Interactive Effects of an Herbivore-Induced Plant Volatile and Color on an Insect Community in Cranberry

Evaluation of olfactory and visual cues for conservation biological control of crape myrtle bark scale in urban landscapes

BACKGROUND

Acanthacoccus lagerstroemiae (crape myrtle bark scale, CMBS) is an exotic scale insect that feeds on the sap of crape myrtle trees. Heavy infestations of CMBS reduce flowering and honeydew promotes sooty mold growth on the leaves and branches, reducing the aesthetic value of crape myrtle trees in urban landscapes. Lady beetles (Coleoptera: Coccinellidae) are generalist predators that feed on CMBS. Several laboratory and field studies have demonstrated the attraction of lady beetles to olfactory and visual cues. We evaluated lady beetles' responses to olfactory lures and yellow visual attractants on infested potted and landscape trees to increase natural enemy recruitment and reduce dependence on chemical control methods.

RESULTS

Gas chromatography mass spectrometry analysis showed that limonene is the dominant volatile compound released by crape myrtles infested with CMBS. Limonene and methyl salicylate lures, alone or in combination, failed to reduce CMBS or recruit additional lady beetles to infested trees in all experiments. Yellow rectangular panels placed 1 m above the base of an infested tree recruited up to twofold more lady beetles than control trees; however, this was not statistically significant. A significant reduction in CMBS was observed on infested trees with yellow rectangular panels placed in the canopy.

CONCLUSION

Yellow rectangular panels are more likely to recruit lady beetles than limonene or methyl salicylate lures in an urban landscape. Management of CMBS is currently achieved using systemic insecticides. This study provides a basis for conservation biological control of CMBS through the recruitment of lady beetles, a significant advancement toward integrated management of this exotic pest. © 2024 Society of Chemical Industry.

The Role of Green Gram Plant Volatile Blends in the Behavior of Arctiid Moth, Spilosoma obliqua

This study investigated effects of volatile blends released from undamaged (UD), insect-damaged [ID, plants fed by larvae of Spilosoma obliqua Walker (Lepidoptera: Arctiidae)] and mechanically-damaged (MD) plants of three green gram cultivars [PDM 54, Pusa Baisakhi and Samrat] including synthetic blends on the behavior of conspecific adult moths in Y-tube olfactometer bioassays. Females showed attraction towards volatile blends of UD, ID and MD plants of these green gram cultivars against the control solvent (CH₂Cl₂). The components of volatile blends in UD plants of three green gram cultivars are not similar, but no any difference was found among three cultivars in term of the attractive effect on the insect moths when volatile blends from UD plants of these three cultivars were tested against one another. Females were more attracted towards volatile blends of ID plants of a particular cultivar compared to UD plants of the same cultivar. Total amount of volatiles was higher in ID plants than UD plants. Some herbivore-induced plant volatiles - (Z)-3-hexenal, 1-hexanol, (Z)-3-hexenyl acetate, 2-octanol and ocimene were attractive to the insect moths. Females were attracted towards three synthetic blends resembling amounts present in natural volatile blends of ID plants of these three cultivars in Y-tube olfactometer and wind tunnel bioassays, suggesting that involvement of host-specific chemical cues in long-range host location by S. obliqua females. If attraction of adult S. obliqua to these synthetic volatile blends is upheld by field trials then these blends may find practical application in detection and monitoring of S. obliqua populations.

Behavioral Response of Halyomorpha halys (Hemiptera: Pentatomidae) and Its Egg Parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae) to Host Plant Odors

Insects use a range of cues to help them interact with each other and their host plants. Among these cues, olfaction plays a major role in host selection. The present study investigated the behavioral response of the brown marmorated stink bug, Halyomorpha halys (Stål), and its egg parasitoid, Trissolcus japonicus (Ashmead), to host plant-related odors. We used H. halys nymphs since their response to host odors is relatively unknown. In a Y-tube, we first evaluated the behavioral response of H. halys nymphs to whole-fruit odors of apple [Malus domestica (Borkh.)] and peach [Prunus persica (L.) Batsch)]. Subsequently, we tested the behavioral response of H. halys and T. japonicus to 18 selected synthetic volatiles previously identified from H. halys and its common host plants. In the greenhouse, we further tested H. halys attraction to the most promising of these volatiles individually and as blends. In single-choice tests, H. halys nymphs preferred odors from apple and peach over the control (no odor). In dual-choice tests, H. halys did not show any preference between apple and peach odors. Among the 18 volatiles tested, H. halys nymphs were attracted to ethyl salicylate (ES), undecane (UN), and ethyl acetate (EA) compared to the control. In the greenhouse, H. halys nymphs were similarly attracted to blends of 1:1 ratio of ES and EA but not to single compounds. Also in the Y-tube, female T. japonicus preferred the arm that had ES, β-caryophyllene, and decanal and a blend of these three compounds at a 1:1:1 ratio. Trissolcus japonicus was more attracted to the control arm than to the arm containing tridecane or α-pinene. These results indicate the potential of developing H. halys and T. japonicus attractants or/and repellents based on host plant volatiles and suggest possible adaptive responses of this pest and its egg parasitoid to similar host plant odors.