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.

BACKGROUND Resistance to insect pests is an important self‐defense characteristic of pepper plants. However, the resistance of different pepper cultivars to Spodoptera litura larvae, one of the main insect pest species on pepper, is not well understood. RESULTS Among seven pepper cultivars evaluated, cayenne pepper ‘FXBX’ showed the highest repellency to third instar S. litura larvae, Chao tian chili pepper ‘BLTY2’ showed the lowest repellency. Plant volatiles (1‐hexene, hexanal, β‐ionone, (E,E)‐2,6‐nonadienal, and methyl salicylate) affected host selection by S. litura. Among these, 1‐hexene, hexanal, and β‐ionone at concentrations naturally‐released by pepper leaves were found to repel S. litura. Interestingly, S. litura larvae fed on the larva‐attracting pepper cultivar, (BLTY2) had an extended developmental period, which was about 13 days longer than larvae fed on FXBX. Besides, the survival rate of larvae fed on BLTY2 was 22.5 ± 0.0%, indicating that the leaves of BLTY2 can kill S. litura larvae. Correlation analysis showed that larval survival rate, emergence rate, female adult longevity, and pupal weight were positively correlated with the vitamin C, amino acids, protein, cellulose, and soluble sugar contents, but were negatively correlated with wax and flavonoids contents. CONCLUSION We identified two different modes of direct defense exhibited by pepper cultivars against S. litura. One involves the release of repellent volatiles to avoid been fed on (FXBX cultivar). The other involves the inhibition of the growth and development or the direct killing of S. litura larvae which feeds on it (BLTY2 cultivar). © 2022 Society of Chemical Industry.

Background Herbivore‐induced plant volatiles (HIPVs) are important self‐defense outputs of pepper plants to resist insect pests. Ascoviruses are pathogenic to the larvae of most lepidopteran vegetable pests. However, whether Heliothis virescens ascovirus 3h (HvAV‐3h)‐infected Spodoptera litura larvae can change pepper leaf HIPVs is not well understood. RESULTS Spodoptera litura larvae preferred S. litura‐infested leaves, and this preference was stronger with longer duration of S. litura infestation. In addition, S. litura larvae significantly chose pepper leaves damaged by HvAV‐3h‐infected S. litura over the healthy pepper leaves. Results also showed that S. litura larvae preferred leaves mechanically damaged and treated with oral secretions from HvAV‐3h infected‐S. litura larvae in a simulation test. We captured the volatiles emitted by leaves under six treatments. Results showed that the volatile profile changed with the different treatments. Testing of volatile blends, prepared to the proportion released showed that the blend from simulated HvAV‐3h‐infected S. litura larvae‐damaged plants was the most attractive to S. litura larvae. Further, we also found that some of the compounds significantly attracted S. litura larvae at specific concentrations. CONCLUSION HvAV‐3h‐infected S. litura can alter the release of HIPVs in pepper plants and thus become more attractive to S. litura larvae. We speculate that this may be due to alterations in the concentration of some compounds (such as geranylacetone and prohydrojasmon) affecting the behavior of S. litura larvae. © 2023 Society of Chemical Industry.

Vectors of viruses and other plant pathogens are known to often be attracted by pathogen-infected plants, which promotes pathogen spread. However, few studies have examined how virus-induced changes in plant volatiles mediate such preference. Previous research has demonstrated that tomato plants become more attractive to the whitefly Bemisia tabaci when they are infected by the begomovirus Tomato yellow leaf curl virus (TYLCV). In the current study, we found that the increase in attractiveness is associated with TYLCV-repressed terpenoid synthesis in the virus-infected plants. The observed TYLCV suppression of terpenoid synthesis is similar to the suppression of terpenoid synthesis induced by whitefly infestation. Secondary metabolite analyses and olfactometer experiments with mutant plants revealed that a reduced release of terpenoids through TYLCV-induced suppression of flavonoid synthesis causes B. tabaci females to prefers TYLCV-infected plants over non-infected plants. These results show that TYLCV infection triggers the same changes in odor signaling as caused by B. tabaci infestation, such that both B. tabaci infestation and TYLCV infection increase whitefly aggregation and thereby increase vector acquisition and spread of TYLCV.

The complete mitochondrial genome (mitogenome) of Lyssa zampa was first reported. It is 15,314 bp in length (GenBank accession number: MW435592) and consists of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes. The nucleotide composition is A (41.5%), C (11.1%), G (7.4%), and T (40.0%). Based on the sequences of complete mitogenome from 12 geometroid species and three drepanoid species as ingroups, and two noctuoid species as outgroups, the phylogenetic tree was constructed. The results showed that the closest relationship between Uraniidae and Epicopeiidae was strongly supported by Bayesian posterior probabilities values of 0.99.