The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) causes serious crop losses worldwide by transmitting viruses. We have previously shown that salicylic acid (SA)-related plant defenses directly affect whiteflies. In this study, we applied exogenous SA to tomato plants in order to investigate the interaction between SA-induced plant volatiles and nonviruliferous B. tabaci B and Q or B- and Q-carrying tomato yellow leaf curl virus (TYLCV). The results showed that exogenous SA caused plants to repel nonviruliferous whiteflies, but the effect was reduced when the SA concentration was low and when the whiteflies were viruliferous. Exogenous SA increased the number and quantity of plant volatiles—especially the quantity of methyl salicylate and δ-limonene. In Y-tube olfactometer assays, methyl salicylate and δ-limonene repelled the whiteflies, but the repellency was reduced for viruliferous Q. We suggest that the release of plant volatiles as mediated by SA affects the interaction between whiteflies, plants, and viruses. Further studies are needed to determine why viruliferous Q is less sensitive than nonviruliferous Q to repellent plant volatiles.

Although the cotton bollworm Helicoverpa armigera has traditionally been controlled by application of chemical pesticides, chemical control selects for resistance, pollutes the environment, and endangers human health. New methods for controlling H. armigera are therefore needed. Heliothis virescens ascovirus 3i (HvAV-3i) is a recently identified virus of lepidopteran larvae. We tested the effects of HvAV-3i on H. armigera larvae following oral ingestion of HvAV-3i-containing hemolymph (about 1.0×1010 virus genome copies per larvae) and following injection of HvAV-3i-containing hemolymph by insertion of a needle. Following oral ingestion, first-instar to fifth-instar larvae grew and developed normally. Following needle injection, in contrast, the corrected mortality of third- and fourth- instars was 88.9 ± 2.1% and 93.7 ± 3.4%, respectively. Food intake was significantly lower for larvae injected with virus-containing hemolymph than with virus-free hemolymph. Larvae injected with virus-containing hemolymph had extended survival times and could not complete the pre-pupal stage. These results indicate that inoculation of HvAV-3i via needle injection but not via oral ingestion significantly reduced the growth and development of H. armigera larvae.

Plants respond to herbivorous insect attacks by releasing volatiles that directly harm the herbivore or that indirectly harm the herbivore by attracting its natural enemies. Although the larvae of Spodoptera litura (the tobacco cutworm) are known to induce the release of host plant volatiles, the effects of such volatiles on host location by S. litura and by the parasitoid Microplitis similis, a natural enemy of S. litura larvae, are poorly understood. Here, we found that both the regurgitate of S. litura larvae and S. litura-infested cabbage leaves attracted M. similis. S. litura had a reduced preference for cabbage plants that had been infested with S. litura for 24 or 48 h. M. similis selection of plants was positively correlated with the release of limonene; linalool and hexadecane, and was negatively correlated with the release of (E)-2-hexenal and 1-Butene, 4-isothiocyanato. S. litura selection of plants was positively correlated with the release of (E)-2-hexenal, 1-Butene, 4-isothiocyanato, and decanal, and was negatively correlated with the release of limonene, nonanal, hexadecane, heptadecane, and octadecane. Our results indicate that host plant volatiles can regulate the behavior of S. litura and M. similis.

The pathogenicity of a virus to a specific host species is an inerratic and describable ability of a virus to cause infection but is generally shaped by a variety of abiotic and biotic factors. In this investigation, the variations in pathogenicity of Heliothis virescens ascovirus 3h (HvAV-3h) to five noctuid pests were assessed based on mass spectrometry analysis on the virion compositions. Twenty-nine common HvAV-3h proteins were shared across all hosts, and different flexible proteins were identified in the virions of each specific host. Different host proteins were identified as HvAV-3h virion-associated proteins, including different detoxification enzyme proteins. Furthermore, a relatively fixed relationship between viral replication and changes in host detoxification enzyme activity caused by deficiencies in various viral structural proteins was found in the host larvae using a correlation matrix analysis: the host larval carboxylesterase and cytochrome P450 monooxygenases generally had highly similar responses to the viruses blocked by different structural proteins’ antisera and their effects on viral DNA replication. Different interaction patterns for the virion structural proteins were found in different host larvae-produced virions, and the interactions between Spodoptera litura glutathione S-transferases and viral structural proteins were confirmed. The different host responses after viral infection could be the reason for the changes in viral pathogenicity, while the virus responses gradually adapted to the different hosts and there were flexible changes in the virion structures. IMPORTANCE: Different pathogenic processes of a virus in different hosts are related to the host individual differences, which makes the virus undergoes different survival pressures. Here, we found that the virions of an insect virus, Heliothis virescens ascovirus 3h (HvAV-3h), had different protein composition when they were purified from different host larval species. These “adaptive changes” of the virions were analyzed in detail in this study, which mainly included the differences of the protein composition of virions and the differences in affinity between virions and different host proteins. The results of this study revealed the flexible changes of viruses to help themselves adapt to different hosts. Also, these interesting findings can provide new insights to improve our understanding of virus adaptability and virulence differentiation caused by the adaptation process.