Michael E. Montgomery

Mitochondrial DNA from Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Suggests Cryptic Speciation and Pinpoints the Source of the Introduction to Eastern North America

Abstract The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is an introduced pest of unknown origin that is causing severe mortality to hemlocks (Tsuga spp.) in eastern North America. Adelgids also occur on other Tsuga species in western North America and East Asia, but these trees are not significantly damaged. The purpose of this study is to use molecular methods to clarify the relationship among hemlock adelgids worldwide and thereby determine the geographic origin of the introduction to eastern North America. Adelgids were collected from multiple locations in eastern and western North America, mainland China, Taiwan, and Japan, and 1521 bp of mitochondrial DNA was sequenced for each sample. Phylogenetic analyses suggest that the source of A. tsugae in eastern North America was likely a population of adelgids in southern Japan. A single haplotype was shared among all samples collected in eastern North America and samples collected in the natural range of T. sieboldii in southern Honshu, Japan. A separate adelgid mitochondrial lineage was found at higher elevations in the natural range of T. diversifolia. Adelgids from mainland China and Taiwan represent a lineage that is clearly diverged from insects in North America and Japan. In contrast to eastern North America, there is no conclusive evidence for a recent introduction of A. tsugae into western North America, where multiple haplotypes are found. Implications for hemlock woolly adelgid control, taxonomy, and plant–insect coevolution are discussed.

Ethanol and other host-derived volatiles as attractants to beetles that bore into hardwoods

Ethanol, methanol, acetone, and acetaldehyde—chemicals identified in the inner bark of living trees—were used to bait vane traps placed in crowns of oak trees in Connecticut. Ethanol-baited traps caught more cerambycid, scolytid, and clerid beetles than unbaited traps. Buprestidae were not attracted to ethanol. Acetaldehyde and acetone were not attractive to any family. A mixture of ethanol, methanol, and acetaldehyde was no more attractive than ethanol alone. The vane traps were very effective at catching Cerambycidae and Scolytidae, but ineffective compared to sticky panels at catching Buprestidae.

Evaluation of hemlock (Tsuga) species and hybrids for resistance to Adelges tsugae (Hemiptera: Adelgidae) using artificial infestation.

ABSTRACT Hemlock (Tsuga) species and hybrids were evaluated for resistance to the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae). The adelgid was accidentally introduced from Asia to the eastern United States, where it is causing widespread mortality of the native hemlocks, Tsuga canadensis (L.) Carrière and Tsuga caroliniana Engelm. These two native species plus the Asian species Tsuga chinensis (Franch.) E. Pritz and T. dumosa (D.Don) Eichler and Tsuga sieboldii Carrière, and the hybrids T. chinensis × T. caroliniana and T. chinensis × T. sieboldii, were artificially infested with the crawler stage of A. tsugae in the early spring 2006 and 2007. After 8 or 9 wk—when the spring (progrediens) generation would be mature—counts were made of the adelgid. In both years, the density of A. tsugae was highest on T. canadensis, T. caroliniana, and T. sieboldii; lowest on T. chinensis; and intermediate on the hybrids. On T. chinensis and the T. chinensis hybrids, fewer adelgids settled, fewer of the settled adelgids survived, and the surviving adelgids grew slower. Thus, the nature of the host resistance is both nonpreference (antixenosis) and adverse effects on biology (antibiosis). Tree growth (height) was associated with resistance, but no association was found between time of budbreak and resistance that was independent of the taxa. Many of the hybrids grow well, have attractive form, and are promising as resistant landscape alternatives for the native hemlocks.

FOLIAGE DAMAGE DOES NOT AFFECT WITHIN‐SEASON TRANSMISSION OF AN INSECT VIRUS

Gypsy moth defoliation of oak trees has been shown to lead to increased tannin levels, which, in turn, lead to reduced gypsy moth growth and fecundity. In laboratory experiments, increased tannin levels can interfere with the transmission of a virus that is consumed by larvae on oak foliage, and high mortality rates of larvae in the field are sometimes associated with low levels of defoliation. These latter results have led to the suggestion that gypsy moth defoliation may cause reduced mortality attributable to the virus by elevating oak tannin levels. In a series of field experiments, we directly tested the hypothesis that gypsy moth defoliation of oaks leads to reduced virus transmission rates. In each of three study years, in oak forests with almost no naturally occurring gypsy moths or virus, we measured virus transmission rates in gypsy moths feeding on oaks, with and without experimental defoliation. By carefully synchronizing our experiments with the phenology of natural gypsy moth populations, we mimicked natural virus transmission processes during that part of the gypsy moth life cycle when virus transmission occurs. In our experiments, there was no effect of gypsy moth defoliation on tannin levels; consequently, virus transmission in both the field and the lab was unaffected by defoliation. Although we did observe increased tannin levels on more severely defoliated oak trees in one of two naturally defoliated oak stands late in the season, virus transmission had virtually ceased by that time. Our results suggest that gypsy moth defoliation does not affect tannin levels early enough in the larval season to have a measurable effect on the interaction between the gypsy moth and its nuclear polyhedrosis virus.

Oviposition, Development, and Feeding of Scymnus (Neopullus) sinuanodulus (Coleoptera: Coccinellidae): a Predator of Adelges tsugae (Homoptera: Adelgidae)

Abstract The hemlock woolly adelgid, Adelges tsugae Annand, is a major threat to hemlocks in the eastern United States. As part of efforts to control this pest, Scymnus ( Neopullus ) sinuanodulus Yu et Yao, a potential predator, was collected from hemlocks in Yunnan, China. Three shipments were imported during 1996 and 1997 to a quarantine laboratory to study the beetle’s biology. Beetles began oviposition immediately after transferal from 5°C in the spring, ceased oviposition by June, and laid the same number of eggs, whether egg laying began in February or in April. Two-year-old beetles laid as many eggs per year as 1-yr-old beetles. We observed only one generation per year. Yearly fecundity averaged 130 eggs with a maximum of 200 per female. Newly emerged beetles remained preovipositional until the following spring, but could be induced to oviposit in the fall by prior exposure to 5 or 10°C for 1.5 mo. The egg, larval (four instars), and pupal stages lasted 10, 20, and 10 d, respectively, at 20°C. From egg to adult took 73, 40, and 35 d at 15, 20, and 25°C, respectively. Larval survival was only 5% at 25°C. Both larvae and adults fed on all stages of A. tsugae, but larvae grew faster with much higher survival on adelgid eggs, and could not complete development on adelgid nymphs alone. When given adelgid eggs, the beetles laid more eggs initially; however, adelgid nymphs seem to satisfy nutritional requirements for oviposition. Laboratory-reared beetles were similar to field-collected beetles in oviposition, fecundity, feeding, survival, and development.

Radiative properties of hardwood leaves to ultraviolet irradiation

Spectral reflectance and transmittance of leaves to ultraviolet irradiation were determined under laboratory conditions for seven species of hardwood trees, namely red oak (Quercus rubra, L), black oak (Q. velutina, Lamarch), white oak (Q. alba, L.), sugar maple (Acer saccharum), Norway maple (A. plantanoides), hickory (Carya tomemtosa), sweetgum (Liquidambar styraciflua), and black oak litter. The experimental system consisted of a solar simulator, an integrating sphere, and a spectroradiometer. Experiments were repeated three to five times for both adaxial and abaxial surfaces of fresh leaves chosen at randomly. The spectral distributions and simple averages of the radiative properties in the wavelength ranges of ultraviolet-B (UV-B, 280–320 nm) and ultraviolet-A (UV-A, 320–400 nm) were determined. The spectral distributions of reflectance were similar between adaxial and abaxial surfaces, although the magnitude varied among tree species. Leaf reflectance was very low for the ultraviolet spectrum in general and varied among species and between adaxial and abaxial surfaces. It was generally higher over the UV-A waveband compared to UV-B, and higher on the abaxial than adaxial surface. The broadband reflectance in the UV-A range (over all species) was 5.0 and 3.9% for abaxial and adaxial surface, respectively, compared to 3.5 and 2.8% in UV-B. The transmittance through leaves was extremely small in the UV-B (<0.1%) and nearly zero in the UV-A spectral range. Consequently, the absorptance of ultraviolet radiation by leaves, as determined from the measured reflectance and transmittance, was quite high, being more than 90% for all the combinations of species and wavebands examined. The reported results are useful for studies requiring spectral radiative properties of the examined leaves with respect to ultraviolet irradiation.

A New Species of Laricobius (Coleoptera: Derodontidae) From Japan With Phylogeny and a Key for Native and Introduced Congeners in North America

ABSTRACT Laricobius osakensis Montgomery and Shiyake sp. nov., collected from Adelges tsugae Annand on hemlock [Tsuga sieboldii Carr. and Tsuga diversifolia (Maxim.) Mast.] in Japan, is described and illustrated. The new species was collected from several localities on Honshu, Shikokou, and Kyushu Islands. The genus has not been reported previously from Japan. Morphological features, a molecular phylogeny, and diagnostic DNA sites are provided to distinguish this new species from previously described species of the genus. Because of plans to release L. osakensis for the biological control of A. tsugae in eastern North America, a key and discussion are provided to differentiate it from the native North American species, Laricobius nigrinus Fender, Laricobius laticollis Fall, and Laricobius rubidus LeConte, and from two previously imported species—Laricobius erichsonii Rosenhauer, which is endemic in Europe, and Laricobius kangdingensis Zilahi-Balogh & Jelinek, which is endemic in China.

Life-cycle nitrogen budget for the gypsy moth, Lymantria dispar, reared on artificial diet

Abstract Lymantria dispar larvae were reared on a wheat germ-based artificial diet from egg eclosion until pupation. Utilization efficiency of dietary nitrogen underwent an age-specific decrease from 75% in the first instar to 54 and 43% for last-instar female and male larvae, respectively. Relative rates (mg/day/mg biomass) of nitrogen consumption and assimilation also decreased during larval development, but the excretion rate of nitrogen was constant for all instars and both sexes. Larval % nitrogen decreased as the larvae matured, while the percentage in the frass increased. These data suggest that need for nitrogen decreases as the larva matures. While L. dispar is comparatively inefficient at assimilating dietary nitrogen, over one-half of that assimilated by the female larva is transferred to egg production by the adult.

Effects of Foliar Phenolics and Ascorbic Acid on Performance of the Gypsy Moth (Lymantria Dispar)

Abstract We investigated the potential for interactive effects between foliar ascorbic acid and phenolics on performance of the gypsy moth ( Lymantria dispar ). In our first study, feeding bioassays with neonate larvae and fourth instars were used to examine larval performance on five host species in relation to concentrations of ascorbic acid and phenolics. In a second study, we supplemented leaves with ascorbic acid and phenolics to assess both direct and interactive effects on fourth instars. Results revealed that gypsy moth performances (e.g. growth, development rates) varied significantly across host species and in relation to phenolic compounds in aspen. Ascorbic acid, however, neither directly nor indirectly (via interaction with phenolics) influenced larval performance.

Feeding Preference of Three Lady Beetle Predators of the Hemlock Woolly Adelgid (Homoptera: Adelgidae)

Abstract In a laboratory study, we tested the feeding preferences of three coccinellid predators of hemlock woolly adelgid, Adelges tsugae Annand, an introduced pest of hemlock in the eastern United States. The species tested were Sasajiscymnus tsugae Sasaji & McClure (formerly Pseudoscymnus tsugae) from Japan, Scymnus ningshanensis Yu & Yao from China, and Harmonia axyridis (Pallas), a generalist species introduced from Asia that is currently widespread in eastern hemlock, Tsuga canadensis Carriere, forests. We measured the feeding preference of each beetle species when given the choice of A. tsugae and either 1) Pineus strobi (Hartig) on Pinus strobus L.; 2) Adelges laricis Vallot on Larix decidua Mill.; 3) Adelges cooleyi (Gillette) on Pseudotsuga menziesii (Mirb.) Franco; or 3) Paraprociphilus tessellatus (Fitch) on Alnus serrulata (Ait.) Willd. We evaluated beetle preference for adults, nymphs, and eggs of each prey species. Generally, when adult or nymphal prey stages were compared, S. tsugae preferred A. tsugae adults to P. strobi, A. cooleyi, A. laricis, and P. tessellatus. S. ningshanensis showed less preference between adelgid species, but it did not prefer P. tessellatus nymphs. When preferences for adelgid eggs were assayed, S. tsugae and S. ningshanensis showed no preference between A. tsugae and A. cooleyi or P. strobi, but S. tsugae did prefer A. tsugae to A. laricis. Larvae of S. tsugae were unable to survive on P. tessellatus nymphs. H. axyridis adults readily consumed both A. tsugae and P. tessellatus, but H. axyridis larvae did not complete their life cycle on A. tsugae. Our host range tests suggest that S. ningshanensis and S. tsugae may feed on several species of Adelgidae and that A. tsugae is often preferred.