D. R. Smitley

Interspecific variation in resistance to emerald ash borer (Coleoptera: Buprestidae) among North American and Asian ash (Fraxinus spp.)

Abstract We conducted a 3-yr study to compare the susceptibility of selected North American ash and an Asian ash species to emerald ash borer, Agrilus planipennis Fairmaire, an invasive wood-boring beetle introduced to North America from Asia. Because of a coevolutionary relationship between Asian ashes and emerald ash borer, we hypothesized an Asian ash species, Manchurian ash, is more resistant to the beetle than its North American congeners. Consistent with our hypothesis, Manchurian ash experienced far less mortality and yielded far fewer adult beetles than several cultivars of North American green and white ash. Surprisingly, a black ash (North American) × Manchurian ash hybrid was highly susceptible to emerald ash borer, indicating this cultivar did not inherit emerald ash borer resistance from its Asian parent. A corollary study investigated the efficacy of soil-applied imidacloprid, a systemic, neonicotinoid insecticide, for controlling emerald ash borer in each of the five cultivars. Imidacloprid had no effect on emerald ash borer colonization of Manchurian ash, which was low in untreated and treated trees. In contrast, imidacloprid did enhance survival of the North American and hybrid cultivars and significantly reduced the number of emerald ash borer adults emerging from green and white ash cultivars. We identify a possible mechanism of resistance of Manchurian ash to emerald ash borer, which may prove useful for screening, selecting, and breeding emerald ash borer-resistant ash trees.

Progression of Ash Canopy Thinning and Dieback Outward from the Initial Infestation of Emerald Ash Borer (Coleoptera: Buprestidae) in Southeastern Michigan

Abstract Our objective was to characterize the rate at which ash (Fraxinus spp.) trees decline in areas adjacent to the leading edge of visible ash canopy thinning due to emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). Trees in southeastern Michigan were surveyed from 2003 to 2006 for canopy thinning and dieback by comparing survey trees with a set of 11 standard photographs. Freeways stemming from Detroit in all directions were used as survey transects. Between 750 and 1,100 trees were surveyed each year. A rapid method of sampling populations of emerald ash borer was developed by counting emerald ash borer emergence holes with binoculars and then felling trees to validate binocular counts. Approximately 25% of the trees surveyed for canopy thinning in 2005 and 2006 also were sampled for emerald ash borer emergence holes using binoculars. Regression analysis indicates that 41–53% of the variation in ash canopy thinning can be explained by the number of emerald ash borer emergence holes per tree. Emerald ash borer emergence holes were found at every site where ash canopy thinning averaged >40%. In 2003, ash canopy thinning averaged 40% at a distance of 19.3 km from the epicenter of the emerald ash borer infestation in Canton. By 2006, the point at which ash trees averaged 40% canopy thinning had increased to a distance of 51.2 km away from Canton. Therefore, the point at which ash trees averaged 40% canopy thinning, a state of decline clearly visible to the average person, moved outward at a rate of 10.6 km/yr during this period.

Parasitoids and Pathogens of Japanese Beetle (Coleoptera: Scarabaeidae) in Southern Michigan

Abstract The density of Japanese beetle (Popillia japonica Newman) and the prevalence of its natural enemies were evaluated in southern Michigan. Third instars were collected in spring and fall and adults during the summer of 1999 and 2000 at 11 golf courses. Larvae were also collected once in fall of 2000 from 24 additional sites including golf courses (n = 8), blueberry farms (n = 7) and low-maintenance turf (n = 9). Larval density in the irrigated rough at the 11 primary golf course sites averaged 9.5/0.1 m2 (range, 3.7–21.0). At the 24 additional sites, where habitat was more diverse, Japanese beetle larval density averaged 2.9/0.1 m2 (range, 0.60–14.4). The larval parasitoid Tiphia vernalis Rohwer and the adult parasitoid Istocheta aldrichi (Mesnil) were absent from all sites in this study. Cephaline gregarines (Stictospora sp.) were the most common parasites, infecting 36.1% of all larvae in fall of 2000. The microsporidean Ovavesicula popilliae Andreadis was absent at all but two locations near Kalamazoo, MI. The bacterial pathogen Paenibacillus popilliae (Dutky) and entomopathogenic nematodes were uncommon, infecting <1% of larvae. Overall, two parasites (T. vernalis and I. aldrichi) and two pathogen (O. popilliae), reported to be widespread and epizootic in some eastern states, were absent or nearly so (O. popilliae was found at two of 35 locations) in Michigan. Stictospora sp. was found at most locations in Michigan (25/36) where Japanese beetle infestations have been active for more than 20 yr, but was scarce or absent from areas where Japanese beetle has become established in the last 10 yr.

Predation of Ataenius spretulus (Coleoptera: Scarabaeidae) Eggs and Grubs by Species of Carabidae and Staphylinidae on Golf Courses in Michigan

Abstract Ataenius spretulus (Haldeman) (Coleoptera: Scarabaeidae) is more abundant and causes greater damage to golf course fairways than roughs. An inverse relationship between the density of predatory insects and the density of A. spretulus grubs on golf courses was previously reported. Here we investigate if the most abundant predators found on golf courses consume A. spretulus eggs and grubs. Eight of the most common species of carabids and staphylinids were individually placed into petri dishes containing insect eggs and A. spretulus grubs. Most carabids and staphylinids except Apocellus sphaericollis (Say) consumed immature A. spretulus. Harpalus affinus (Schrank) adults and Philonthus sp. larvae consumed 100% of available A. spretulus grubs in all replicates. Natural predation was measured by the release and recovery of A. spretulus grubs in the field. In 1999, more grubs were naturally removed from soil cores in the rough compared with the fairway. In 2000, more grubs were naturally removed from unrestricted soil cores compared with soil cores covered to exclude surface predators. In a separate field experiment in 2000, the density of carabid and staphylinid adults was manipulated using directional barriers around field plots. Simple decrease of adult predators did not lead to an increase in grub infestation. More work is needed to evaluate the significance of predation on A. spretulus eggs and grubs by carabid and staphylinid larvae.

REVISION OF THE GENUS STICTOSPORA AND DESCRIPTION OF STICTOSPORA VILLANI, N. SP. (APICOMPLEXA: EUGREGARINIDA: ACTINOCEPHALIDAE) FROM LARVAE OF THE JAPANESE BEETLE, POPILLIA JAPONICA (COLEOPTERA: SCARABAEIDAE), IN MICHIGAN

Stictospora villani n. sp. is described from larvae of the Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae) from southern Michigan. Stictospora villani is distinguished from known species of the genus by differences in gamont size and by structural details of the epimerite. In general, S. villani is smaller than other known species of the genus and possesses an epimerite with a margin of 20–24 sympetalous, pendulate, narrowly to very narrowly elliptoid lamina. Previously described species are characterized by epimerites with notably fewer marginal lamina. A heretofore unrecognized protistan is diagnosed from the coelomic fat bodies and tentatively placed within the Neogregarinorida. We conclude that previous workers have mistaken this neogregarine for the gametocyst and oocyst of Stictospora, which are described in this study for the first time. The generic diagnosis of Stictospora is revised to encompass the epimeritic variation of its constituent species and to correctly reflect the morphology of the oocyst.

Native Vaccinium spp. and Gaylussacia spp. infested by Rhagoletis mendax (Diptera: Tephritidae) in the Great Lakes Region: a potential source of inoculum for infestation of cultivated blueberries.

Abstract In this study, we addressed the question of whether or not native stands of blueberry (Vaccinium spp.) and/or huckleberry (Gaylussacia spp.) support populations of blueberry maggot, Rhagoletis mendax Curran, in the Great Lakes region. Infestation of commercial blueberries by the blueberry maggot, R. mendax, is a serious problem in many areas where blueberries are grown. In the past 10–20 yr, commercial highbush blueberry, Vaccinium corymbosum L., production has expanded into places such as southern Ontario and southern Quebec where blueberry maggot had not previously been reported. In the mid-1990s, isolated infestations of commercial highbush blueberry were reported in southern Ontario. Because R. mendax was not considered endemic to that area, it was widely assumed that the pests had come into the fields via movement from exotic localities. Here we present an alternative hypothesis, that the blueberry maggots infesting newly established highbush plantations are derived from native blueberries growing in the vicinity. To test this hypothesis, in 1997–1999, we sampled potential native hosts for R. mendax (Vaccinium spp. and Gaylussacia spp.) from 31 localities in the Great Lakes region, primarily in Michigan and Ontario. R. mendax was reared from fruits of native hosts collected at four sites in Michigan and one site each in Ontario, Indiana, and Ohio. V. corymbosum was the predominant host infested, with infestation of this host observed at five of the seven sites. However, two huckleberry species [Gaylussacia baccata (Wangenheim) K. Koch, and Gaylussacia dumosa (Andersson) Torrey & Gray] had the highest rates of infestation that we observed (25.4 and 17.6%, respectively). These data represent the first published reports of R. mendax infesting native host plants in the Great Lakes region, and support the hypothesis that infestations observed in commercial fields may have originated from infested native host plants.

Distribution and adult activity of Popillia quadriguttata (Coleoptera: Scarabaeidae) on golf courses in Korea

Abstract Japanese beetle traps baited with the Popillia japonica Newman (Coleoptera: Scarabaeidae) pheromone lure and a eugenol feeding attractant were placed at five golf courses in Korea to determine how well they work for detecting activity of a closely related species, Popillia quadriguttata (F.) (Coleoptera: Scarabaeidae), a turf pest in Korea. The traps also were used to determine the time of day and time of year that P. quadriguttata is most active. Nineteen scarab species of 13 genera were attracted to the Japanese beetle traps with P. quadriguttata clearly being the most abundant (383 beetles per trap), followed by Adoretus tenuimaculatus Waterhouse (10 per trap), Popillia flavosellata Fairmaire (seven per trap), Exomala orientalis Waterhouse (four per trap), and Maladera japonica (two per trap). Other scarab species were trapped at a rate of <1.0 per trap. Popillia quadriguttata adults were active over a 5-wk period in late June and early July. At Yongwon Golf Club in 2002, peak adult activity was during the last week of June in visual counts and ≈1 wk later in the Japanese beetle traps. In Korea, P. quadriguttata adults are most active between 12:00 p.m. and 4:00 p.m. This information should be helpful to golf course superintendents in Korea and to entomologists interested in finding natural enemies of P. quadriguttata to evaluate as potential biocontrol organisms for the very closely related species, the Japanese beetle.

Efficacy of Soil-Applied Neonicotinoid Insecticides for Long-term Protection Against Emerald Ash Borer (Coleoptera: Buprestidae)

ABSTRACT Protection of green ash trees (Fraxinus pennsylvanica Marshall) from the emerald ash borer (EAB), Agrilus planipennis Fairmaire, by soil applications of neonicotinoids (imidacloprid, clothianidin, and dinotefuran) was tested at five locations between 2005 and 2013. Application rate and spring versus fall application dates were evaluated in tests with neighborhood street trees and in one plantation of 65 ash trees. Insecticide treatments of ash trees at all five sites were initiated as the leading edge of the EAB invasion began to kill the first ash trees at each location. Trees were treated and evaluated at each site for 4 to 7 yr. Spring applications of imidacloprid were more efficacious than fall applications. Application rates of 0.8 g a.i./cm dbh or greater per year gave a higher level of protection and were more consistent than rates of 0.56 g a.i./cm dbh per year or less. The number of years between the first observation of canopy loss due to EAB and death of most of the control trees varied from three to seven years among test sites, depending on how many non-treated ash trees were nearby.

Identification of Western Flower Thrips

Western flower thrips (WFT) is distinguished from other Frankliniella species by the shape of antennal segment III, the size of the pronotal anteroangular setae, the position of the ocelli and interocellar setae, and the complete comb of posteromarginal setae on tergum VIII. The position of the interocellar setae, which arise from just inside the triangle formed by lines connecting the outside edge of the three ocelli, is critical because it is used to combine species into working groups within the genus. The distance between the posterior ocelli is more than twice their diameter. The base of antennal segment III is without a sharp angulation and the pronotal anteroangular setae are almost as long as the anteromarginal setae. These characteristics were documented with scanning electron micrographs (SEM). Open image in new window Figure 1 SEM of WFT showing diagnostic features; a, ovipositor; b, antenna; c, head and thorax; d, forewings.

Impact of Bacillus thuringiensis Application on Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) and LdNPV-Induced Mortality of Gypsy Moth (Lepidoptera: Lymantriidae)

Abstract The effect of aerial application of Bacillus thuringiensis variety kurstaki Berliner ( Btk) on mortality of gypsy moth larvae caused by the entomopathogens Entomophaga maimaiga Humber, Shimazu, & Soper, and the gypsy moth nucleopolyhedrosis virus ( LdNPV) was evaluated. Three sites in 1997 and four sites in 1998 were established in a randomized complete block design. Larvae were collected weekly to determine the proportion infected with E. maimaiga and LdNPV. In 1997, epizootics of E. maimaiga in control plots boosted infection rates (61%) to levels twice that in Btk-treated plots (33%). Postseason egg mass density and defoliation did not differ between treatments, indicating population reduction early in the season by Btk or late in the season by E. maimaiga was equivalent. Few larvae became infected with LdNPV in 1997, probably because of the relatively low densities of gypsy moth larvae. In 1998, E. maimaiga was again more active in control plots than in Btk-treated plots, but dry weather conditions suppressed activity of E. maimaiga in all plots compared with 1997. LdNPV was also more active in control plots than in Btk-treated plots. On the peak infection date, infection levels in control plots (26%) were sixfold higher than in Btk-treated plots (4%). Despite greater LdNPV activity in control plots in 1998, aerial application of Btk was much more effective than natural LdNPV in suppressing gypsy moth populations. Final egg mass counts were 89% lower in Btk-treated plots compared with control plots. E. maimaiga and LdNPV disease prevalence increased with increases in larval density. Early spring inoculum levels and weather conditions were similar for all plots. Therefore, reduced infection levels in Btk-treated plots were most likely the result of a slower rate of spread of E. maimaiga and LdNPV among larvae in these plots where the larval density was reduced 5- to 10-fold from Btk. When E. maimaiga is active, as observed in 1997, low density populations of gypsy moth may be held in check by E. maimaiga as well as by Btk applications. However, unusually dry conditions, like we observed in 1998, may suppress E. maimaiga activity and allow gypsy moth populations to build.