Efficacy of Trunk Trap Nets and Insecticides Applied Alone and in Combination for Control of Tree-of-heaven Root Weevil Eucryptorrhynchus scrobiculatus in Ailanthus altissima Plantations

Multiple factors influenced the aggregation behavior of adult Eucryptorrhynchus scrobicuatus (Coleoptera: Curculionidae)

Eucryptorrhynchus scrobiculatus (Motschulsky) (Coleoptera: Curculionidae) is a notorious pest of Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae). E. scrobiculatus adults typically aggregate under leaves and in soil crevices at the base of A. altissima in the field. We hypothesize that the environmental factors and conspecific signals determine their aggregation behavior. To test this, we investigated adult numbers in light-exposed and shaded areas of the sample trees and conducted experiments in both field and lab settings. Results revealed that (i) greater adult distribution in shaded areas; (ii) significant influence of temperature and illumination on aggregation tendency in the field; (iii) no gender-based difference in aggregation degree and maximum aggregation between light and dark; (iv) the host plant triggering the aggregation tendency, negatively affected in the absence; (v) the aggregation tendency of E. scrobiculatus weakened with the temperature gradually changing to ordinary temperature; and (vi) mutual attraction and chemical attraction between males and females. Thus, the aggregation behavior was influenced by factors including temperature, light intensity, host plant, and conspecific signals, but light's role was not obvious in the lab.

A new management tactic for Eucryptorrhynchus scrobiculatus (Coleoptera: Curculionidae) based on factors influencing the weevil population density

BACKGROUND

The tree of heaven root weevil, Eucryptorrhynchus scrobiculatus (TRW), is one of the most damaging pests of Ailanthus altissima in China. A limited number of studies have examined the effects of different variables on the population density of TRW adults. We investigated the relative impacts of the diameter at breast height of host trees (DBH), number of tree species in plots (NTS), weed coverage rate of the host tree base (WCR), plot area (PA), distance from plots to the nearest farmland (DNF), nearest human community (DNHC), nearest irrigation canal (DNIC), and nearest road (DNR) on TRW population density. We then evaluated the effect of removing weeds at the base of the tree trunk (RW) on TRW population density.

RESULTS

We found that DBH, WCR, PA, and DNHC significantly affected the population density of TRW adults, whereas NTS, DNF, DNIC, and DNR did not. Adult TRW density was positively correlated with DBH, WCR, and PA but was negatively correlated with DNHC. Further field trials showed that RW treatments significantly reduced the density of adult TRW (an average annual reduction of 51.7% compared to untreated trees).

CONCLUSION

This information on the factors affecting the population density of TRW promoted the development of new TRW management strategies. Our results demonstrate that RW is an effective method for reducing the population density of TRW adults. Therefore, this new physical method using RW could be recommended as an alternative for TRW management in the framework of integrated pest management. © 2021 Society of Chemical Industry.

Developing traps for the overwintering tree-of-heaven weevils Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae)

BACKGROUND

The tree-of-heaven root and trunk weevils, Eucryptorrhynchus scrobiculatus (TRW) and E. brandti (TTW) are important boring pests of Ailanthus altissima in China. Overwintering TRW and TTW adults can continue to damage A. altissima trees and reproduce after they emerge from the soil each year. There is a lack of studies regarding the development of control measures during the overwintering period. A polyethylene terephthalate bottle trap (PETBT) and corrugated paper box trap (CPBT) were evaluated for their ability to trap TRW and TTW adults descending from trees to overwinter in the soil in Wutongshu and Shabatou locations in Ningxia, China.

RESULTS

Significantly more overwintering TRW adults were caught by the PETBT than the CPBT. There were no significant differences in the TTW captures in PETBT when compared to the CPBT. Both PETBT and CPBT have little effect on trapping overwintering TTW adults. Further trapping studies showed that PETBT treatments significantly reduced overwintering TRW numbers caught in population monitoring trap nets placed on the A. altissima tree trunks (an average annual reduction of 42% than the untreated trees).

CONCLUSION

These results demonstrate that PETBT is effective for trapping overwintering TRW adults. PETBT could be recommended as an alternative for managing TRW in the framework of integrated pest management. © 2021 Society of Chemical Industry.

Contrasting Behavioral and Electrophysiological Responses of Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae) to Volatiles Emitted from the Tree of Heaven, Ailanthus altissima

Simple Summary

Eucryptorrhynchus scrobiculatus (Motschulsky) and E. brandti (Harold) are significant pests of tree of heaven, Ailanthus altissima, often leading to tree death. Monitoring systems that involve host–plant based attractants need to be developed for both insect pest species. Here, we compared the behavioral and electrophysiological responses of E. scrobiculatus and E. brandti to volatiles emitted by various parts of the host plant. Host plant-derived volatiles showed to play a greater role in the foraging behavior of E. brandti than in E. scrobiculatus. Volatile components of phloem were found to be particularly attractive to E. brandti.

Abstract

Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae) are host-specific pests of Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae), causing extensive damage to the host. There are no effective attractants available for pest management. The main aim of this study was to explore the role of host plant-derived volatiles in the behavioral response of both weevil species. In a field experiment, both weevil species showed positive response to phloem, and there was no preference for phloem associated with healthy or injured trees. Significantly more E. brandti adults responded to the olfactory treatments compared to E. scrobiculatus. In a large-arena experiment, both males and females of E. scrobiculatus significantly preferred phloem from the tree trunk while adults of E. brandti responded in significantly greater numbers to tree limbs than to any other parts of host. Females and males of E. scrobiculatus responded positively to all parts of host tested in the Y-tube bioassay, while E. brandti adults were only attracted by the phloem from healthy and injured trees. There were dissimilar electroantennographic responses to compounds such as 1-hexanol and (1S)-(−)-β-pinene between the two weevil species. This study represents the first report documenting behavioral and electrophysiological responses of E. scrobiculatus and E. brandti to volatiles from various parts of A. altissima and findings may aid efforts to develop attractants.