Impact of Leptoglossus occidentalis (Hemiptera: Coreidae) on Douglas-fir seed production

We investigated the effect of feeding by the western conifer-seed bug, Leptoglossus occidentalis Heidemann, on seed production in developing cones of coastal Douglas-fir, Pseudostuga menziesii (Mirb.) Franco, with respect to seed bug life stage and sex (nymphs, adult females, and adult males) and timing of feeding (early, mid-, and late season cone development). Feeding by females on caged cones for a 2-wk period during late season cone development reduced the proportion of full seeds in cones by approximately 70% compared with caged control cones. There was no significant difference among nymphs, adult females, and adult males with respect to the proportion of empty or partially fed-upon seeds produced during the same feeding period. Feeding by nymphs for 2 wk early in the season resulted in a threefold increase in the number of unextractable seeds fused to cones compared with the control. Weight measurements of harvested seeds indicated that radiography is an accurate tool to distinguish among Douglas-fir seeds that have sustained light, moderate, or severe damage. Determining the full impact of L. occidentalis on conifer seed production will require the development of a reliable method to distinguish between naturally aborted seeds and seeds emptied through feeding by seed bugs.     

Distribution analysis of Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) in South Korea using climate and host plant ensemble maps

Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) is a notorious pest that causes irreversible damage to coniferous forests in South Korea. However, an effective control strategy is still under development. In this study, we used CLIMEX to analyze the potential distribution of L. occidentalis in relation to climate and host plants in South Korea for the identification of effective control spots. The climate needs of L. occidentalis under current and future climate conditions were analyzed and projected on a map along with the distribution of coniferous forests. The CLIMEX model projected that the area of L. occidentalis distribution would decrease slightly in 2060 compared with that at present. However, it was projected that occurrence in mountainous regions would be sustained, suggesting continued damage to coniferous forests in South Korea.     

New occurrence of the invasive alien leaf‐footed bug Leptoglossus gonagra (Hemiptera: Coreidae) in South Korea

The invasive alien leaf‐footed bug Leptoglossus gonagra (Fabricius 1775), native to the Americas, is herein recorded from South Korea for the first time. Forty nymphs and adults were collected on 22 September 2016 from arable lands of two separate sites. These individuals were identified based on the analysis of morphological characters and cytochrome oxidase c subunit 1 sequences. A neighbor‐joining tree indicated the existence of two clades: Group A from Brazil, and Group B from Asia and Oceania. Mean genetic distance between clades was 8.11%, range 7.60–8.57%. Within clades, mean genetic distance was 0.42% (0.17–0.83%) in Group A and, 0.45% (0.00–0.83%) in Group B. Colonies of 2nd‐final instar nymphs and adults were found, on top of leaves, flowers, fruits, and between the stems of pumpkins (Cucurbita moschata). Nymphs and adults damaged host plants by sucking their leaves, stems, fruits, and buds. After the first discovery in 2016, we were unable to find the bugs again (in 2017–2019). Therefore, the invasion of this species seems to have occurred only temporarily, during the warm season. We suggest that the species may have failed to overwinter as it is normally distributed in regions warmer than Korea. Nevertheless, possible appearances of this species must be continuously monitored as it is a potential pest of various plants cultivated in South Korea.     

我国入侵害虫西部喙缘蝽的溯源分析

本文对我国外来入侵物种西部喙缘蝽Leptoglossus occidentalis Heidemann, 1910进行了溯源分析,依据对国内种群的观察和标本简要描述了其形态特征和生活习性。通过野外采集国内种群标本,提取扩增COI基因序列,结合原产地和国外其他入侵种群的公共序列,构建西部喙缘蝽COI基因数据集,以中国入境口岸对木材的检疫情况为参考,分析西部喙缘蝽的入侵来源。全世界目前已知10种单倍型,中国存在4种。山东青岛种群有H＿8、H＿9和H＿10三种单倍型,其中H＿8与韩国共享,H＿9和H＿10为中国特有单倍型,青岛种群可能部分来自韩国;山东烟台两个采集点的种群都属于H＿2,可能来自北美东部,与青岛种群的入侵来源不同。以上分析表明,我国西部喙缘蝽种群可能来源于多次独立入侵事件,同时在国内发生了小范围的扩散迁移。本研究首次对我国入侵害虫西部喙缘蝽做了溯源分析,为更好地制定规制措施,开展检疫防治工作提供了科学依据。     

Morphological and biological characteristics of the Korean population of Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), an invasive insect pest of conifer cones

In this study, we investigated the morphological and biological characteristics of a serious insect pest of conifer cones, the western conifer seed bug (WCSB), Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), in Korea. WCSB adults shared external morphology with overseas populations, including zig-zag fascia on the coria, dilation of the hind tibiae, and color pattern on the abdominal dorsum. The average body length and width of WCSB adults were 17.20 and 4.85 mm, respectively, in males and 19.05 and 5.55 mm in females. The average body weights were 111.27 and 169.89 mg in adult males and females, respectively. On average, eggs were 2.12 mm long and 1.17 mm wide. The average body lengths of the first- to fifth-instar nymphs were 3.07, 4.76, 8.77, 13.56, and 15.53 mm, respectively. For biological characteristics, developmental durations of the egg and five nymphal instar stages were 8.6, 3.7, 7.6, 5.8, 5.8, and 9.1 days, respectively, in laboratory conditions. Nymphal mortality was 47.5% in total. The average life expectancy of WCSB adults was 58.2 and 63.9 days in males and females, respectively. Oviposition of the adult females started 23.4 days after emergence, and the total number of eggs laid by a single adult female was 68.6 on average. The results of this study offer basic morphological and biological information that can be used to design an effective control strategy to manage the WCSB population in Korea.     

Measuring the impact of Leptoglossus occidentalis (Heteroptera: Coreidae) on seed production in lodgepole pine using an antibody-based assay

We measured the impact of Leptoglossus occidentalis on seed production in lodgepole pine, Pinus contorta variety latifolia Engelmann, using an antibody marker developed to detect residual saliva in fed-on seeds. Nymphs, adult females, and adult males were caged on cones during early, mid- and late season cone development. Individual analysis of 12,887 seeds extracted from 365 cones revealed that 37.3% seeds tested positive for seed bug saliva. The antibody assay was 38 times more effective than radiography at detecting seed bug damage. Radiography can detect partially emptied seed but cannot discriminate between aborted seeds and those emptied by seed bugs. The antibody marker was least sensitive in detecting early season damage compared with mid- and late season damage. We hypothesize that residual saliva in seeds fed on early in the season was either absorbed by the damaged seed or degraded over time. Early season feeding resulted in the greatest number of seeds fused to cone scales and the extraction efficiency for cones exposed to feeding during this time was reduced by 64% compared with control cones. Adding fused seeds to antibody-positive seeds raised the proportion of damaged seeds to 48.3%. At all stages of cone development, adult females were the most destructive life stage, damaging up to two seeds per day late in the season. When seed losses were adjusted to damage per degree-day, female damage was greatest early in the season, while males caused the same amount of damage regardless of cone development period. The results of the antibody assay provide baseline data for developing damage prediction formulae, and establish L. occidentalis as a potentially serious pest in lodgepole pine seed orchards.     

The population ecology of Amorbus Dallas (Hemiptera: Coreidae) species in Australia

Species of Amorbus Dallas (Hemiptera: Coreidae) appear to exhibit a tight link between oviposition preference and nymphal performance: females apparently select vigorous plant modules to facilitate the development of their offspring. Such behaviour suggests that these insects should exhibit population dynamics consistent with the latent classification proposed by Price et al. (1990). While this empirical hypothesis is intuitively appealing it does not appear to incorporate current population dynamics theory. Berryman's ecodynamics (1992) offers the potential to describe a species' population dynamics which is grounded in a quantitative theoretical framework. The population ecology of Amorbus species from Australia is considered in relation to these hypotheses.     

Specific biochemical marker-based techniques for the identification of damage to Douglas-fir seed resulting from feeding by the western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae)

Specific biochemical marker-based techniques were tested for their ability to distinguish between seeds of Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco, that were filled or unfilled (aborted) at maturity and those that were damaged or emptied by the western conifer seed bug, Leptoglossus occidentalis Heidemann. A polyclonal antibody raised against salivary gland extracts from L. occidentalis successfully identified residual salivary proteins on Western blots containing proteins from Douglas-fir seeds that had sustained various degrees of seed bug feeding damage. In a single blind experiment, the polyclonal antibody correctly identified 100% of undamaged control, 97% of unfilled control (aborted), and 98% of seed bug damaged seeds. Polyclonal antibodies raised against insoluble alfalfa crystalloid storage protein (11S globulin) detected the depletion of 11S globulin and the subsequent appearance of its hydrolyzed fragments in the soluble protein fraction of Douglas-fir seeds that were fed-upon by the seed bug. Feeding by L. occidentalis nymphs caused ca. 98% depletion of insoluble protein, but only ca. 53% reduction in the amount of soluble protein in seeds that appeared empty on radiographs. By comparison, unfilled (aborted) seeds contained significantly less insoluble and soluble protein than empty seeds that were fed-upon by L. occidentalis; moreover, no crystalloid (11S globulin) breakdown products were generated. The biochemical markers described in this study are reliable tools that can be used to identify conifer seeds that have sustained light to severe damage from L. occidentalis feeding.     

Life table for Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae) and prediction of damage in lodgepole pine seed orchards

Abstract 1 Fecundity, egg hatch and nymphal survivorship of Leptoglossus occidentalis Heidemann were determined and used to develop a damage prediction formula for seed bugs in lodgepole pine seed orchards. 2 A single overwintered L. occidentalis female may lay up to 80 eggs during early and mid‐season cone development. 3 Up to 83.4% of eggs that were attached to branches with tape hatched successfully, compared with 53.5% of eggs attached to needles with wire. Egg parasitism was only observed in egg masses attached with wire. 4 Egg masses attached with wire suffered approximately 30% mortality from parasitism, primarily by Gryon pennsylvanicum (Ashmead). 5 Approximately 15.1 and 2.5% of first instars survived to adulthood in 2000 and 2001, respectively. Survival of caged nymphs that were protected from predators was 14.5 and 17.8%, respectively. 6 A composite survival table indicated that 9.3% of eggs laid by L. occidentalis are expected to survive to adulthood. 7 Based on previously determined damage estimates for each life stage of feeding during three periods of cone development, a hypothetical density of one seed bug per tree early in the season will result in an expected seed loss of approximately 310 seeds.     

Evaluating potential trap crops for managing leaffooted (Hemiptera: Coreidae) and phytophagous stink bug (Hemiptera: Pentatomidae) species in peaches

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Resumen

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