insects Article Seasonal Captures of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) and the Effects of Habitat Type and Tree Species on Detection Frequency Nicole F. Quinn 1,*, Elijah J. Talamas 2, Tracy C. Leskey 3 and J. Christopher Bergh 1 1 Alson H. Smith Jr. Agricultural Research and Extension Center, Virginia Tech, Winchester, VA 22602, USA; [email protected] 2 Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, FL 32608, USA; [email protected] 3 Appalachian Fruit Research Station, USDA ARS, Kearneysville, WV 25430, USA; [email protected] * Correspondence: [email protected] Simple Summary: Trissolcus japonicus, an important natural enemy of brown marmorated stink bug in Asia, was first detected in the USA in 2014. To investigate when and where T. japonicus is found in the field, yellow sticky traps were deployed in the canopy of tree of heaven growing at the edge of small isolated patches, windbreaks, and woodlots in 2018 and 2019. In both years, captures occurred from May to September, with peaks in July and August. Captures of T. japonicus were recorded from all three habitats but were not consistently associated with a particular habit. In 2017 and 2018, T. japonicus captures were compared between tree of heaven paired with several other H. halys host trees growing at the woods edge, and in 2019, captures in tree of heaven, black walnut, and black locust growing in the same windbreaks were compared. Trissolcus japonicus and several native H. halys parasitoids were captured in all hosts, but there was not a consistent effect of host tree species Citation: Quinn, N.F.; Talamas, E.J.; on T. japonicus captures. These results can be used to inform and optimize future surveillance efforts Leskey, T.C.; Bergh, J.C. Seasonal for detecting T. japonicus as it continues to expand its range in the USA. Captures of Trissolcus japonicus (Ashmead) (Hymenoptera: Abstract: Trissolcus japonicus, an important egg parasitoid of Halyomorpha halys in Asia, was first Scelionidae) and the Effects of Habitat detected in the USA in 2014. To evaluate the effect of habitat and the seasonality of T. japonicus Type and Tree Species on Detection detections in the USA, yellow sticky traps were placed in the canopy of Ailanthus altissima growing Frequency. Insects 2021, 12, 118. https://doi.org/10.3390/ at the edge of isolated patches of trees, windbreaks, and woodlots in northern Virginia in 2018 and insects12020118 2019. In both years, captures occurred from May to September, and peaked in July and August. While T. japonicus was detected in all habitats, there was not a consistent effect of habitat type on Received: 17 December 2020 capture frequency. To evaluate tree species effects on T. japonicus captures, in 2017 and 2018, yellow Accepted: 22 January 2021 sticky traps deployed in the canopy of A. altissima bordering apple orchards were paired with a Published: 29 January 2021 nearby trap in one of several wild tree species along a common woods edge. In 2019, these traps were deployed in A. altissima, black walnut, and black locust growing in the same windbreaks. Publisher’s Note: MDPI stays neutral No consistent association between captures of T. japonicus or native parasitoids of H. halys and with regard to jurisdictional claims in the tree species sampled was observed among years. Results are discussed in relation to the ecology published maps and institutional affil- and sampling optimization of T. japonicus. iations. Keywords: biological control; parasitoid; Halyomorpha halys; Ailanthus altissima Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. 1. Introduction This article is an open access article Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a polyphagous invasive stink distributed under the terms and bug from Asia that has been a severe agricultural and nuisance pest in many parts of conditions of the Creative Commons the USA since the late 2000s [1]. A widespread outbreak in 2010 resulted in major losses to Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ the apple and peach crops in the Mid-Atlantic USA [2]. To manage H. halys, many American 4.0/). Insects 2021, 12, 118. https://doi.org/10.3390/insects12020118 https://www.mdpi.com/journal/insects Insects 2021, 12, 118 2 of 12 tree fruit producers increased their use of broad-spectrum insecticides [3], but this is cer- tainly not considered a sustainable, long-term solution. Ultimately, biological control may play an important role in sustainable H. halys management [1]. Surveys of native H. halys parasitoids in North America [4] revealed that the species detected most commonly from sentinel egg masses included members of the genera Anastatus Motschulsky (Hymenoptera: Eupelmidae), Telenomus Haliday (Hymenoptera: Scelionidae), and Trissolcus Ashmead (Hy- menoptera: Scelionidae). However, field studies have suggested that endemic parasitoids and predators in the USA are not yet regulating H. halys populations adequately [4,5]. Detections of North American H. halys parasitoids have been somewhat habitat depen- dent [4]. Trissolcus species tended to be more prevalent in ornamental, semi-natural/urban, and forest habitats than in other systems [4], and Herlihy et al. [6] found that this genus predominated in wooded habitats. Parasitization of sentinel H. halys eggs did not differ between exotic or native host plants but was greatest at the edge of unmanaged woods [7]. Anastatus species were among the most common parasitoids in ornamental systems [8]. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is one of the most impor- tant natural enemies of H. halys in Asia [9,10]. The discovery of an adventive population of T. japonicus in Maryland in 2014 [11] prompted more intensive and extensive surveillance for H. halys parasitoids in North America and Europe, resulting in T. japonicus detections in 13 states, Washington, DC [6,12–14], Canada, Italy, and Switzerland [15–18]. Although Abram et al. [19] noted that the effects of egg parasitoids, including T. japonicus, on H. halys populations have not been quantified, intensified sampling for T. japonicus in the USA to track changes in its spread and abundance is warranted and would benefit from a better understanding of its temporal and spatial distributions. Zhang et al. [10] documented the seasonal parasitism of H. halys eggs by T. japoni- cus in Beijing, China, although its seasonal phenology elsewhere has not been reported. In the USA, it has been detected in woodland [6,20,21] and lightly wooded residential habitats [13], and Herlihy et al. [6] reported that it parasitized significantly more H. halys sentinel eggs in wooded habitats than in soybean or apple plantings. In both the USA [20] and China [10], T. japonicus has also been detected in peach orchards. However, there have not been systematic comparisons of T. japonicus detection frequency and relative abundance among the wooded habitats in which it has been found, particularly those adjacent to crops at risk from H. halys attack. Moreover, although T. japonicus detections in the USA have been most common in arboreal habitats [6,11,21–23], its presence and abundance among different H. halys tree hosts has not been examined. Optimizing the efficiency of sampling to track changes in the range and abundance of T. japonicus in the USA can be achieved and informed by a greater understanding of potential habitat and plant species effects on its detection frequency, and by documenting its seasonal phenology. Here, studies conducted in northern Virginia, USA, where T. japonicus has been present since at least 2015 [21], address adventive T. japonicus captures in relation to habitat type, plant species, and seasonality. 2. Materials and Methods 2.1. Seasonal Phenology and Habitat Type Study sites were unmanaged, wooded habitats adjacent to commercial and experi- mental orchards in the counties of Frederick (14 sites) and Shenandoah (1 site), Virginia, USA, where T. japonicus has been detected consistently since 2015. All sites were within 10 km of Virginia Tech’s Alson H. Smith Jr. Agricultural Research and Extension Center (AHSAREC) (39.112867, −78.284029) in Frederick county, and the same sites were used for trapping in 2018 and 2019. Tree of heaven, Ailanthus altissima (Mill.) Swingle, is an invasive Asian species [24] that often grows prolifically in disturbed or semi-disturbed locations in Virginia and elsewhere in the USA [25]. In this area, it was the most abundant deciduous tree species at the edge of woodlands bordering tree fruit orchards [26] and supports all H. halys life stages [27]. In addition, inspection of the foliage of felled tree of heaven yielded H. halys egg masses Insects 2021, 12, x 3 of 12 Tree of heaven, Ailanthus altissima (Mill.) Swingle, is an invasive Asian species [24] that often grows prolifically in disturbed or semi-disturbed locations in Virginia and else- Insects 2021, 12, 118 3 of 12 where in the USA [25]. In this area, it was the most abundant deciduous tree species at the edge of woodlands bordering tree fruit orchards [26] and supports all H. halys life stages [27]. In addition, inspection of the foliage of felled tree of heaven yielded H. halys egg masses parasitizedparasitized by T. japonicus by T. japonicus [20]. The[20 prevalence]. The prevalence of this tree of thisand treethe occurrence and the occurrence of of both both H. halys andH. halysT. japonicusand T. japonicuson it led toon the it led selection to the selectionof female of tree female of heaven tree of for heaven stand- for standardized ardized sampling.sampling. In this area, threeIn thiscommon area, threehabitat common types in habitat which types tree of in heaven which treegrows of heavenare: 1) spa- grows are: (1) spa- tially isolated, oftentially roughly isolated, circular often roughlypatches typically circular patchesassociated typically with rock associated breaks in with oth- rock breaks in erwise cultivatedotherwise or fallow cultivated fields; 2) orwindbreaks fallow fields; or hedgerows; (2) windbreaks 3) the or edge hedgerows; of woodlands (3) the edge of wood- (Figure 1).