Search

After decades of multiyear defoliation episodes in southern New England, Lymantria dispar dispar (previously gypsy moth) populations diminished with the appearance of the L. dispar fungus in 1989. Multiyear defoliations did not occur again until 2015–2018. To assess the impact of the return of multiyear defoliations, we examined 3095 oaks on 29 permanent study areas in Connecticut and Rhode Island that were established at least 11 years before the latest outbreaks. Pre-defoliation stand-level oak mortality averaged 2% (3-year basis). Post-defoliation mortality did not differ between managed and unmanaged stands but was much higher in severely defoliated stands (36%) than in stands with moderate (7%) or low to no defoliation (1%). Pre-defoliation mortality of individual trees differed among species, was lower for larger diameter trees and on unmanaged than managed stands. Post-defoliation mortality on plots with no to moderate defoliation was similar to pre-defoliation mortality levels. Following multiyear defoliations, white oak (Quercus alba L.) mortality was higher than for northern red oak (Quercus rubra L.) and black oak (Q. velutina Lam.). There was weak evidence that mortality was elevated on stands with higher basal area following severe defoliation. Natural resource managers should not assume that oaks that survived earlier multiyear defoliations episodes will survive future multiyear outbreaks, possibly because trees are older.

For regulatory purposes, the name ‘Asian gypsy moth’ refers to a group of closely related Asian Lymantria species and subspecies whose female moths display flight capability, a trait believed to confer enhanced invasiveness relative to the European gypsy moth, Lymantria dispar dispar, whose females are flightless. Lymantria albescens and Lymantria postalba are Asian gypsy moths occurring in the southern Ryukyu Islands and in the northern Ryukyu and adjacent Kyushu and Shikoku Islands of Japan, respectively. Although once considered subspecies of L. dispar, their status as distinct species, relative to the latter, is now well established. While postalba was subsequently considered a subspecies of L. albescens, largely on the basis of differences in forewing ground colour in males, both taxa were later given distinct species status by Pogue & Schaefer (2007) following their revision of the genus Lymantria. Here, we re‐examined the validity of this revised status through the sequencing of a large portion of the mitochondrial genome (c. 60%) and multiple nuclear marker genes [elongation factor 1‐alpha (Ef‐1α), wingless (Wgl), internal transcribed spacer 2 (ITS‐2), ribosomal protein S5 (RpS5)] in representative specimens of both taxa and other Lymantria species, including L. monacha, L. xylina, L. mathura and members of the L. dispar + L. umbrosa clade. A comparison of the number of substitutions in these genomic regions among the taxa we considered showed lower or equivalent variation between L. albescens and L. postalba compared with subspecies of L. dispar, for mitochondrial and nuclear sequences, respectively. This finding was reflected in the maximum likelihood trees generated independently for mitochondrial and nuclear data, where L. albescens and L. postalba formed, in both analyses, a short‐branch sister clade basal to the L. dispar + L. umbrosa clade. We further sequenced three markers [cytochrome c oxydase 1 (COI), EF‐1α, Wgl] in multiple L. albescens–L. postalba specimens collected along a south‐to‐north transect across the Ryukyu Arc and observed no clear distinction among the sampled specimens as a function of taxonomic designation. We conclude that L. albescens and L. postalba form a single species, with postalba representing a darker‐winged morph along an apparent south‐to‐north wing colour cline. Accordingly, L. postalba is relegated to synonymy under L. albescens (syn.n.).

Phenology models are useful tools in pest management interventions, biosecurity operations targeting alien invaders, and answering questions regarding the potential for range expansion/shift. The Gypsy Moth Life Stage model (GLS) has been used to predict the invasive range of the North American gypsy moth (Lymantria dispar dispar Linnaeus [Lepidoptera: Erebidae]) in North America and New Zealand. It has been used to examine the role of supra-optimal temperatures in range expansion/stasis/retraction. However, GLS has also been used where the target organism is the Asian subspecies L. d. asiatica Vnukovskij, despite observed differences between the predominant phenotypes of the two subspecies in the temperature requirements for egg hatch and the absence of egg phenology model parameters specific to the Asian phenotype. Here we describe the results of temperature and exposure duration on the timing of Asian gypsy moth egg hatch, and we present phenology model parameters for the Asian phenotype. Sum of squared differences (observed minus predicted day of median egg hatch) was reduced from 7,818 d2 (North American parameters) to 178 d2. Days of simulated median egg hatch differed from the observed days by 0–7 d (x¯=0.2; SD=3.1). The pattern of simulated egg hatch closely mimicked the irregular pattern of observed egg hatch from the temperature regimes of our experiment. Egg hatch is arguably the most important life cycle event in gypsy moth population suppression/eradication interventions and in estimating their potential invasive range. The model parameters described here produce accurate predictions of Asian gypsy moth egg hatch.

Estimates of absolute pest population density are critical to pest management programs but have been difficult to obtain from capture numbers in pheromone-baited monitoring traps. In this paper, we establish a novel predictive relationship for a probability (spTfer(r)) of catching a male located at a distance r from the trap with a plume reach D. spTferr=spTfer01+rD2, r≤Rmax0, r>Rmax, where spTfer(0) is the probability of catching an insect located next to the trap and Rmax is the maximum dispersal distance for the insect during the trapping period. The maximum dispersal distance for gypsy moth is known to be 1600 m. The probability of catching a gypsy moth male located next to a United States Department of Agriculture (USDA) milk carton pheromone-baited trap is 0.37, the overall probability of catching a male from the entire trapping area (Tfer) of ~800 ha is 0.0008, and plume reach of this trap is D = 26 ± 3 m. The equation for spTfer(r) is used to derive statistical upper and lower bounds (95% confidence interval) on the population density for the given value of a single trap catch. This combination of trap parameters appears to produce an effective trap: even a catch of 1 male provides meaningful lower and upper bounds on absolute population density. Applications in the management programs are discussed, and a look-up table is provided to translate the catches in USDA milk carton pheromone-baited traps to absolute population bounds, which can help design better management strategies.

All male gypsy moths, Lymantria dispar L., are capable of strong directed flight, but flight in females varies, increasing from west to east geographically across Eurasia. To better understand how the wings differ between female flight capable and flightless strains, a wing morphometric analysis of 821 gypsy moths from eight geographic strains (three Lymantria dispar dispar L., four Lymantria dispar asiatica Vnukovskij, one Lymantria dispar japonica Motschulsky) was performed. Body mass; length and width of both fore- and hindwing; and wing area, aspect, and loads were measured on both sexes from each strain. Gypsy moths were sexually dimorphic; females had a higher wing load, larger aspect ratios, bigger wing area, and heavier body mass than males. Wing loads of females, but not males, differed significantly among geographic strains and were lower in flight capable strains. Wing aspect was less variable within each sex among the strains. Female fore- and hindwing area were both larger in strains with strong directed flight capabilities compared with flightless strains, suggesting both fore- and hindwing areas play significant roles in flight. A logistic regression model using female forewing length and wing load correctly predicted the female flight capability of the source strains >97% of the time and may be a useful tool to use in conjunction with molecular methods for detecting introductions of Asian gypsy moth. None of the male morphometric wing characters were found to reliably predict the female flight capability of the source population.

In this study, Lymantria dispar dispar larvae, collected from three different localities in Turkey, were examined for the presence of inclusion bodies under phase contrast and electron microscopes. Inclusion bodies from infected larvae were subjected to polymerase chain reaction using the conserved primers for polyhedrin (polh), late expression factor 8 (lef-8) and late expression factor 9 (lef-9) genes. Sequence analysis confirmed that larvae collected from the three different localities contained multiple nucleopolyhedrosis viruses (MNPVs). These isolates were designated LdMNPV-T1, LdMNPV-T2 and LdMNPV-T3. Phylogenetic analyses of these isolates were performed using target genes polh, lef-8 and lef-9. Restriction endonuclease analysis of the three geographic isolates with EcoRI and PstI enzymes demonstrated some differences existed among the isolates. According to the EcoRI profile, the mean estimated size for the complete genome of each isolate (LdMNPV-T1, LdMNPV-T2 and LdMNPV-T3) was calculated to be approximately 170, 153 and 170kb, respectively. Insecticidal activities of each isolate were tested on L.d.dispar larvae using four different viral concentrations between 10(3) and 10(6)OBs/ml. Results showed that the mortalities for LdMNPV-T1, -T2 and -T3 ranged between 13-53%, 47-100% and 46-93%, respectively. The LC50 and LC95 values of LdMNPV-T2 were not significantly different from the respective corresponding values of the other two isolates. However, isolate LdMNPV-T2 killed larvae with a LC50 value that was lower than the other two isolates. Our results suggested there are promising LdMNPV isolates in Turkey that can be used for microbial control of L.d.dispar larvae.

Tympanal ears of female gypsy moths Lymantria dispar dispar (L.) (Lepidoptera: Erebidae: Lymantriinae) are reportedly more sensitive than ears of conspecific males to sounds below 20 kHz. The hypothesis is tested that this differential sensitivity is a result of sex-specific functional roles of sound during sexual communication, with males sending and females receiving acoustic signals. Analyses of sounds produced by flying males reveal a 33-Hz wing beat frequency and 14-kHz associated clicks, which remain unchanged in the presence of female sex pheromone. Females exposed to playback sounds of flying conspecific males respond with wing raising, fluttering and walking, generating distinctive visual signals that may be utilized by mate-seeking males at close range. By contrast, females exposed to playback sounds of flying heterospecific males (Lymantria fumida Butler) do not exhibit the above behavioural responses. Laser Doppler vibrometry reveals that female tympana are particularly sensitive to frequencies in the range produced by flying conspecific males, including the 33-Hz wing beat frequency, as well as the 7-kHz fundamental frequency and 14-kHz dominant frequency of associated clicks. These results support the hypothesis that the female L. dispar ear is tuned to sounds of flying conspecific males. Based on previous findings and the data of the present study, sexual communication in L. dispar appears to proceed as: (i) females emitting sex pheromone that attracts males; (ii) males flying toward calling females; and (iii) sound signals from flying males at close range inducing movement in females, which, in turn, provides visual signals that could orient males toward females.

The spectral sensitivity of the compound eye in three gypsy moth species from six different geographical regions (Lymantria dispar asiatica Vnukovskij [Asian gypsy moth], Lymantria dispar japonica Motschulsky [Japanese gypsy moth], and Lymantria dispar dispar L. [North American gypsy moth]) was tested electrophysiologically in the wavelength region 300-700 nm. For all moths examined, a maximum response occurred in the 480-520-nm range (blue-green region) with a shoulder peak occurring at 460 nm. A smaller, secondary peak was observed for both sexes at the 340-380-nm range, which is in the region considered behaviorally maximal in night-flying insects. No peaks in sensitivity were observed between 520 and 700 nm (red region) for any of the moths tested. Based on our retinal recording data, a short wavelength blocking filter with a transition wavelength near 500 nm should reduce gypsy moth attraction to artificial lighting sources. This would help reduce the number of Lymantria-infested ships traveling to and from foreign ports.

Gypchek is a gypsy nucleopolyhedrovirus (LdMNPV) product used for management of European gypsy moth (Lymantria dispar dispar L.) in the United States, primarily in areas where the use of broad-spectrum pesticides is not appropriate. Similar LdMNPV products are used in Russia for control of a flighted-female strain of Asian gypsy moth (Lymantria dispar asiatica Vnukovskij), an insect not yet established in the United States. Gypchek is a mixture of LdMNPV genotypic variants and is being developed further toward a single, high- potency genotype product that is effective against both European and Asian strains. We isolated 5 LdMNPV genotypic variants from Gypchek and, through diet incorporation bioassays, assessed their potencies for both a laboratory strain of European gypsy moth and a wild Asian gypsy moth strain. Bioassays conducted in the United States showed that 2 viral isolates, 122b and 122-HP, were about 3 times as potent as Gypchek against European gypsy moth. Bioassays conducted in Russia...

Males and females of the parasitoid wasp Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae) emerge en masse from gypsy moth, Lymantria dispar dispar (L.) (Lepidoptera: Noctuidae: Lymantriinae), host egg masses. Males engage females in a brief pre-copulatory ritual, mate, and then execute a post-copulatory ritual. We investigated mechanisms, functions, and fitness consequences of the pre- and post-copulatory ritual by high-speed cinematography, gas chromatographic-mass spectrometric analyses of volatile constituents on the insects' integument, and behavioral assays. Our data indicate that the mechanisms of the pre- and post-copulatory ritual are physical interactions rather than pheromone transfer. During the pre-copulatory ritual, the males put females into a trance-like state that persists for some time after copulation. Males attained a mating with in-trance females 9.5 times faster than with females that had come out of trance. Mated females with post-copulatory ritual experience did not remate, whereas females lacking that experience did. The total number of offspring and daughters did not differ between females with or without post-copulatory ritual experience or in relation to the duration of that ritual. The post-copulatory ritual functions as a form of mate guarding in that the male accelerates awakening of the in-trance female, which then rejects mating attempts by other males, ensuring his paternity.

Female gypsy moths, Lymantria dispar L., from 46 geographic strains were evaluated for flight capability and related traits. Males from 31 of the same strains were evaluated for genetic diversity using two polymorphic cytochrome oxidase I mitochondrial DNA restriction sites, the nuclear FS1 marker, and four microsatellite loci. Females capable of strong directed flight were found in strains that originated from Asia, Siberia, and the northeastern parts of Europe, but flight capability was not fixed in most strains. No flight-capable females were found in strains from the United States or southern and western Europe. Wing size and musculature were shown to correlate with flight capability and potentially could be used in predicting female flight capability. The mtDNA haplotypes broadly separated the gypsy moth strains into three groups: North American, European/Siberian, and Asian. Specific microsatellite or FS1 alleles were only fixed in a few strains, and there was a gradual increase in the frequency of alleles dominant in Asia at both the nuclear and microsatellite loci moving geographically from west to east. When all the genetic marker information was used, 94% of the individuals were accurately assigned to their broad geographic group of origin (North American, European, Siberian, and Asian), but female flight capability could not be predicted accurately. This suggests that gene flow or barriers to it are important in determining the current distribution of flight-capable females and shows the need for added markers when trying to predict female flight capability in introduced populations, especially when a European origin is suspected.