Attraction of male gypsy and nun moths to disparlure and some of its chemical analogues

Summary The attractive power of disparlure—the sex attractant of the gypsy moth (Lymantria/Porthetria dispar)—vs. four synthetic analogous epoxides was tested in 1972 in a pine forest near Heidelberg. With two levels of concentration in the traps (2 and 20 g), a total of 1112 nun moths (Lymantria/Porthetria monacha) and 257 gypsy moths were caught in 9 experiments. Approximately equal percentages of the two species were caught with a given compound. Disparlure was by far the most effective attractant. The other substances were between three and twenty times less effective. These experiments support the assumption that disparlure is also at least part of the sexual attractant of the nun moth. In two additional experiments, moth captures by a series of increasing disparlure concentrations (2–100 g/trap) were determined. The catches of both species increased nonlinearly with the bait concentration. The experiments are discussed with respect to new (unpublished) electrophysiological recordings from disparlure receptor cells in both species. Special attention is given to the supposed masking effect of the disparlure precursor (an olefin). This substance is ineffective as an attractant, but has been reported to reduce the attraction of gypsy moth males to disparlure or to live females. However, the olefin elicits excitatory reactions in the same type of receptor cell that responds to disparlure and the related epoxides. Furthermore, no masking of the electrophysiological response was observed with the receptor cells when the olefin was added to disparlure.Supported by the Deutsche Forschungsgemeinschaft.     

Electroantennogram and behavioural responses of the gypsy moth to enantiomers of disparlure and its trans analogues

The attractive power of both enantiomers of disparlure and its trans analog was tested electrophysiologically (electroantennogram = EAG) and behaviourally (whole organism response). EAG responses correlated very well with the behaviourally determined effectiveness sequence: cis(+)-disparlure was the most effective substance; the authentic racemic disparlure came second; cis(?)-disparlure inhibited the activity of cis(+)-disparlure; and trans enantiomers were not significantly different from the control. These results allow us to conclude that cis(+)-disparlure is the natural sex pheromone of the gypsy moth, and that the male antennae have a chiral receptor system in the antenna for the reception of the sex pheromone.     

Separation of translation and rotation by means of eye-region specialization in flying gypsy moths (Lepidoptera: Lymantriidae)

A partial functional specialization of eye regions in the visual control of flight was studied in male gypsy moths, Lymantria dispar,under open-loop conditions. When stimulated by means of a rotating striped drum, surrounding either the moth 's longitudinal or its transverse body axis, the induced torque response was always such as to compensate for a simulated translatory disturbance of flight, if the stimulus was restricted to the ventral visual field. If restricted to the lateral visual field(s), the response was always such as to compensate for a simulated rotatory disturbance. Though the conclusions refer to only a limited subset of visual stimuli the moths experience during free flight, the induced responses give reason to suppose that at least some of the simultaneous control of translation and rotation in free flight is based on a regional specialization of the compound eye.     

Field evaluation of effect of temperature on release of disparlure from a pheromone-baited trapping system used to monitor gypsy moth (Lepidoptera: Lymantriidae)

Traps baited with disparlure, the synthetic form of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), sex pheromone are used to detect newly founded populations and estimate population density across the United States. The lures used in trapping devices are exposed to field conditions with varying climates, which can affect the rate of disparlure release. We evaluated the release rate of disparlure from delta traps baited with disparlure string dispenser from 1 to 3 yr across a broad geographic gradient, from northern Minnesota to southern North Carolina. Traps were deployed over approximately 12 wk that coincided with the period of male moth flight and the deployment schedule of traps under gypsy moth management programs. We measured a uniform rate of release across all locations when considered over the accumulation of degree-days; however, due to differences in degree-day accumulation across locations, there were significant differences in release rates over time among locations. The initial lure load seemed to be sufficient regardless of climate, although rapid release of the pheromone in warmer climates could affect trap efficacy in late season. Daily rates of release in colder climates, such as Minnesota and northern Wisconsin, may not be optimal in detection efforts. This work highlights the importance of local temperatures when deploying pheromone-baited traps for monitoring a species across a large and climatically diverse landscape.     

Effects of pheromone plume structure and visual stimuli on the pheromone-modulated upwind flight of male gypsy moths (Lymantria dispar) in a Forest (Lepidoptera: Lymantriidae)

The pheromone-modulated upwind flight ofLymantria dispar males responding to different pheromone plume structures and visual stimuli designed to mimic trees was video recorded in a forest. Males flying upwind along pheromone plumes of similar structure generated tracks that were similar in appearance and quantitatively similar in almost all parameters measured, regardless of the experimentally manipulated visual stimuli associated with the pheromone source. Net velocities, ground speeds, and airspeeds of males flying in point-source plumes were slower than those of males flying in the wider, more diffuse plumes issuing from a cylindrical baffle. The mean track angle of males flying in plumes issuing from a point source was greater (oriented more across the wind) than that of males flying in plumes issuing from a transparent cylindrical baffle. Males flying in point-source plumes also turned more frequently and had narrower tracks overall than males responding to plumes from a cylindrical baffle. These data suggest thatL. dispar males orienting to pheromone sources (i.e., calling females) associated with visible vertical cylinders (i.e., trees) use predominantly olfactory cues to locate the source and that the structure of the pheromone plume markedly affects the flight orientation and the resultant track.     

Discrimination and production of disparlure enantiomers by the gypsy moth and the nun moth

ABSTRACT. Two odour receptor cells were physiologically identified within male antennal hair sensillae of the gypsy moth, Lymantria dispar L, and the nun moth, L. monacha L. In the gypsy moth, one cell responded to (+)-disparlure, while a neighbouring cell responded to (-)-disparlure. In the nun moth both cells responded to (+)-disparlure. The lack of sensitivity to (-)-disparlure in the nun moth was corroborated by electroantennogram (EAG) recordings, which indicated no affinity to this enantiomer. Single cell responses of male gypsy moth to different concentrations of the synthetic enantiomers of disparlure were then compared to responses elicited by hexane extracts of female glands of both species. The gypsy moth's extracts stimulated almost exclusively the receptor cell specialized for (+)-disparlure, while both cells were simultaneously stimulated by the extracts of the nun moths. From the response characteristic of the cells it is estimated that pheromone production of the nun moth is about 10% (+) and 90% (-)-disparlure, and that of the gypsy moth is almost 100% (+)-disparlure. Stimulation of the antenna of each species by female gland extracts of both species did not indicate the presence of receptors for other hexane elutable pheromone components in either species.     

Trophic influence on the development of the gypsy moth (Lepidoptera, Lymantriidae) and the forecast of its abundance

Results of a long-term investigation on the development of the Armenian population of Lymantria dispar L. are reported. A list of host plants with their comparative characteristics and data on their effect on different developmental phases of the pest (larvae, pupae, adults, and embryos) are given. Biochemical changes in the leaves of host plants are shown to play a significant role in regulation of the L. dispar population density. Population growth can be expected when population develops on primary hosts with sufficient content of nutrients in the leaves and a certain carbohydrate to protein ratio, as well as a certain ratio of water-and alkali-soluble protein fractions. Intense weakening of the plants caused by the larval feeding affects the food value of the leaves and, subsequently, the pest metabolism, negatively affecting its general physiological condition and fecundity, which eventually results in decline of the pest population.     

Long-distance dispersal of the gypsy moth (Lepidoptera: Lymantriidae) facilitated its initial invasion of Wisconsin

Gypsy moth (Lymantria dispar L.) spread is dominated by stratified dispersal, and, although spread rates are variable in space and time, the gypsy moth has invaded Wisconsin at a consistently higher rate than in other regions. Allee effects, which act on low-density populations ahead of the moving population that contribute to gypsy moth spread, have also been observed to be consistently weaker in Wisconsin. Because a major cause of an Allee effect in the gypsy moth is mate-finding failure at low densities, supplementing low-density populations with immigrants that arrive through dispersal may facilitate establishment and consequent spread. We used local indicator of spatial autocorrelation methods to examine space-time gypsy moth monitoring data from 1996 to 2006 and identify isolated, low-density colonies that arrived through dispersal. We measured the distance of these colonies from the moving population front to show that long-distance dispersal was markedly present in earlier years when Wisconsin was still mainly uninfested. Recently, however, immigrants arriving through long-distance dispersal may no longer be detected because instead of invading uninfested areas, they are now supplementing high-density colonies. In contrast, we observed no temporal pattern in the distance between low-density colonies and the population front in West Virginia and Virginia. We submit that long-distance dispersal, perhaps facilitated through meteorological mechanisms, played an important role in the spread dynamics of the initial Wisconsin gypsy moth invasion, but it currently plays a lesser role because the portion of Wisconsin most susceptible to long-distance immigrants from alternate sources is now heavily infested.     

Iridoid glycosides and insect feeding preferences: gypsy moths (Lymantria dispar, Lymantriidae) and buckeyes (Junonia coenia, Nymphalidae)

Abstract. 1. The effect of increasing concentrations of an iridoid glycoside, catalposide, was tested on a generalist and an adapted specialist lepidopteran, using artificial diets.
2. Two strains of the gypsy moth, Lymantria dispar (L.) (Lymantriidae), were tested. Larvae of a wild strain showed a negative dose-dependent response to increasing concentrations of catalposide (up to 7.2% dry weight), while a laboratory strain showed no such pattern. Choice tests using the laboratory strain showed that these larvae often preferred diets relatively low in catalposide over those with higher concentrations.
3. In contrast, larvae of the iridoid glycoside specialist, the buckeye, Junonia coenia Hübner (Nymphalidae), showed a positive dose-dependent response and grew better on diets with higher doses of catalposide.
4. We tested whether the improved growth of J. coenia at higher concentrations of catalposide may have been due to extra glucose yielded by hydrolysis of catalposide. Larvae were fed increasing doses of glucose equivalent to the amount potentially obtained by hydrolysing the quantities of catalposide used in the previous experiment. However, added glucose did not effect growth, suggesting that increased growth at higher catalposide concentrations was due to increased feeding rates.     

Changes in range boundaries of the gypsy moth and the nun moth (Lymantria dispar,L. monacha,Lymantriidae, Lepidoptera) due to the global warming: a model approach

Entomological Review - Modeling of the gypsy moth and nun moth ranges using climatic predictors and the updated climate database suggested potential consequences of the observed climate changes for...     

The cost of slowing the spread of the gypsy moth (Lepidoptera: Lymantriidae)

Beginning in 1992, the Slow The Spread (STS) pilot project was initiated to target gypsy moth (Lymantria dispar L.) spread rate reduction by controlling populations in the transition zone. The project uses intensive monitoring techniques, with pheromone-baited sticky moth traps, to detect low-level populations and target them for eradication. The primary objective of the pilot project was to evaluate the feasibility of using integrated pest management techniques to slow the spread of gypsy moths over a large geographical area. In this study, the cost of STS pilot project activities in 1993-1995 was investigated. A cost accounting system was developed and used as a framework to collect the cost data and to investigate cost patterns and characteristics. Total expenditures of STS activities for 1993-1995 were 7,685.2 million dollars. Per unit cost was 49.67 dollars per trap with the direct cost component being 35.03 dollars per trap. Trapper labor and vehicle expense accounted for approximately 90% of this direct cost. Per unit cost for treatment activities was found to average 27.86 dollars per treated acre. In general, the STS pilot project is labor intensive, specifically the trapping component. From 1993-1995, 59% of total project expenditures were spent on trapping activities, 28% on pesticide treatments, and 13% on data management. A trapper productivity rate regression model is described.     

Foreleg stridulation in male Urania moths (Lepidoptera: Uraniidae)

Males of the uraniid moth genus Urania possess a stridulatory organ on the prothoracic leg. This organ represents an autapomorphy for the genus. The sound-producing mechanism consists of a peg formed of specialized scales on the coxa which produces a train of high pitched clicks when scraped against scales on the proximal end of the femur. The proximal end of the femur is enlarged compared with that of the females and would serve to amplify the sound pulse. Stridulation occurs during a series of rapid forward jerks of the forelegs. The sound produced by Urania consists of a low amplitude pulse audible to humans at short range but with a strong ultrasound component. It has not yet been observed in the wild and its function in these moths is unknown, but it may be used during intrasexual or perhaps intersexual communication. This organ is unlikely to have been evolved originally as a defence against nocturnal predators since the genus is a member of an exclusively diurnal clade and females lack the organ. Stridulation occurs in conjunction with fanning-out of the foreleg femoral hair pencil and this invites speculation as to a route for evolution of the organ.     

Parasitoid complex of the Asian gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) in Primorye Territory,Russian Far East

A study of the moth parasitoid complex attacking gypsy moth, Lymantria dispar (L.) was carried out in Primorye territory, Russia Far East. Season-long collections at three sites in the Vladivostok area and collections at seven sites of central region of Primorye revealed the 18 primary parasites: one egg parasitoid, 11 larval parasitoids, one larval-pupal parasitoid, one parasitic nematode, one ectoparasitoid, and three diseases including NPV (nuclear polyhedrosis virus) and Entomophaga maimaiga. Phobocampe species (Ichneumonidae) dominated the parasitoid complex, parasitizing 5.5% of the larvae in the Vladivostok area and 9.3% in central Primorye, rates which are much higher than those detected from other Asiatic regions of Russia and Northeastern Asia. The insect parasitoid complex was found to be somewhat depauperate. The 11.8% average total parasitism in eastern Russian is similar to the 12% recorded in the US. Both regions have large gypsy moth outbreaks, but other factors including diseases have compensated for the rather low mortality exerted by the parasitoid complex in the Russian Far East.     

The effects of cations on the activity of the gypsy moth (Lepidoptera: Lymantriidae) nuclear polyhedrosis virus

Fourteen cations were tested at a 1% concentration (wt:wt), as chlorides, for their effects on the biological activity of the gypsy moth, Lymantria dispar (L.), nuclear polyhedrosis virus (LdMNPV). Cupric chloride was toxic to gypsy moth larvae. Ferrous and ferric chloride were inhibitory to larval growth and development as well as to virus activity. Strontium chloride was inhibitory to virus activity but had no apparent effects on gypsy moth larvae. Six cations had little or no effect on virus activity (i.e., calcium, lanthanum, magnesium, nickel, potassium, sodium), whereas four cations (i.e., cobalt, manganese, ruthenium, zinc) acted as viral enhancers, as indicated by reductions in LC50s.     

Response of the gypsy moth Lymantria dispar L. (Lepidoptera, Lymantriidae) to the content of allelochemicals in birch leaves (Betula pendula Roth)

Structural and functional characteristics of the gypsy moth population in a birch forest were found to be correlated with the level of defoliation and the content of allelochemicals in the foliage. One year after defoliation, the content of flavonoids, total lipid fractions, fatty alcohols, and alcohols increased in the foliage of the heavily (by 75%) damaged trees, whereas the content of free sterols and triterpenes decreased. These changes were associated with low vitality of the insects and a sharp drop in the population density.     

Starvation resistance of gypsy moth,Lymantria dispar (L.) (Lepidoptera: Lymantriidae): tradeoffs among growth,body size,and survival

Summary Survival and body composition of starving gypsy moth larvae initially reared on aspen foliage or artificial diet differeing in nitrogen (N) and carbohydrate concentration were examined under laboratory conditions. Diet nitrogen concentration strongly affected starvation resistance and body composition, but diet carbohydrate content had no effects on these. Within any single diet treatment, greater body mass afforded greater resistance to starvation. However, starving larvae reared on 1.5% N diet survived nearly three days longer than larvae reared on 3.5% N diet. Larvae reared on artificial diet survived longer than larvae reared on aspen. Differences in survival of larvae reared on artificial diet with low and high nitrogen concentrations could not be attributed to variation in respiration rates, but were associated with differences in body composition. Although percentage lipid in larvae was unaffected by diet nitrogen concentration, larvae reared on 1.5% N diet had a higher percentage carbohydrate and lower percentage protein in their bodies prior to starvation than larvae reared on 3.5% N diet. Hence, larger energy reserves of larvae reared on low nitrogen diet may have contributed to their greater starvation resistance. Whereas survival under food stress was lower for larvae reared on high N diets, growth rates and pupal weights were higher, suggesting a tradeoff between rapid growth and survival. Larger body size does not necessarily reflect larger energy reserves, and, in fact, larger body size accured via greater protein accumulation may be at the expense of energy reserves. Large, fast-growing larvae may be more fit when food is abundant, but this advantage may be severely diminished under food stress. The potential ecological and evolutionary implications of a growth/survival tradeoff are discussed.     

Increased mortality of gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae) exposed to gypsy moth nuclear polyhedrosis virus in combination with the phenolic gycoside salicin

Second instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), larvae suffered significantly greater mortality from aerially applied gypsy moth nuclear polyhedrosis virus (Gypchek) when the virus was consumed on quaking aspen, Populus tremuloides Michx., versus red oak, Quercus spp. L., foliage. Laboratory assays in which various doses of Gypchek and salicin (a phenolic glycoside present in aspen foliage) were tested in combination demonstrated that salicin significantly increased total larval mortality and lowered the LD50 estimates (dose of Gypchek that resulted in 50% population mortality) for the virus, although not significantly. While salicin did not impact larval survival in the absence of Gypcek, it did act to significantly deter feeding when it was present in high concentrations (up to 5.0%) within the treatment formulations. The enhanced activity of Gypchek in the presence of salicin is similar to prior reports of enhanced activity of the bacterial pathogen Bacillus thuringiensis when consumed concurrently with phenolic glycosides commonly present in aspen foliage. The enhancement of viral activity is in contrast to the inhibitory effects on the virus reported for another common group of phenolic compounds, tannins.     

Pheromone-mediated upwind flight of male gypsy moths, Lymantria dispar, in a forest

Abstract Lymantria dispar L. males flying upwind in a pheromone plume in a forest were video-recorded at 2.5, 10 and 20 m from the source of pheromone. Males flew slower and steered more across the wind as they approached the source. In concert, their ground speed decreased and track angles increased. In contrast to these changes, their drift angles were fairly constant and the transverse component of image flow, above and/or below the moths eyes, showed almost no change. The inter-turn duration (time between sequential turns), a temporal aspect of the male flight manoeuvres, showed a consistent but relatively small increase as the distance from the source increased. The flight tracks narrowed as the males approached close (2.5 m) to the source. Because of unpredicted correlations between physical variables (i.e. temperature, wind velocity) and the distance from the source, we used principal components analysis to generate a set of completely independent variables. Greater than 90% of the variability in the data could be explained by four principal factors which corresponded well with known relationships in the flight manoeuvres. All four of these factors showed a significant regression against distance to the source. Although uncontrolled factors such as temperature and wind velocity may have contributed to changes in flight behaviour, recent data indicate that, in addition to concentration, certain temporal and spatial characteristics (i.e. burst period, burst return period) of plumes in wind vary systematically with distance from the source. We propose that L.dispar males might adjust their flight manoeuvres in response to these changes.     

Evaluation of a nonconventional insecticide and appropriate application timing for destruction of gypsy moth (Lepidoptera: Lymantriidae) egg masses

Two field studies were conducted in 2001-2002 and 2003 to evaluate the effectiveness and appropriate application timing of Golden Pest Spray Oil (GPSO) for destruction of gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), egg masses in Wisconsin. GPSO is a commercially available, registered pesticide that is predominantly comprised of a soybean-oil base (93%); its primary mode of action is by means of suffocation. Because gypsy moth spends the majority (>75%) of its life cycle in the egg stage (August-April), the potential utility of this product by arborists, city foresters, landscapers, and homeowners is high, especially because GPSO is a United States Environmental Protection Agency registered, nonconventional pesticide that is considered relatively nontoxic. When GPSO was applied at a 1:1 ratio with water, >96% control of gypsy moth egg masses was achieved, regardless of application timing (October, 3 d before egg hatch).     

Effect of two granulosis viruses on the activity of the gypsy moth (Lepidoptera: Lymantriidae) nuclear polyhedrosis virus

Two granulosis viruses (GV) were tested as enhancers for the gypsy moth nuclear polyhedrosis virus (LdMNPV). Helicoverpa armigera (Hübner) CV (HaGV) had no detrimental effect upon larval growth and development, but in combination with LdMNPV it reduced both the LC50 and the LT50 for the NPV. In addition, the combination also adversely affected the growth and development of gypsy moth larvae. The LC50 of LdMNPV was reduced by as much as 300-fold (HaGV at 10(-2) dilution) and the LT50 was reduced by as much as 18% (HaGV at 10(-2) dilution). Spodoptera frugiperda (J. E. Smith) GV reduced the LC50 of LdMNPV by as much as 13-fold but had no effect upon the LT50.