, respectively. The two SODs contained motifs that are typical of orthologous proteins. Real-time PCR indicated that the two SOD genes were expressed throughout developmental stages and were significantly upregulated in more mature stages of gregarious M. separata. Expression of the two SOD genes in various tissues of sixth-instar larvae was higher in gregarious versus solitary insects. Furthermore, expression of the SOD genes was significantly upregulated in response to crowding in solitary individuals, but suppressed in gregarious insects subjected to isolation. Collectively, these results suggest that population density may be key factor in the induction of SOD genes in M. separata.

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