Temporal and spatial characteristics of forest pests in China and their association with large-scale circulation indices.

The increase in extreme climate events in recent years has been considered as an important factor affecting forest pests. Understanding the responses of forest pests to climate is helpful for revealing the trends in forest pest dynamics and proposing effective control measures. In this study, the relationship between the dynamics of all forest pests, independent forest diseases, and forest insect pests with the climate was evaluated in China, and the corresponding differences among forest pests, diseases and insect pests were assessed. Based on cross-wavelet transform and wavelet coherence analysis, the influences of teleconnection factors on the relationship between climate and forest pests were quantitatively analyzed to determine the roles of these factors. The results indicate that (i) three types of disasters in most parts of China have decreased from 1979 to 2019, while forest pests and forest insect pests in the southwestern region have increased; (ii) the relationship among Forest Pest Occurrence Area Rate and climate factors such as the Multivariate ENSO index, Southern Oscillation index, Arctic Oscillation (AO), Atlantic Multidecadal Oscillation (AMO), and Sunspot is more significant; (iii) the cycle is short in most regions, with oscillations in 2-4 years bands being the main variation periods of disasters in East, Central, and South China; (iv) There is a significant correlation between climate and disasters in the periods of 2-4 or 8-10 years. The AO, AMO, and Sunspot were important driving factors affecting the relationship between climate and disasters. Specifically, the Sunspot had the greatest impact among these factors.

Pheromone-trapping the nun moth, Lymantria monacha (Lepidoptera: Lymantriidae) in Inner Mongolia, China.

The nun moth, Lymantria monacha L., is one of the most important defoliators of Eurasian coniferous forests. Outbreaks during 2011-2015 in the natural/planted larch, and larch-birch mixed forests of the Greater Khingan Range in Inner Mongolia, China, caused tremendous timber losses from severe defoliation and tree mortality. A series of trapping experiments were conducted in these outbreak areas to evaluate the efficacy of a synthetic species-specific pheromone lure based on the female pheromone blend of European nun moth populations. Our results clearly show that the nun moth in Inner Mongolia is highly and specifically attracted to this synthetic pheromone, with few gypsy moths (Lymantria dispar) captured. Flight activity monitoring of L. monacha male moths using pheromone-baited Unitraps at 2 locations during the summer of 2015 indicated that the flight period started in mid-July, peaking in early August at both locations. Based on male moth captures, there was a strong diurnal rhythm of flight activity throughout the entire scotophase, peaking between 22:00 and 24:00. Unitraps and wing traps had significantly and surprisingly higher catches than the gypsy moth traps. Unitraps fastened to tree trunks 2 m above ground caught significantly more male moths than those at the ground level or at 5 m height. Male L. monacha moths can be attracted to pheromone-baited traps in open areas 150-200 m distant from the infested forest edge. Our data should allow improvement on the performance of pheromone-baited traps for monitoring or mass-trapping to combat outbreaks of this pest in northeastern China.

Catching Ips duplicatus (Sahlberg) (Coleoptera: Scolytidae) with pheromone-baited traps: optimal trap type, colour, height and distance to infestation.

BACKGROUND: Field trapping experiments were carried out to evaluate effective trap characteristics for maximising Ips duplicatus (Sahlberg) catches in pheromone-baited traps in China. RESULTS: Window-slot and cross-barrier traps had significantly higher catches than multiple-funnel traps. The colour of window-slot traps showed a significant effect on catches, with dark colours (black and red) being more effective than light colours, especially white and yellow. Window-slot traps at a 1.5-2.0 m level caught more beetles than those at either ground level (0-0.5 m) or at 3.5-4.0 m. Ips duplicatus can be attracted to pheromone-baited traps over a distance of > 100 m from the forest edge in an open grassy field. There was a strong diurnal pattern of flight activity, with catches on window-slot traps occurring during the daytime with one broad peak at mid- to late afternoon. The seasonal flight activity of I. duplicatus as monitored by pheromone-baited window-slot traps during 2007-2008 indicated that three major flight peaks occurred in early June, late June-early July and late July respectively, suggesting the existence of a potential second generation. CONCLUSION: The optimal trap characteristics will improve the performance of pheromone-baited traps as a critical monitoring or mass-trapping tool to combat outbreaks of this pest species.

Electrophysiological and behavioral responses of Ips subelongatus to semiochemicals from its hosts, non-hosts, and conspecifics in China.

Volatiles from hosts, non-hosts, interspecifics, and conspecifics of the Asian larch bark beetle, Ips subelongatus Motsch., were analyzed using both gas chromatographic-electroantennographic detection (GC-EAD) and gas chromatography/mass spectrometry (GC-MS) techniques, and field trapping bioassays in Inner Mongolia, China. GC-EAD experiments indicated that I. subelongatus antennae (both sexes) strongly responded not only to the major male-produced conspecific components, ipsenol, and ipsdienol, but also to other bark beetle compounds (cis-verbenol and verbenone), host monoterpenes (alpha-pinene, beta-pinene, and para-cymene) from Larix sp. logs, and non-host leaf (green leaf volatiles and geranyl acetone) and bark (C8-alcohols and trans-conophthorin) volatiles. Repeatable EAD responses were also found to two compounds from hindgut extracts that are undetectable by GC. One of these minor compounds was identified as amitinol. Field trapping experiments showed that the EAD-active, major male-hindgut component, racemic ipsenol, is the only individual compound that significantly attracted both sexes of I. subelongatus, whereas all other compounds, including previously reported pheromone components of European Ips cembrae, ipsdienol and 3-methyl-3-buten-1-ol, were unattractive. Ipsdienol, 3-methyl-3-buten-1-ol, or their binary blend had no synergistic or antagonistic effects on I. subelongatus attraction when combined with ipsenol, whereas cis-verbenol (a synomone) and verbenone (the antiaggregation semiochemical) inhibited its attraction to the ipsenol-containing attractive blend. A mixture of three EAD-active host monoterpenes, alpha-pinene, beta-pinene, and para-cymene, was unattractive, but interrupted the pheromone response of I. subelongatus. Geranyl acetone, one of the strong EAD-active non-host volatiles also significantly reduced the number of I. subelongatus captured in traps baited with ipsenol-containing attractive blend. Our results add support to the recent phylogenetic finding that European and Asian larch bark beetles should be regarded as two distinct species: I. cembrae infecting larch in Europe and I. subelongatus infesting larch in Asia.

Iridodial: a powerful attractant for the green lacewing, Chrysopa septempunctata (Neuroptera: Chrysopidae).

The lacewing Chrysopa septempunctata Wesmael is an important, common predator of several insects in China, Japan, Russia, and many parts of Europe. Our field trapping experiments in northeast China showed that males of this green lacewing are strongly attracted to the lacewing pheromone of Chrysopa oculata Say, (1R,2S,5R,8R)-iridodial. The induced plant volatile, methyl salicylate, was unattractive to C. septempunctata by itself at the concentration tested, but synergistic when combined with iridodial where the lacewing population was high. (1R,4aS,7S,7aR)-Nepetalactol and (4aS,7S,7aR)-nepetalactone (aphid sex pheromone components) caught significantly more males of C. septempunctata than did blank control traps, but were inferior to iridodial dispensers, which remained strongly attractive to C. septempunctata males for at least 2.5 months. These results indicate that (1R,2S,5R,8R)-iridodial is a powerful attractant for C. septempunctata, and may have great potential for enhanced biological control of garden, agricultural, and forest insect pests.