Kamal J. K. Gandhi

Direct and indirect effects of alien insect herbivores on ecological processes and interactions in forests of eastern North America.

Alien invasive insects such as gypsy moth, hemlock woolly adelgid, and emerald ash borer continue to disturb the mixed deciduous and hemlock forests of eastern North America by causing wide-scale defoliation, decline and/or mortality of their hosts. Some of the most devastating species are spreading in “defense free space”, causing extensive mortality of hosts that are inherently susceptible, perhaps due to their lack of coevolutionary history with the invader. These disturbances have altered the dynamics of canopy gaps, coarse woody debris, biogeochemical cycling, and ecological interactions among organisms in terrestrial and aquatic systems, with consequent effects on forest composition, structure, and function. Populations of indigenous species specialized to particular habitats and/or host trees are most likely to decrease, while some generalist and opportunistic species may increase in invaded forests, including exotic plants as their facilitation by alien insects sparks an “invasional meltdown”. Although poorly documented, alien insects may induce positive feedback effects on ecological processes and interactions. For example, effects of herbivory on foliar chemistry may indirectly alter tri-trophic interactions of indigenous herbivores on their shared hosts, slow rates of terrestrial nutrient cycling, and decrease productivity of aquatic habitats based on allochthonous inputs. Tactics used to eradicate or suppress alien insects in forests such as insecticide applications, biological control, and silvicultural prescriptions can also have ecological impacts. As alien insects continue to establish and spread in forests of eastern North America, their already pervasive effects on ecological interactions and ecosystem processes will continue to magnify.

North American arthropods at risk due to widespread Fraxinus mortality caused by the Alien Emerald ash borer

Emerald ash borer (Agrilus planipennis Fairmaire) (EAB), an alien invasive wood-boring buprestid beetle, is causing large-scale decline and mortality of the most widely distributed species of ash (Fraxinus spp.) trees endemic to eastern North America. We determined which arthropod species that are associated with ash may become threatened, endangered, and co-extinct with the demise of ash as a dominant tree species. A literature survey revealed that 43 native arthropod species in six taxonomic groups (Arachnida: Acari; Hexapoda: Coleoptera, Diptera, Hemiptera, Hymenoptera, and Lepidoptera) are known to be associated only with ash trees for either feeding or breeding purposes, and thus face high risk of endangerment. Most of these species are gall-formers followed by folivores, subcortical phloem/xylem feeders, sap feeders, and seed predators. Another 30 arthropod species are associated with 1–2 host plants in addition to ash, and herbivory on these hosts may increase as these arthropods shift from declining ash trees. Extirpation of arthropods dependent upon ash may unleash multiple extinctions of affiliated species with which they may be inextricably linked. The demise of North American ash species due to EAB is expected to lead to biotic loss with cascading ecological impacts and altered processes within forested ecosystems.

Species Dependent Influence of (−)-α-Pinene on Attraction of Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae) to Ethanol-Baited Traps in Nursery Agroecosystems

ABSTRACT Field-based trapping experiments were conducted in Ohio in 2003, 2004, and 2008 to determine the influence of (—)-&agr;-pinene on the attraction of exotic and native ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to ethanol-baited traps. In 2003 and 2004, we determined the effect of adding an (—)-&agr;-pinene ultrahigh release lure (UHR; 2 g/d at 20°C) to traps baited with an ethanol UHR lure (0.39 g/d). Fewer Anisandrus (Xyleborus) sayi (Hopkins) and Xyleborinus saxeseni (Ratzeburg) were collected in 2003 and 2004 from traps baited with ethanol UHR plus (—)-&agr;-pinene UHR compared with ethanol UHR. (—)-&agr;-Pinene also reduced the attraction of Xyloterinus politus (Say) to ethanol-baited traps in 2004. Total captures of Xylosandrus germanus (Blandford) in 2003 were higher in traps baited with ethanol UHR plus (—) -&agr;-pinene UHR than in traps with ethanol UHR alone but not in 2004. In 2008, captures were compared among traps baited with eight combinations of ethanol and (—)-&agr;-pinene at both UHR and low release (LR) rates. Release rates for ethanol LR and (—)-&agr;-pinene LR were 0.027 and 0.0015g/d, respectively. (—)-&agr;-Pinene UHR and (—)-&agr;-pinene LR reduced the attractiveness of ethanol UHR to A. sayi and X. saxeseni. Ethanol UHR was also more attractive than ethanol LR to A. sayi and X. germanus. These findings demonstrate traps baited with ethanol alone are more effective than ethanol plus (—) -&agr;-pinene for monitoring ambrosia beetle flight activity in ornamental nurseries. Ethanol release rate is also an important consideration for monitoring purposes.

Indirect Effects of Emerald Ash Borer-Induced Ash Mortality and Canopy Gap Formation on Epigaeic Beetles

ABSTRACT Exotic herbivorous insects have drastically and irreversibly altered forest structure and composition of North American forests. For example, emerald ash borer (Agrilus planipennis Fairmaire) from Asia has caused wide-scale mortality of ash trees (Fraxinus spp.) in eastern United States and Canada. We studied the effects of forest changes resulting from emerald ash borer invasion on epigaeic or ground beetles (Coleoptera: Carabidae) along a gradient of ash dieback and gap sizes in southeastern Michigan. Ground beetles were sampled in hydric, mesic, and xeric habitats in which black (Fraxinus nigra Marshall), green (Fraxinus pennsylvanica Marshall), and white (Fraxinus americana L.) ash were the most common species, respectively. During 2006–2007, we trapped 2,545 adult ground beetles comprising 52 species. There was a negative correlation between percent ash tree mortality in 2006 and catches of all beetles. Catches of Agonum melanarium Dejean (in 2006) and Pterostichus mutus (Say) (in 2006–2007) were negatively correlated with tree mortality and gap size, respectively. However, catches of Pterostichus corvinus Dejean were positively correlated with gap size in 2006. As ash mortality and average gap size increased from 2006 to 2007, catches of all beetles as well as P. mutus and Pterostichus stygicus (Say) increased (1.3–3.9 times), while species diversity decreased, especially in mesic and xeric stands. Cluster analysis revealed that beetle assemblages in hydric and mesic stand diverged (25 and 40%, respectively) in their composition from 2006 to 2007, and that hydric stands had the most unique beetle assemblages. Overall, epigaeic beetle assemblages were altered in ash stands impacted by emerald ash borer; however, these impacts may dissipate as canopy gaps close.

Species Composition, Seasonal Activity, and Semiochemical Response of Native and Exotic Bark and Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae) in Northeastern Ohio

ABSTRACT In 2007, we surveyed the alien and endemic scolytine (bark and ambrosia beetles) fauna of northeastern Ohio, and for the most abundant species, we characterized their seasonal activity and response to three semiochemical baits. In total ,5,339 scolytine beetles represented by 47 species and 29 genera were caught in Lindgren funnel traps. Three species constituted 57% of the total catch, including Xylosandrus germanus (Blandford), Tomicus piniperda (L.), and Diyocoetes autographus (Ratzeburg). Of the total captured, 32% of the species and ≈60% of the individuals were exotic, suggesting that exotic species numerically dominate the scolytine fauna in some urban areas. More native and exotic species were caught in traps baited with ethanol alone than in traps baited with other lures. However, significantly more individuals, especially of T. piniperda, D. autographus, Gnathotrichus materiarius (Fitch), and Ips grandicollis (Eichhoff), and species were caught in traps baited with ethanol plus &agr;-pinene than in traps baited with ethanol alone or the exotic Ips lure. This suggests that among these baits, the ethanol plus &agr;-pinene baits may be useful in maximizing scolytine beetle catches of these species within this region. Species diversity and richness for both native and exotic beetles was greatest in traps baited with ethanol alone. The period of peak trap capture varied depending upon species: X. germanus was most abundant in traps in mid-May and early-August; T. piniperda in mid-May; D. autographus in early June, mid-July, and mid-September; Anisandrus sayi Hopkins and G. materiarius in mid-May, mid-July, and early September; and I. grandicollis in early April, mid-July, and late September.

Attaching Lures to Multiple-Funnel Traps Targeting Saproxylic Beetles (Coleoptera) in Pine Stands: Inside or Outside Funnels?

ABSTRACT We conducted two field trapping experiments with multiple-funnel traps in 2008 and one experiment in 2010 to determine the effects of lure placement (inside or outside funnels) on catches of saproxylic species of beetles (Coleoptera). The experiments were conducted in southern pine (Pinus spp.) stands in central Georgia using combinations of ethanol, &agr;-pinene, ipsenol, and ipsdienol lures. We report on a modification to the multiple-funnel trap that allows placement of large lures inside the confines of the funnels with minimal blockage. In general, catches of five species of common longhorn beetles (Cerambycidae), two species of regeneration weevils (Curculionidae), four species of bark beetles (Curculionidae: Scolytinae), and seven species of beetle predators and ectoparasites (Cleridae, Histeridae, Tenebrionidae, Trogossitidae, and Zopheridae) were higher in funnel traps with lures attached inside the funnels than in those with lures attached outside of the funnels. Catches of the remaining species were unaffected by lure placement. In no instance were catches of any species lower in funnel traps with lures attached inside the funnels than in those with lures attached outside of the funnels. For most species, catches in modified funnel traps with ethanol, &agr;-pinene, ipsenol, and ipsdienol lures attached inside funnels were comparable with those in cross-vane panel traps.

Impacts of prescribed fire on saproxylic beetles in loblolly pine logs

Abstract.  1. Studies addressing the immediate impacts of fire on forest arthropod communities and their implications for conservation are few, particularly for species within dead wood. To investigate the effects of fire on saproxylic beetles (Coleoptera), we randomly assigned large‐diameter loblolly pine (Pinus taeda L.) logs to a forest scheduled for a prescribed burn (i.e. a low‐intensity surface fire) or to an adjacent unburned forest in Georgia, USA.

Leluthia astigma (Ashmead) (Hymenoptera: Braconidae: Doryctinae) as a Parasitoid of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae: Agrilinae), with an Assessment of Host Associations for Nearctic Species of Leluthia Cameron

Abstract Published host associations are assessed for Leluthia astigma (Ashmead), Leluthia floridensis Marsh, and Leluthia mexicana Cameron, the three known species of Leluthia Cameron in the Nearctic Region. Leluthia astigma is reported as a parasitoid of Agrilus planipennis Fairmaire, emerald ash borer (EAB), infesting Fraxinus americana L., white ash, in Delaware County, Ohio. It is the first species of Leluthia for which a determined species of Agrilus Curtis has been confirmed as a host and the association vouchered. All other hosts reported in the literature for L. astigma require confirmation through rearing from an isolated host or documentation of an unequivocal host-parasitoid association. Leluthia astigma adults reared from parasitoid cocoons collected in Delaware County, Ohio parasitized and produced F1 adults in the laboratory on last-instar EAB larvae collected in Ingham County, Michigan. Parasitism of EAB and other natural history data are reported for L. astigma, including the first records of L. astigma from Kansas and New York.

The Ecology, Behavior, and Biological Control Potential of Hymenopteran Parasitoids of Woodwasps (Hymenoptera: Siricidae) in North America

ABSTRACT Native and exotic siricid wasps (Hymenoptera: Siricidae) can be ecologically and/or economically important woodboring insects in forests worldwide. In particular, Sirex noctilio (F.), a Eurasian species that recently has been introduced to North America, has caused pine tree (Pinus spp.) mortality in its non-native range in the southern hemisphere. Native siricid wasps are known to have a rich complex of hymenopteran parasitoids that may provide some biological control pressure on S. noctilio as it continues to expand its range in North America. We reviewed ecological information about the hymenopteran parasitoids of siricids in North America north of Mexico, including their distribution, life cycle, seasonal phenology, and impacts on native siricid hosts with some potential efficacy as biological control agents for S. noctilio. Literature review indicated that in the hymenopteran families Stephanidae, Ibaliidae, and Ichneumonidae, there are five genera and 26 species and subspecies of native parasitoids documented from 16 native siricids reported from 110 tree host species. Among parasitoids that attack the siricid subfamily Siricinae, Ibalia leucospoides ensiger (Norton), Rhyssa persuasoria (L.), and Megarhyssa nortoni (Cresson) were associated with the greatest number of siricid and tree species. These three species, along with R. lineolata (Kirby), are the most widely distributed Siricinae parasitoid species in the eastern and western forests of North America. Depending upon certain abiotic and biotic factors, we hypothesize that these four parasitoid species may contribute to the biological control of S. noctilio. Major gaps exist regarding parasitoid ecology, including their taxonomy, distribution range, exact siricid and tree hosts, interactions with hosts, phenology, and chemoecology in forest stands. As S. noctilio continues to expand its distribution in North America, a better understanding of the biology of these parasitoids may be needed in coniferdominated landscapes.

A cross‐continental comparison of plant and beetle responses to retention of forest patches during timber harvest

Timber harvest can adversely affect forest biota. Recent research and application suggest that retention of mature forest elements (retention forestry), including unharvested patches (or aggregates) within larger harvested units, can benefit biodiversity compared to clearcutting. However, it is unclear whether these benefits can be generalized among the diverse taxa and biomes in which retention forestry is practiced. Lack of comparability in methods for sampling and analyzing responses to timber harvest and edge creation presents a challenge to synthesis. We used a consistent methodology (similarly spaced plots or traps along transects) to investigate responses of vascular plants and ground-active beetles to aggregated retention at replicate sites in each of four temperate and boreal forest types on three continents: Douglas-fir forests in Washington, USA; aspen forests in Minnesota, USA; spruce forests in Sweden; and wet eucalypt forests in Tasmania, Australia. We assessed (1) differences in local (plot-scale) species richness and composition between mature (intact) and regenerating (previously harvested) forest; (2) the lifeboating function of aggregates (capacity to retain species of unharvested forest); and whether intact forests and aggregates (3) are susceptible to edge effects and (4) influence the adjacent regenerating forest. Intact and harvested forests differed in composition but not richness of plants and beetles. The magnitude of this difference was generally similar among regions, but there was considerable heterogeneity of composition within and among replicate sites. Aggregates within harvest units were effective at lifeboating for both plant and beetle communities. Edge effects were uncommon even within the aggregates. In contrast, effects of forest influence on adjacent harvested areas were common and as strong for aggregates as for larger blocks of intact forest. Our results provide strong support for the widespread application of aggregated retention in boreal and temperate forests. The consistency of pattern in four very different regions of the world suggests that, for forest plants and beetles, responses to aggregated retention are likely to apply more widely. Our results suggest that through strategic placement of aggregates, it is possible to maintain the natural heterogeneity and biodiversity of mature forests managed for multiple objectives.