Arthropod Community in Hybrid Hazelnut Plantings in the Midwestern United States.

There is a lack of knowledge of the arthropod communities in both wild hazelnut and cultivated hybrid hazelnut ecosystems in the Midwestern United States. Our goal was to characterize the composition of these arthropod communities in hazelnut plantings. We surveyed six experimental plantings of hazelnuts in Wisconsin and two in Minnesota during growing seasons, from May 2017 to August 2021. We used four methods to survey the arthropod community of these plantings: ad libitum survey of specimen observations and collection, dissection of hazelnut buds and nuts, cone traps placed on the ground, and beat sheet sampling of plants. We registered 116 different morphospecies of five classes and 83 families. Arthropods with known feeding habits were grouped into four guilds: 59 herbivores, 36 carnivores (predators, parasites, and parasitoids), 4 decomposers (detritivores and scavengers), and 4 omnivores. While we registered 12 herbivorous species that could potentially cause damage to hazelnuts, we directly observed nine of them feeding upon or damaging plant parts: Phytoptus avellanae s.l. Nalepa (Eriophyoidea: Phytoptidae), Curculio obtusus Blanchard and Strophosoma melanogrammum Förster (Coleoptera: Curculionidae), Popillia japonica Newman (Coleoptera: Scarabeidae), Parthenolecanium sp. (Hemiptera: Coccidae), Euschistus servus euschistoides Say (Hemiptera: Pentatomidae), aphids (Hemiptera: Aphididae), Acleris sp., and Choristoneura rosaceana Harris (Lepidoptera: Tortricidae). We also registered eight species of parasites or parasitoids that could offer biocontrol services in the cropping system. These findings provide a foundation for future targeted studies on potential pests and beneficial arthropods, as well as ecological interactions within the hybrid hazelnut ecosystem in the Midwest.

Hazel plants (Corylus avellana Linnaeus) (Fagales: Betulaceae) are trees whose nuts have been prehistorically a source of food for humans (Holst 2010). They have been cultivated in Eurasia for hundreds of years. In the United States, the European hazelnut is mainly cultivated in the Pacific Northwestern (PNW) states of Oregon and Washington. About 99% of the hazelnut crop in the United States is produced in Oregon, setting this country in fourth place with about 5% of the world crop (Mehlenbacher and Olsen 1997, Oregon Department of Agriculture 2021). In the Midwestern region of the United States, the climatic conditions and presence of disease, like the Eastern Filbert Blight, are not suitable for C. avellana to thrive or produce nuts (Gold 2016, Taghavi et al. 2018). However, there are two native Corylus species to this region, the American hazelnut (Corylus americana Marshall) and the beaked hazelnut (Corylus cornuta Marshall). In the Eastern and Midwest states, there is a growing initiative to develop hybrid hazelnuts (C. avellana × C. americana or C. avellana × C. cornuta) that combine the disease resistance and cold hardiness of the native species with yield and processing characteristics of nuts of C. avellana for production in these regions. The global demand for hazelnuts is rising, both for fresh eating and for oil because the nuts are high in vitamins and oil content (Molnar et al. 2005, Braun and Jensen 2015, Braun et al. 2019).

Like in other cropping systems, there is a diverse suite of arthropods associated with Corylus spp. Descriptions of arthropod communities associated with hazelnut ecosystems, including harmful pests, are mostly from plantings of European hazelnuts in the Eastern Hemisphere (Villaronga and García-Mari 1988, Tavella et al. 1997, Snare 2006) and the PNW region in the United States (AliNiazee 1980, 1998; Brenner 1986; Walton et al. 2007, 2009; Wiman and Bell 2021). According to AliNiazee (1998), there are 280 species of insects and mites associated with hazelnuts plantings in Turkey, with approximately 150 species feeding on hazelnut plants, but only 47 species cause most of the damage. In the United States, AliNiazee (1998) identified about 150 species of insects and mites in hazelnut ecosystems in the PNW, with approximately half of those species being beneficial. AliNiazee (1980), Snare (2006), Walton et al. (2007, 2009), and Wiman and Bell (2021) mention 27 species of arthropods that cause damage to hazelnut cultivars in Oregon and Washington spanning both specialist and generalist feeding habits.

Arthropods associated with hazelnut plantings have never been surveyed in the Eastern or Midwest regions of the United States. Little is known about arthropod communities associated with native beaked hazelnut or American hazelnut other than the hazelnut weevil (Curculio obtusus Blanchard) (Coleoptera: Curculionidae) (Treadwell 1996). Our goal was to characterize the composition of arthropod communities present in hazelnut experimental plantings in the Upper Midwestern United States. Knowledge of potential arthropod pests and beneficial natural enemies is a crucial first step in ecological research needed to create pest management recommendations, should they become required.

Methods

We surveyed arthropods in eight hybrid hazelnut research plantings throughout the Upper Midwestern United States, six in Wisconsin: Bayfield, Ashland, Hayward, Spooner, Tomahawk, and Stoughton; and two in Minnesota: Rosemount and Saint Paul (Table 1). In each of these locations, there are trials of hybrid hazelnut genotypes. Plantings’ ages varied from 12 yr to a few months; the latter where new plants were installed within the primary plantings. The weed control methods used varied among plantings (Table 1). No insecticide was used in any plantings.

Table 1.

Location and characteristics of each experimental hybrid and American hazelnut planting in the Upper Midwest of the United States

Planting	State	Coordinates	Size (ha)	Year planted	Weed control
Ashland	Wisconsin	46°35ʹ04ʹʹN 90°57ʹ56ʹʹW	0.19	2012	Herbicide in early spring, weed-whipping and hand weeding as needed, and one mowing in late summer.
Bayfield	Wisconsin	46°50ʹ19ʹʹN 90°50ʹ02ʹʹW	1.53	2009	Herbicide in early spring, weed-whipping and hand weeding as needed, and one mowing in late summer.
Hayward	Wisconsin	45°59ʹ47ʹʹN 91°30ʹ26ʹʹW	0.83	2014	Herbicide in early spring, weed-whipping and hand weeding as needed, and mowing two or three times per season.
Spooner	Wisconsin	45°49ʹ22ʹʹN 91°52ʹ05ʹʹW	0.36	2011	Herbicide in early spring, weed-whipping and hand weeding as needed, and mowing two or three times per season.
Stoughton	Wisconsin	42°56ʹ37ʹʹN 89°09ʹ41ʹʹW	0.35	2011	Mowing once or twice per season.
Tomahawk	Wisconsin	45°30ʹ23ʹʹN 89°32ʹ59ʹʹW	0.21	2012	Weed whipping once in late summer.
Rosemount	Minnesota	44°43ʹ36ʹʹN 93°05ʹ59ʹʹW	0.18	2011-2013	Weed whipping and mowing as needed
Saint Paul	Minnesota	44°59ʹ53ʹʹN 93°10ʹ30ʹʹW	0.68	2009	Weed whipping and mowing as needed

We used four methods of arthropod sampling (with some variability across sites, described below): 1) ad libitum survey by specimen collection and visual observations while working in the field throughout each growing season at all locations (both on hazelnut plants and other vegetation within the plantings); 2) collection and dissection of hazelnut buds and nuts, both during the growing period and after harvest, at all locations; 3) four metal mesh cone weevil traps placed on the ground, each one under a different hazelnut plant in Bayfield only in 2019 and 2020, checked weekly with all arthropod specimens collected (Treadwell 1996 and Mulder et al. 2012); 4) beat sheet sampling done weekly from May to July of 2020 and 2021 in both Minnesota locations via beating 12 random hazel plants with a stick 10 times over a one square meter white canvas. Across all methods, the Bayfield planting was the most visited and intensely sampled planting in Wisconsin.

For Wisconsin locations, arthropods were collected or observed for 5 yr, from May to October 2017 to 2020, and May to July in 2021. Specimens were collected into sealable plastic bags or 7 ml plastic vials and stored in a refrigerator at ~4°C or in 70% isopropyl alcohol. Specimens representing new records for the state of Wisconsin were deposited in the Wisconsin Insect Research Collection. Specimens were identified to species level when possible. Some specimens, such as larvae, were identified to family or genus level based on the availability of taxonomic keys for those groups (MacKay 1962; McAlpine 1981, 1987; Vickery and Kevan 1986; Stehr 1987, 1991; Anderson and Howden 1994; Arnett and Thomas 2001, 2002; Wagner et al. 2001; Johnson and Triplehorn 2004; Wagner 2005; Packer et al. 2007; Bright and Bouchard 2008; Paiero et al. 2013; Hoebeke and Sprichier 2016; Whitehead et al. 2018).

For Minnesota locations, arthropods were observed or collected from April to August of 2020 and 2021. All weevils were collected into sealable plastic bags and frozen until they could be identified to species. Buprestid specimens were identified to genus by Patrick Perish (University of Minnesota). All other arthropods were identified by HNS and confirmed by uploading photographs to iNaturalist (www.inaturalist.org).

We organized all species or morphospecies into four guilds according to their feeding habits: carnivores (natural enemies such as predators, parasites and parasitoids), decomposers (detritivores and scavengers), herbivores, and omnivores. In the cases where the juveniles are carnivorous, but the adults are herbivorous, we placed the arthropod into the carnivore guild. When we could not identify the species, or the taxa has a wide spectrum of feeding habits, we elected not to assign a guild. We did not include ticks, some spiders, adult Lepidoptera, or common species of Diptera unless of natural enemy importance, such as syrphid flies.

Results

We recorded 116 morphospecies of 83 families, 18 orders, and five classes. One superfamily (Chalcidoidea; Hymenoptera), was included in our tally, as well as two of Odonata and Trichoptera that were not identified to family level. Of the 116 morphospecies, only 75 of them were identified to species or genera (Table 2). For the four guilds, we recorded 59 morphospecies of arthropods that are considered herbivores, 36 carnivores, 4 omnivores, and 4 decomposers.

Table 2.

Arthropods observed and collected in hybrid hazelnut experimental plantings in six Wisconsin locations (A=Ashland, B=Bayfield, H=Hayward, S=Spooner, St=Stoughton, T=Tomahawk), and two in Minnesota (R=Rosemount, and SP=Saint Paul). Feeding habits (D=detritivore, H=herbivore, Pr=predator, Ps=parasite or parasitoid, O=omnivore, S=scavenger) separated by commas include habit of different spp. within the group, separated by hyphen are habit of immature vs adult individual within the species

Class	Order	Family	Scientific name	Common name	Feeding habits	Location	Life Stage
Arachnida	Eriophyoidea	Phytoptidae	Phytoptus avellanae s.l. (Nalepa)	Filbert bud mite	H	A, B, H, S,T, R, SP	Immature and adult
	Mesostigmata	Phytoseiidae			Pr	B	Adult
	Aranae	Araneidae	Araneus trifolium (Hentz)	Shamrock orbweaver	Pr	B, S	Adult
			Argiope sp.		Pr	St	Adult
			Argiope aurantia (Lucas)	Yellow garden spider	Pr	SP	Adult
			Argiope trifasciata (Forsskål)	Whitebacked garden spider	Pr	S	Adult
		Philodromidae	Thanatus sp.		Pr	B	Adult
		Salticidae	Dendryphantina sp.		Pr	R, SP
			Phidippus sp.	Bold jumper spider	Pr	S	Adult
		Thomisidae	Mecaphesa sp.	Crab spiders	Pr	R	Immature and adult
Collembola	Entomobryomorpha	Entomobryidae		Spring tail	D, Pr	B	Adult
Diplopoda	Polyxenida	Polyxenidae		Bristle millipedes	D, Pr	B	Adult
Insecta	Coleoptera	Buprestidae	Agrilus spp.	Jewel beetles	H	R, SP	Adult
		Carabidae	Harpalus sp.	Ground beetle	O	B	Adult
		Chrysomelidae	Anomoea laticlavia (Förster)	Claycolored leaf beetle	H	T	Adult
			Diachus auratus (Fabricius)	Bronze leaf beetle	H	B	Adult
			Pachybrachis sp.	Scriptured leaf beetle	H	B	Adult
			Tricholochmaea sp.	Leaf beetle	H	B	Adult
		Coccinellidae	Brachiacantha ursina (Fabricius)	Ursine spur leg lady beetle	Pr	SP	Adult
			Coccinella septemounctata (Linnaeus)	Sevenspotted lady beetle	Pr	B	Adult
			Hyperaspis sp.	Sigil lady beetle	Pr	B	Adult
		Curculionidae	Barypeithes pellucidus (Boheman)	Hairy spider weevil	H	B	Adult
			Calomycertus setarius (Roelofs)	Imported long-horned weevil	H	R	Adult
			Curculio obtusus (Blanchard)	Hazelnut weevil	H	B, H, T, R, S, SP	Immature and adult
			Larinus carlinae (Schoenherr)	Canada thistle bud weevil	H	R	Adult
			Larinus obtusus (Gyllenhal)	Knapweed seedhead weevil	H	B, H	Adult
			Lixus concavus (Say)	Rhubarb weevil	H	R	Adult
			Otiorhynchus ovatus (Linnaeus)	Strawberry root weevil	H	B	Adult
			Phyllobius oblongus (Linnaeus)	European snout weevil or brown leaf weevil	H	B	Adult
			Polydrusus formosus (Mayer)	Green immigrant leaf weevil	H	B, H, R, SP, T	Adult
			Polydrusus impressifrons (Gyllenhal)	Pale green weevil or leaf weevil	H	R, SP	Adult
			Romualdius scaber (Linnaeus)	Crusted root weevil	H	B	Adult
			Strophosoma melanogrammum (Förster)	Nut leaf weevil	H	B	Adult
			Tychius sp.	Alfalfa weevil	H	B	Adult
		Elateridae	Aeolus sp.	Click beetle	H	B	Adult
			Melanotus spp.	Click beetle	H	B	Adult
		Lampyridae		Firefly	Pr	B	Adult
			Photinus sp.	Firefly	Pr	R, St	Adult
		Latridiidae	Corticarina sp.	Minute brown scavenger beetle	S	B	Adult
		Lycidae	Calopetron reticulatum (Fabricius)	Banded net-wing beetle	Pr-H	B	Adult
		Mycetophagidae	Typhaea stercorea (Linnaeus)	Hairy fungus beetle		B	Adult
		Phalacridae		Shining flower beetle	H	B	Adult
		Ptinidae		Ptinid or Anobiid beetle	H, O, S	B	Adult
		Scarabeidae	Popillia japonica (Newman)	Japanese beetle	H	R, SP, St	Adult
		Tenebrionidae	Isomira sp.	Comb-clawed beetle	S	B	Adult
	Dermaptera	Forficulidae	Forficula auricularia (Linnaeus)	European earwig	O	B, S	Adult
	Diptera	Anthomyiidae		Root maggot fly	H, Pr, Ps	B	Adult
		Asilidae	Promachus sp.	Robber fly	Pr	B	Adult
		Chloropidae		Frit fly	H, Pr, Ps, S	B	Adult
		Dolichopodidae		Longlegged fly	H, Pr	B	Adult
		Drosophilidae		Vinegar fly		B	Adult
		Fanniidae			S	B	Adult
		Hybotidae	Platypalpus sp.	Hybotid dance fly	Pr	B	Adult
		Phoridae		Scuttle fly	H, Pr, Ps, S	B	Adult
		Polleniidae	Pollenia sp.	Cluster fly	H, Pr, Ps	B	Adult
		Psilidae		Rust fly	H	B	Adult
		Sciaridae		Dark wing fungus gnat	D	B	Adult
		Syrphidae	Eupeodes sp.	Hover fly	Pr-H	B	Adult
		Tachinidae			Ps-H	S	Larvae found in slug moth caterpillar
		Therevidae		Stiletto fly	Pr-H	B	Adult
		Tipulidae		Crane fly	O	B	Adult
	Hemiptera	Alydidae	Alydus sp.	Broad headed bug	H, S	B, S	Adult
		Aphidae		Aphids	H	B	Immature and adult
		Caliscelidae		Piglet bug	H	B	Adult
		Cercopidae		Spittle bug	H	B	Immature and adult
		Cicadellidae		Leafhopper	H	B	Adult
		Coccidae	Parthenolecanium sp.	Lecanium scales	H	B, H, S	All stages
		Dictyopharidae		Planthopper	H	B	Adult
		Lygaeidae		Milkweed bug	H	B	Immature
		Pentatomidae	Euschistus servus euschistoides (Say)	Brown stink bug	H	B, S, A, SP	Immature and adult
			Euschistus tristigmus (Say)	Dusky stink bug	H	SP
			Podisus maculiventris (Say)	Spined soldier bug	H	SP	Adult
		Reduviidae (Latreille)		Assassin bugs	Pr	B	Egg mass
		Rhyparochromidae	Slaterobius insignis (Uhler)	Dirt-colored seed bug	H	B	Adult
	Hymenoptera	Andrenidae		Mining bees	H	B	Adult
		Apidae		Apid bees	H	B, S	Adult
		Braconidae		Parasitoid wasp	Ps	B	Adult and mass of cocoons
			Aleiodes sp.	Mummy-wasp	Ps	H, S	Parasitoid in a caterpillar
		Superfam: Chalcidoidea			Ps	B	Adult
		Crabronidae (Latreille)		Crabronid wasp	Pr	B	Adult
		Eupelmidae		Chalcid wasp	Ps	B	Adult
		Formicidae	Formica sp.	Field ants	Pr	B, S	Adult
			Tetramorium immigrans (Santschi)	Pavement ant	O	B	Adult
		Halictidae	Sphecodes sp.	Cuckoo bee	Ps-H	B	Adult
			Lasioglossum sp.	Sweat bee	H	B	Adult
		Ichneumonidae			Ps	B	Adult
		Megachilidae	Osmia sp.	Mason bee	H	B	Adult
		Pompilidae (Latreille)		Spider wasp	Ps-Pr	B	Adult
		Tenthredinidae	Craesus sp.	Sawfly	H	R, S	Immature
		Sphecidae		Threaded-waist wasp	Ps-H	B	Adult
		Vespidae	Polistes sp.	Paper wasp	Pr-H	S	Nest and adult
	Lepidoptera	Coleophoridae		Casebearer	H	B	Cocoon
		Erebidae	Halysidota tessellaris (J. E. Smith)	Pale or banded tussock moth	H	B, S, SP	Immature
			Lymantria dispar (Linnaeus)	Gypsy moth	H	B	Immature
		Geometridae	Erannis tiliaria (Harris)	Linden looper caterpillar	H	S	Immature
		Lasiocampidae	Malacosoma americanum (Fabricius)	Eastern tent caterpillar	H	T	Immature
			Malacosoma disstria (Hübner)	Forest tent caterpillar	H	B, S	Immature
		Limacodidae	Lithacodes sp.	Yellow-shouldered slug moth	H	S	Immature
		Noctuidae		Looper moth	H	B	Immature
		Notodontidae	Schizura unicornis (J.E.Smith)	Unicorn caterpillar	H	S	Immature
		Nymphalidae	Danaus plexippus (Linnaeus)	Monarch	H	B, H	Adult
		Psychidae	Psyche casta (Pallas)	Bagworm	H	B	Adult and cocoons
		Saturniidae	Antheraea polyphemus (Cramer)	Polyphemus moth	H	B, R, S, SP	Immature, cocoon, and adult
			Hyalophora cecropia (Linnaeus)	Cecropia moth or giant silk moth	H	H, S	Immature
		Sphingidae	Poanias excaecata (J.E.Smith)	Blind sphinx moth	H	B, H, S	Immature
		Tortricidae	Acleris sp.	Leafroller	H	B	Immature
			Choristoneura rosaceana (Harris)	Oblique banded leafroller	H	B	Immature and adult
	Neuroptera	Chysopidae		Green lacewing	Pr	B	Adult
		Mantispidae	Climaciella brunnea (Say)	Brown mantid fly	Pr	R	Adult
	Odonata			Dragonflies	Pr	A, B, H, S	Adult
	Orthoptera	Acrididae	Melanoplus bivittatus (Say)	Two-striped grasshopper	H	A, B, S	Immature and adult
				Slanted faced grasshopper	H	B	Immature
	Phasmatodea	Diapheromeridae	Diapheromera femorata (Say)	Northern walkingstick	H	S	Adult
	Thysanoptera	Phlaeothripidae		Tube tailed thrips	Pr	B	Adult. In hazelnut bud infested with filbert bud mites
	Trichoptera			Caddisfly		B	Adult
Malacostraca	Isopoda	Oniscidae		Sowbugs	D	B	Adult

Eight species of herbivores, C. obtusus, Phytoptus avellanae s.l. Nalepa (Eriophyoidea: Phytoptidae), Agrilus spp. (Coleoptera: Buprestidae), Strophosoma melanogrammum Förster (Coleoptera: Curculionidae), Popillia japonica Newman (Coleptera: Scarabeidae), Euschistus servus Say (Hemiptera: Pentatomidae), Parthenolecanium sp. (Hemiptera: Coccidae), and aphids (Hemiptera: Aphidiade) were observed feeding on various parts of the hazelnut plants. Acleris sp. (Lepidoptera: Tortricidae) and Choristoneura rosaceana Harris (Lepidoptera: Tortricidae) larvae were collected from rolled hazel leaves on the plant. Larvae of two species of tent caterpillars (Malacosoma disstria Hübner and M. americanum Fabricius) (Lepidoptera: Lasiocampidae) and sawfly larvae (Craesus sp.) (Lepidoptera: Tenthredinidae) were observed on hazelnut leaves with signs of herbivory; however, we did not directly see these larvae feeding on the plants. In 2017, we collected the first record of S. melanogrammum for Wisconsin.

Among the carnivores, we identified eight species of spiders, and eight parasites and parasitoids. We found two natural enemies inside galls formed by P. avellanae: a predatory mite (Mesostigmata: Phytoseiidae) and a tube tailed thrips (Thysanoptera: Phlaeothripidae). We also found a tachinid fly larva (Diptera: Tachinidae) inside a slug moth caterpillar (Lithacodes sp.) (Lepidoptera: Limacodidae) and a mummy wasp, Aleiodes sp. (Braconidae: Hymenoptera), parasitizing an unidentified caterpillar.

Discussion

Hazelnut planting ecosystems in the Midwestern United States have a richness of species close to that described by AliNiazee (1998) for the PNW, with about half of the species known as, or with the potential, to be beneficial arthropod species. Of the two species of filbert bud mites (Eriophyoidea) reported causing bud galls in hazelnuts, only P. avellanae was present in our eight plantings. This mite is an exotic species, that arrived in the United States most likely from the introduction of European hazelnut cultivars (Ourecky and Slate 1969). Other pest arthropods reported by AliNiazee (1980, 1998), Treadwell (1996), Snare (2006), Walton et al. (2007), and Wiman and Bell (2021) present in our hazelnut plantings are C. rosaceana, Parthenolecanium sp. scales, M. disstria and C. obtusus. This latter mentioned species is the only one found inside the hazelnut shell feeding on the kernel. Except for P avellanae and C. obtusus, none of the other herbivorous species or morphospecies observed were seen in quantities that sparked concern of economically damaging levels. The Japanese beetle (P. japonica), present in Minnesota and Wisconsin, was abundant, although it is not known to what extent it may cause damage of economic consequence to hazelnut.

Strophosoma melanogrammum and Otiorhynchus ovatus Linnaeus (Coleoptera: Curculionidae) are two introduced and invasive species from Europe observed and collected in abundance in Bayfield. Based on reports from Alford (2014), Nielsen et al. (2004), and Urban (1999), S. melanogrammum is considered a pest on oaks, hazels, and greenery plantations in Europe as it feeds on hazelnut vegetative and floral buds, among other vegetative parts. Strophosoma melanogrammum is a parthenogenetic species that may have the potential to become a pest to hazelnut plantings in the Midwestern region. This species was only recorded in Bayfield. We do not know how or when it arrived at the area.

Natural enemies found in Oregon hazelnut orchards that we also observed in our plantings included one species of Chrysopidae, Forficula auricularia Linnaeus (Dermaptera: Forficulidae), ladybird beetles (Coleoptera: Coccinellidae), and syrphid flies (Diptera: Syrphidae) (Walton et al. 2009). We also noted several species of ground beetles (Coleoptera: Carabidae) and spiders. Collectively, none of these natural enemies likely have large impacts on hazelnut pests such as C. obtusus. The two predatory morphospecies we detected inside the galls formed by P. avellanae, a predatory mite and a tube tailed thrips, may be natural enemies of the harmful filbert bud mites and warrant future studies. Other important beneficial morphospecies recorded were tachinid flies and two families of parasitoid wasps, Braconidae and Ichneumonidae, that were quite abundant. Some species found were beneficial for reasons other than biological control of hazelnut pests, such as Larinus obtusus Gyllenhal (Coleoptera: Curculionidae). The latter insect aids in the control of the spotted knapweed (Centaurea stoebe Linnaeus) (Asterales: Asteraceae) (Panke et al. 2012, WSU 2021), which is an introduced aggressive invasive plant species. Many other species found that were either assigned a decomposer guild or not assigned a guild could provide other essential services to the hazelnut ecosystem such as carbon cycling and serving as alternative food sources for natural enemies.

This base line list of species or morphospecies present in hybrid hazelnut plantings in the Upper Midwest provides a foundation for future research on possible pests, beneficial arthropods, and ecological interactions which are needed to understand the complexity of these ecosystems, and to develop pest management plans for this novel crop.