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A predator, Laricobius osakensis Montgomery and Shiyake (Coleoptera: Derodontidae), is being mass-produced and released for the biological control of the invasive hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). To better understand and predict the seasonality of this predator in North America, the development and reproduction of L. osakensis were evaluated at constant temperatures ranging from 5 to 22°C. The predicted seasonal biology was compared with data from field collections. L. osakensis did not complete development from egg to adult at the two lowest temperatures tested, 5 and 8°C, but did so at the highest temperature of 22°C. The minimum development thresholds were estimated for eggs (4.2°C), first (1.8°C), second (5.5°C), third (4.6°C), and fourth instar (4.1°C), prepupa (3.6°C), and pupa (7.5°C). Oviposition rates were significantly greater at 5 and 10°C than at 20 and 25°C. Head capsule width significantly increased for each of the four larval instars with a mean of 0.19, 0.26, 0.35, and 0.44 mm, respectively. Laboratory and field data were used to develop a phenology forecasting model to predict the occurrence of all developmental stages of L. osakensis. This model will allow land managers to more accurately predict the optimal timing for L. osakensis larval sampling throughout its established range.

Laurel wilt is a destructive vascular disease of trees in the laurel family (Lauraceae) caused by a nonnative insect/pathogen complex. This study monitored the recent spread and impact of laurel wilt in sassafras (Sassafras albidum [Nutt.] Nees) from the Gulf-Atlantic Coastal Plain region of the southeastern United States (US) into the adjacent Piedmont/Sandhills and Mountain regions. Laurel wilt was detected at thirteen of forty-six sassafras sites including seven outside the Coastal Plain. Compared to nondiseased sites, sassafras mortality due to laurel wilt increased rapidly from 2018 to 2020 and occurred in all diameter classes monitored (≥ 5 cm diameter at breast height, dbh). Flight trapping for the laurel wilt vector, the redbay ambrosia beetle (RAB, Xyleborus glabratus Eichhoff), with α-copaene lures did not enhance early detection of latent laurel wilt infections. Seasonal flight activity of the RAB in the Piedmont and Mountains suggested two generations per year with little to no flight from December through March. Study Implications Sassafras is the most widely-distributed lauraceous tree species in the US and is valued for its ecological functions, durable wood, and numerous cultural uses. Our results strongly suggest the potential for substantial loss of the existing sassafras resource as laurel wilt continues spreading through the eastern US. Survey traps baited with current lures for the primary insect vector are unlikely to improve early detection of new laurel wilt infections. The georeferenced network of plots established for this project provides baseline data for future monitoring efforts and could be revisited to look for evidence of sassafras resistance to the laurel wilt pathogen.

Following the adventive arrival, subsequent spread, and ensuing impact of Adelges tsugae Annand (Hemiptera: Adelgidae), the hemlock woolly adelgid (HWA) in the eastern United States, a robust initiative was launched with the goal of decreasing ecosystem impacts from the loss of eastern hemlock (Pinales: Pinaceae). This initiative includes the use of biological control agents, including Laricobius spp. (Insecta: Coleoptera). Laboratory production of these agents is limited by subterranean mortality and early emergence. Therefore, the subterranean survivorship and timing of emergence of a mixture of Laricobius spp. was investigated. PVC traps internally lined with a sticky card and covered with a mesh screen were inserted into the soil to measure the percent emergence of adults based on the number of larvae placed within. The number of emerged adults in the field and laboratory-reared larval treatments was adjusted based on emergence numbers in the control and used as the response variable. Independent variables included in the final model were: treatment (field-collected vs. laboratory-reared), organic layer depth (cm), soil pH, and April-to-December mean soil moisture. No differences were found in survivorship between field-collected and laboratory-reared treatments. As pH and organic layer increased survivorship decreased, significantly. Although the majority of emergence occurred in the fall, emergence also occurred in spring and summer. The occurrence of spring and summer emergence and low survivorship (17.1 +/- 0.4%) in the field across all treatments suggests that these are characteristics of Laricobius spp. field biology in their introduced range and not artifacts of the laboratory rearing process. United States Department of Agriculture Forest ServiceUnited States Department of Agriculture (USDA)United States Forest Service [15-CA-11420004-0260] Published version We thank E. Lane, A. Hillen, R. Anderson, C. Jubb, and C. Preston for their technical assistance in the field and in the laboratory, and the University of Virginia's Mountain Lake Biological Station for allowing us to use their site. We would also like to thank the United States Department of Agriculture Forest Service for funding this work (15-CA-11420004-0260). Public domain – authored by a U.S. government employee

Phytosanitary treatments for logs and barked wood products are needed to mitigate the spread of thousand cankers disease through the movement of these commodities. The disease threatens eastern black walnut (Juglans nigra L.) populations in the United States. It is caused by repeated attacks by the walnut twig beetle (Pityophthorus juglandis Blackman) and subsequent canker development caused by the fungal pathogen Geosmithia morbida M. Kolařík et al. Methyl bromide (MB) fumigations were evaluated for efficacy against P. juglandis and G. morbida in J. nigra bolts. Fumigation with 82 mg/L MB for 24 h at 4.5° C eliminated P. juglandis in J. nigra, but was ineffective against G. morbida. Subsequent experiments focused on eliminating G. morbida, but results were inconclusive because of low rates of pathogen recovery from naturally infested control bolts. Final experiments used J. nigra bolts artificially inoculated with G. morbida. Fumigations with 240 and 320 mg/L MB for 72 h at 10° C were effective in eliminating G. morbida from J. nigra bolts. Results confirm that the USDA fumigation treatment schedule for logs with the oak wilt pathogen will also mitigate the risk of spreading the thousand cankers disease vector and pathogen by movement of walnut bolts and wood products.

The walnut twig beetle (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae) is a regulated pest in the United States due to its causal role in thousand cankers disease of walnut trees, including the commercially valuable eastern black walnut (Juglans nigra L.). Several state quarantines designed to limit spread of P. juglandis regulate movement of kiln-dried walnut lumber that contains bark. Previous research demonstrated that P. juglandis will enter and re-emerge from bark of kiln-dried, J. nigra slabs subjected to extreme beetle pressure (baited with a pheromone lure and hung in infested J. nigra trees). This study evaluated P. juglandis bark colonization of both kiln-dried and fresh J. nigra slabs, varying the presence of aggregation pheromone and relative proximity to a beetle source. Wood treatment, slab location, and pheromone presence all significantly affected P. juglandis colonization, as assessed by subsequent beetle emergence. When placed on the ground directly beneath infested trees, kiln-dried slabs were not colonized, and fresh slabs were colonized only when baited with the pheromone lure (6/14 replicates). When placed in crowns of infested trees, kiln-dried slabs were colonized only when baited with pheromone (3/14 replicates), whereas fresh slabs were colonized with and without pheromone (14/14 and 1/13 replicates, respectively). Timing of emergence indicated that beetles did not reproduce in kiln-dried bark. Results suggest that the risk of kiln-dried walnut bark becoming colonized by the P. juglandis during movement of commercial wood products is very low. This information may be useful to government agencies that administer quarantines regulating the transport of walnut lumber.

Several North American walnut species (Juglans spp.) are threatened by thousand cankers disease which is caused by the walnut twig beetle (Pityophthorus juglandis Blackman) and its associated fungal plant pathogen, Geosmithia morbida M. Kolarík, E. Freeland, C. Utley and N. Tisserat sp. nov. Spread of this disease may occur via movement of infested black walnut (Juglans nigra L.) wood. This study evaluated the ability of P. juglandis to colonize J. nigra wood previously treated with various phytosanitation methods. Steam-heated and methyl bromide-fumigated J. nigra logs, as well as kiln-dried natural wane J. nigra lumber (with and without bark) were subsequently exposed to P. juglandis colonization pressure in two exposure scenarios. Following a pheromone-mediated, high-pressure scenario in the canopy of infested trees, beetles readily colonized the bark of steam-heated and methyl bromide-fumigated logs, and were also recovered from kiln-dried lumber on which a thin strip of bark was retained. In the simulated lumberyard exposure experiment, during which samples were exposed to lower P. juglandis populations, beetles were again recovered from bark-on steam-heated logs, but were not recovered from kiln-dried bark-on lumber. These data suggest logs and bark-on lumber treated with phytosanitation methods should not be subsequently exposed to P. juglandis populations. Further beetle exclusion efforts for phytosanitized, bark-on walnut wood products transported out of quarantined areas may be necessary to ensure that these products do not serve as a pathway for the spread of P. juglandis and thousand cankers disease.

Thousand cankers disease, caused by the invasive bark beetle Pityophthorus juglandis Blackman and an associated fungal pathogen Geosmithia morbida M.Kolařík, E. Freeland, C. Utley, N. Tisserat, currently threatens the health of eastern black walnut (Juglans nigra L.) in North America. Both the beetle and pathogen have expanded beyond their native range via transport of infested walnut wood. Geosmithia morbida can develop in seedlings following inoculation, but the ability of P. juglandis to colonize young, small diameter trees has not been investigated. This study assessed the beetle's colonization behavior on J. nigra nursery trees. Beetles were caged directly onto the stems of walnut seedlings from five nursery sources representing a range of basal stem diameter classes. Seedlings were also exposed to P. juglandis in a limited choice, field-based experiment comparing pheromone-baited and unbaited stems. When beetles were caged directly onto stems, they probed and attempted to colonize seedlings across the range of diameters and across sources tested, including stems as small as 0.5 cm in diameter. In the field experiment, beetles only attempted to colonize seedlings that were baited with a pheromone lure and appeared to prefer (though not statistically significant) the larger diameter trees. Despite several successful penetrations into the phloem, there was no evidence of successful progeny development within the young trees in either experiment. Further investigation is recommended to better elucidate the risk nursery stock poses as a pathway for thousand cankers disease causal organisms.

The hemlock woolly adelgid Adelges tsugae Annand (Hemiptera: Adelgidae), is a non-native invasive pest that has caused widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr. (Pinales: Pinaceae)) and Carolina hemlock (T. caroliniana Engelm.) in the eastern United States. Our preliminary experiments evaluated the utility of a rain-down technique to induce artificial infestations of A. tsugae on hemlock seedlings en masse. Experiments were conducted in PVC (1 m3) cages topped with poultry wire for placement of A. tsugae-infested branches, and with 1 m2 gridded glue sheets and/or hemlock seedlings placed below to capture adelgid abundance, distribution, and infestation rate data. In the March 2011 experiment, the density of progrediens crawlers (adelgid nymphs, first instars) that rained down inside the PVC cages was significantly higher in the high ovisac treatment compared to the low ovisac treatment, with an estimated 513,000 and 289,000 crawlers per m2 falling beneath each treatment, respectively. Resulting A. tsugae infestation rates on Carolina hemlock seedlings placed inside the cages did not differ between the treatments but were at or above established damage threshold densities for the adelgid. Infestation rates on eastern hemlock seedlings that were placed in cages nine days after the experiment started were below damage threshold levels and did not differ between the treatments. In the May 2011 experiment, the density of sistens crawlers raining down was substantially lower, with 17,000 and 33,000 falling per m2 in the low and high ovisac treatments, respectively. Resulting infestation rates on Carolina hemlock seedlings were extremely low and well below damage threshold levels. Although A. tsugae crawlers were well distributed across the 1 m2 gridded glue sheets placed at the bottom of each cage, hot spots of unusually high crawler density did occur in both experiments. This rain-down technique shows potential for use in an operational tree-breeding program where screening large numbers of hemlock seedlings for resistance to A. tsugae is required.

Thousand cankers disease, caused by the walnut twig beetle (Pityophthorus juglandis Blackman) and an associated fungal pathogen (Geosmithia morbida M. Kolarík, E. Freeland, C. Utley, and N. Tisserat), threatens the health and commercial use of eastern black walnut (Juglans nigra L.), one of the most economically valuable tree species in the United States. Effective phytosanitary measures are needed to reduce the possibility of spreading this insect and pathogen through wood movement. This study evaluated the efficacy of heat treatments and debarking to eliminate P. juglandis and C. morbida in J. nigra logs 4-18 cm in diameter and 30 cm in length. Infested logs were steam heated until various outer sapwood temperatures (60, 65, and 70 degrees C in 2011; 36, 42, 48, 52, and 56 degrees C in 2012) were maintained or exceeded for 30-40 min. In 2011, all heat treatments eliminated G. morbida from the bark, but logs were insufficiently colonized by P. juglandis to draw conclusions about treatment effects on the beetle. Debarking did not ensure elimination of the pathogen from the sapwood surface. In 2012, there was a negative effect of increasing temperature on P. juglandis emergence and G. morbida recovery. G. morbida did not survive in logs exposed to treatments in which minimum temperatures were 48 degrees C or higher, and mean P. juglandis emergence decreased steadily to zero as treatment minimum temperature increased from 36 to 52 degrees C. A minimum outer sapwood temperature of 56 degrees C maintained for 40 min is effective for eliminating the thousand cankers disease vector and pathogen from walnut logs, and the current heat treatment schedule for the emerald ash borer (60 degrees C core temperature for 60 min) is more than adequate for treating P. juglandis and G. morbida in walnut firewood.

The redbay ambrosia beetle (Xyleborus glabratus Eichhoff) is an invasive pest and vector of the pathogen that causes laurel wilt disease in Lauraceous tree species in the eastern United States. This insect uses olfactory cues during host finding, but use of visual cues by X. glabratus has not been previously investigated and may help explain diameter-related patterns in host tree mortality. The objective of this study was to determine whether X. glabratus females visually detect silhouettes of tree stems during host finding and are more likely to land on large diameter stems than smaller ones. Three field experiments were conducted in which stem silhouettes (black cylinders or standing nonhost pines) of varying diameters and identical capture surface areas were baited with essential oil lures. The Log10-transformed number of X. glabratus trapped per week increased as a function of silhouette diameter in 2011 and 2012, using artificial silhouette diameters ranging 2-18 and 3-41 cm, respectively. When lures and capture surfaces were attached to standing pines ranging 4-37 cm in diameter, a positive relationship between Log10(X. glabratus trap catch) and stem diameter was modeled using nonlinear quadratic plateau regression and indicated a diameter above which visual attraction was not enhanced; however, there was not a maximum diameter for enhanced X. glabratus attraction that was generally consistent across all experiments. These results 1) indicate that X. glabratus incorporates visual information during host finding, 2) help explain diameter-related patterns of redbay (Persea borbonia (L.) Sprengel) mortality observed during laurel wilt epidemics, and 3) are applicable to the management of this forest pest.

In 2007-2008, we examined the flight responses of Monochamus titillator (F.) complex [M. titillator, Monochamus carolinensis (Olivier), and any possible hybrids], Monochamus scutellatus (Say), Monochamus clamator (LeConte), Monochamus obtusus Casey, and Monochamus mutator LeConte (Coleoptera: Cerambycidae) to multiple-funnel traps baited with and without host volatiles and bark beetle pheromones. Experiments were conducted in mature pine (Pinus) stands in Alberta (Canada), and Arkansas, Arizona, California, Florida, Idaho, Michigan, Montana, New Hampshire, North Carolina, Ohio, Oregon, Tennessee, Utah, and Wisconsin (United States). At each location, traps were deployed in 10 replicate blocks of four traps per block. The trap treatments were: 1) blank control; 2) ipsenol and ipsdienol; 3) ethanol and alpha-pinene; and 4) a quaternary blend of ipsenol, ipsdienol, ethanol, and alpha-pinene. All five species or species complex of Monochamus preferred traps baited with the quaternary blend over all other treatments. The consistency of these results across such a large geographic area suggests that similar selection pressures may be acting on Monochamus spp. in pine forests, regardless of variation in stand composition and climatic conditions. Our results suggest that multiple-funnel traps baited with the quaternary blend ofipsenol, ipsdienol, ethanol, and alpha-pinene may be highly effective for monitoring various Monochamus spp. in pine forests of North America, and may have utility in trapping and detection programs in North America and overseas.

The influence of site and stand conditions on pine false webworm (Acantholyda erythrocephala [L.], Hymenoptera: Pamphiliidae) population densities and host damage was evaluated in 22 eastern white pine (Pinus strobus L.) stands in northern New York State. Mean pine false webworm density was positively related to stand size (ha) and inversely related to soil silt content (A-horizon) after holding stand size constant. Percent radial growth loss (during the first five years after defoliation began) was inversely related to soil carbon content (B-horizon) and inversely related to fine sand content (A-horizon) after holding B-horizon carbon constant. Severe radial growth suppression (missing or discontinuous growth rings) and white pine mortality were inversely related to live crown ratio. The frequency of trees with missing growth rings was inversely related to soil nitrogen (A-horizon) after holding live crown ratio constant. Stands located on sandy glacial lake shoreline/delta deposits had more coarsely textured soils with lower levels of organic matter and nitrogen and had slower height growth rates, lower tree diversity, greater relative dominance of white pine, and higher levels of pine false webworm defoliation than stands on adjacent landforms. These results may be useful to foresters managing eastern white pine stands in areas where similar site and stand conditions predominate and pine false webworm occurs.

As a measure of cold hardiness, we tested the supercooling points or freezing temperatures of individual hemlock woolly adelgids ( Adelges tsugae Annand) collected from 15 locations across the north to south range of the adelgid in eastern North America at different times during two winters. Adelgids from the northern interior locations with USDA hardiness zones of 5B–6B had lower supercooling points than adelgids from more southern or more coastal locations (zones 7A and 6B), where minimum winter temperatures were higher. Supercooling points reached a minimum in February in northern but not in southern locations. Laboratory experiments demonstrated that adelgids exposed to colder temperatures (−12 °C) had lower supercooling points after 3 d and adelgids held at 10 °C had higher supercooling points than did adelgids held at 2 °C for the same period. Extending these periods to 7 d produced no further change in supercooling points. Adelgids at northern sites had much lower supercooling points in February 2015 following at least 10 d of much colder weather than adelgids from those same sites in February 2016 following much warmer weather. The induction of cold hardiness produced much year-to-year variation in cold hardiness, especially in northern sites, in addition to concurrently and previously demonstrated genetic differences in cold hardiness between northern and southern adelgid populations. Consequently, the cold temperatures required to kill hemlock woolly adelgids will vary year to year and week to week based on exposure to prior temperatures.

Coleophora klimeschiella Toll, whose larvae feed as case bearers on the foliage of Russian thistle, Salsola iberica Sennen and Pau, was introduced into quarantine in the U. S. in 1975. Detailed oviposition and larval feeding tests were conducted during 1975–76 on closely related plants and crop and ornamental species. Although eggs were laid on several non-host plant species, the insect was not able to complete larval development on any plant tested except Russian thistle. Coleophora klimeschiella has been approved for field release by state and federal agencies.