The history and control of the pine beauty moth, Panolis flammea (D. & S.) (Lepidoptera: Noctuidae), in Scotland from 1976 to 2000

1 The pine beauty moth, Panolis flammea, has been a serious pest of lodgepole pine plantations in Scotland since 1976. It historically feeds on native Scots pine throughout Europe but population levels of P. flammea on this host have never been high enough to cause tree mortality in the U.K. 2 This paper reviews recent advances in the biology of the pest and documents control programmes from 1976 to 1999. 3 There has been practically uninterrupted population monitoring of P. flammea from 1977 to the present day in Scottish lodgepole pine plantations. Intervention with chemical spraying has often been necessary. 4 The population data suggest that populations of P. flammea may have had a cyclic pattern over the monitoring period, with outbreaks occurring at regular intervals of between 6 and 7 years. 5 The amplitude of population cycles was large during the 1970s and 1980s, but has dampened in recent years. Natural enemies are believed to contribute to this trend. Fungal disease, specifically, appears to have had a greater effect on pest populations in recent years than in the past and is suggested to have contributed significantly to the population dynamics observed since 1990.     

The chemical composition of pine foliage in relation to the population dynamics of the pine beauty moth,Panolis flammea,in Scotland

Summary This paper reports part of a study to determine why damaging outbreaks of the pine beauty moth, Panolis flammea (D & S) (Lepidoptera: Noctuidae), in Scotland are frequent on lodgepole pine but do not occur on Scots pine, and why outbreaks on lodgepole pine are mainly confined to trees growing in deep unflushed peat. The elongation of shoots and the growth of needles of Scots pine occurred later in the season than did those of lodgepole pine. The foliage of Scots pine generally had a higher level of nitrogen, and consistently had a higher level of phosporus, but had a consistently lower level of tannins than that of lodgepole pine during the period when the larvae were feeding each year. The nitrogen content of the foliage of lodgepole pine growing in an iron pan soil was generally higher than that of lodgepole pine growing in deep peat during the same period but there were no general differences in the phosphorus or tannin contents of lodgepole pine in the 2 soil types. These findings suggest that Scots pine is a more suitable host plant than lodgepole pine and that the foliage of lodgepole pine growing in deep peat is not more suitable than lodgepole pine growing in an iron pan soil. On the basis of the chemical analyses used in this study, it is concluded that the abundance of pine beauty moth in Scotland is not strongly influenced by the nutritional suitability of its host plants.     

MaleHeliothis virescens maintain upwind flight in response to experimentally pulsed filaments of their sex pheromone (Lepidoptera: Noctuidae)

Aspects of the intermittent fine structure of an odor plume were mimicked and experimentally modified in the wind tunnel using an air-pulsing device. Filaments of a behaviorally active blend of six sex-pheromone components created by the device in a temporally regular fashion elicited sustained upwind flight and source location in male Heliothis virescens.Males did not exhibit sustained upwind flight in significant numbers until a frequency of 4 filaments/s was delivered, at a loading of 1 g of the major component, Z11-16: Ald, with the other components loaded at their appropriate ratios. A loading of 10 g Z11-16: Ald was found to be optimal at this filament delivery rate. Electroantennogram recordings to different filament delivery rates of the complete blend indicated that a stationary male antenna can respond to the pulse rates used in this study. Importantly, when a main component necessary for upwind flight, Z9-14:Ald, was isolated into its own filaments and pulsed alternately against filaments of the five other components (including the other component essential for upwind flight, Z11-16: Ald), upwind flight to the source was significantly reduced (9%) compared to upwind flight and source location in response to filaments composed of the entire blend (30%), indicating that the complete pheromone blend must arrive on the antenna simultaneously for optimal evocation of sustained upwind progress. Neurophysiological evidence from other studies suggests that higher-order interneurons whose phasic response is enhanced when the entire blend is presented simultaneously may be of importance in explaining this behavioral difference stemming from synchronous vsasynchronous arrival of the components.     

The significance of Cognettia sphagnetorum(Enchytraeidae) on nitrogen availability and plant growth in wood ash-treated humus soil

A laboratory microcosm experiment was established to study whether the role of Cognettia sphagnetorum (Enchytraeidae) in affecting Scots pine (Pinus sylvestris) seedling growth is influenced by wood ash-amendment, i.e., neutralisation of the raw humus soil. Coniferous forest soil, inoculated with soil microbes and nematodes, was either treated with wood ash or left as ash-free control. Wood ash (corresponding to an amount of 5000 kg ha^–1) was either spread on the soil surface or mixed into the soil. Enchytraeid and pine seedling biomass, abundance of nematodes, and water leachable NH₄ ⁺-N and NO₃ ^–-N were measured 26 and 51 weeks after initiation of the experiment and root length and N concentration of needles were measured 51 weeks after initiation of the experiment. Wood ash when mixed into the soil, reduced the biomass of C. sphagnetorum. Nematodes were unaffected by the treatments. In the ash-free soils C. sphagnetorum had little influence on pine growth, but it did decrease root length and root to shoot ratio. In the absence of enchytraeids wood ash decreased pine biomass production and root length. However, the presence of enchytraeids in the ash-treated soil compensated the ash-induced negative effects on the pine performance. Enchytraeids increased and wood ash decreased water leachable NH₄ ⁺-N in the presence but not in the absence of enchytraeids, while water leachable NO₃ ^–-N was not affected by the treatments. It was concluded that C. sphagnetorum can be important in ensuring nutrient cycling and plant growth in situations when an ecosystem encounters disturbances.     

Competition alters plant species response to nickel and zinc

Phytoextraction can be a cost-efficient method for the remediation of contaminated soils. Using species mixtures instead of monocultures might improve this procedure. In a species mixture, an effect of heavy metals on the species' performance can be modified by the presence of a co-occuring species. We hypothesised that (a) a co-occuring species can change the effect of heavy metals on a target species, and (b) heavy metal application may modifiy the competitive behaviour between the plants. We investigated these mechanisms in a greenhouse experiment using three species to serve as a model system (Carex flava, Centaurea angustifolia and Salix caprea). The species were established in pots of monocultures and mixtures, which were exposed to increasing concentrations of Ni and Zn, ranging from 0 to 2,500 mg/kg. Increased heavy metal application reduced the species' relative growth rate (RGR); the RGR reduction being generally correlated with Ni and Zn concentrations in plant tissue. S. caprea was an exception in that it showed considerable Zn uptake but only moderate growth reduction. In two out of six cases, competitors significantly modified the influence of heavy metals on a target species. The interaction can be explained by an increased uptake of Zn by one species (in this case S. caprea) that reduced the negative heavy metal effect on a target species (C. flava). In two further cases, increasing heavy metal application also altered competitive effects between the species. The mechanisms demonstrated in this experiment could be of relevance for the phytoextraction of heavy metals. The total uptake of metals might be maximised in specific mixtures, making phytoextraction more efficient.     

The effect of previous defoliation of pole-stage lodgepole pine on plant chemistry,and on the growth and survival of pine beauty moth (Panolis flammea) larvae

Summary A study of the effects of defoliation by insects on the chemistry of lodgepole pine (Pinus contorta), and on the performance of Panolis flammea (Lepidoptera; Noctuidae) larvae, was carried out in a forest in northwest Scotland I year after a severe outbreak of P. flammea had caused extensive defoliation. Larval weight and survival were not significantly different on trees that had experienced different levels of defoliation in 1986. The nitrogen and tannin content of current and previous years' pine needles was not significantly affected by defoliation (although both were slightly greater in the foliage of defoliated trees). Phosphorus content of young pine foliage was lower (but not significantly lower except on one occasion) on heavily defoliated trees. On all sampling occasions, however, the nitrogen: phosphorus ratio was significantly higher on heavily defoliated trees. There were large differences in monoterpene composition of the previous year's shoots associated with defoliation intensity, but these differences had largely disappeared in the new growth. The results are discussed in relation to other studies on the effects of insect damage on plant chemistry and insect performance and in relation to the abundance of P. flammea in Scotland.     

Adaptive significance of egg size plasticity in response to temperature in the migrant skipper, Parnara guttata guttata (Lepidoptera: Hesperiidae)

Females of the migrant skipper, Parnara guttata guttata, that are reared under lower temperatures lay smaller eggs. The adaptive significance of egg size plasticity in response to temperature is unknown in this species. We suggest, based on the following experimental results, that P. g. guttata uses temperature as an indirect cue to predict the host condition (leaf toughness) of the next generation. First, larvae were reared under the typical conditions of temperature and photoperiod experienced during the immature stages in the first, second, and overwintering (third) generations (LD 16:8 at 25°C, LD 14:10 at 25°C and LD 14:10 at 20°C). Females reared under LD14:10 at 20°C produced more, smaller eggs than those reared under LD14:10 and LD16:8 at 25°C. Secondly, survival rates of first instar larvae derived from females reared under the three photoperiod/temperature treatments were measured on young soft rice leaves (soft), or tough, old rice leaves (tough). Survival rates of hatchlings reared on soft and tough leaves did not differ when females were reared under LD16:8 and LD14:10 at 25°C. However, hatchling survival was significantly higher on soft than on tough leaves when females were reared under LD14:10 at 20°C. Thirdly, we found that egg size plasticity in response to temperature in P. g. guttata may be a threshold response. Temperatures below 20°C experienced during the immature stages may be effective for production of smaller and more eggs in the overwintering generation of P. g. guttata.     

The effect of neonatal starvation on the growth,development and survival of larvae of the pine beauty moth,Panolis flammea (D & S)

Summary Mortality of neonatal pine beauty moth larvae varied from 0% to 100% depending on the duration of food deprivation and temperature. At 20°C and 100% RH all larvae had died by the fourth day of food deprivation, whereas at 10°C and 100% RH larvae survived for twelve days without food. Although larvae were able to survive at 15°C for up to seven days without food, establishment on thier host at this temperature was seriously affected by three days of starvation. No establishment took place after four days of starvation at 15°C. At 10°C establishment was significantly affected by starvation but not to such a marked degree. Establishment at both 15°C and 10°C was enhanced if the larvae were presented with a highly suitable host. The mean relative growth rate of those larvae reaching fifth instar was unaffected by the duration of their prefeeding starvation period. However, overall mean relative growth rates of the larvae were significantly affected by the duration of the starvation period. The implications of these results are discussed in relation to the population dynamics of this insect.     

Seasonal changes in plasma membrane H<Superscript>+</Superscript>-ATPase activity of <Emphasis Type="Italic">Vaccinium myrtillus</Emphasis> (L.) and <Emphasis Type="Italic">Pinus sylvestris</Emphasis> (L.)

Seasonal changes in vanadate sensitive plasma membrane H⁺-ATPase activity of bilberry (Vaccinium myrtillus L.) and Scots pine (Pinus sylvestris L.) were studied in a period from February to August in northern Finland. The plasma membrane isolation was performed by sucrose gradient centrifugation, and the H⁺-ATPase activity was assayed by spectrophotometrical determination of released inorganic phosphate. The studied species showed seasonal changes from high winter to low spring activity, indicating probable physiological changes between hardened and dehardened tissue. ATPase activity of bilberry peaked up at the beginning of the growth period, obviously due to active phloem loading of photosynthates.     

Contribution to the taxonomy of Pinus uncinata (Pinaceae) based on cone characters

Eight natural populations of Pinus uncinata Ramond from the Spanish Pyrenees, five of P. mugo Turra from the Carpathians, the Sudethians and Abruzzian Apennines, three of P. sylvestris L. from the Central-European Lowland and the Iberian Peninsula and one of P. uliginosa Neumann from SW Poland have been compared biometrically in 16 cone characters. P. uncinata appears the most distant from all other taxa, differing by having the largest and most asymmetric cones and the thickest apophyses with the most prominent umbo. In cone characters, P. mugo is more similar to P. sylvestris than to P. uncinata. Nevertheless, P. mugo and P. sylvestris remain distant from each other in a number of morphological characters examined. P. uliginosa has cones intermediate between the other three taxa and is moreover very variable. The locality of P. uliginosa in the Silesian Lowland may be of a relict character and conserve genes from P. uncinata.     

The action of acephate in Pseudoplusia includens (Lepidoptera: Noctuidae) and Pristhesancus papuensis (Hemiptera: Reduviidae)

The toxicity, toxodynamics, and toxokinetics of acephate were investigated in the soybean looper, Pseudoplusia includens, and a predatory reduviid, Pristhesancus papuensis. Acephate was nine-fold more toxic to the predator than the phytophagous soybean looper at the LD₅₀. Both acephate and its presumed activation product, methamidophos, were found to be inhibitors of acetylcholinesterase (AcChE) in vitro. Acetylcholinesterase from P. includens was more susceptible to inhibition by both chemicals than was P. papuensis AcChE. The overall rate of penetration, metabolism, and excretion was more rapid in P. includens than in the predator. The activation of acephate to methamidophos was four times greater in P. papuensis than in P. includens after a 24-h exposure period. No labeled CO₂ was detected from P. papuensis, while over 5% of the applied dose was trapped as CO₂ from P. includens. The activation and accumulation steps then, are apparently the major reasons for the greater toxicity of acephate to P. papuensis compared to P. includens.

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Résumé L'action de l'acéphate (orthène) a été déterminée sur une lignée de Pseudoplusia includens et un prédateur éventuel, Pristhesancus papuensis. Appliqué localement, l'acéphate a été très toxique pour les 2 espèces, bien que le prédateur ait été 9 fois plus sensible que la noctuelle à la DL50.Tant l'acéphate qu'un composé similaire, le méthamidophos, ont inhibé l'acétylcholinestérase (AcChE) in vitro. Le pouvoir inhibiteur du méthamidophos était, cependant, 1 000 fois plus puissant que celui de l'acéphate sur cette enzyme. L'enzyme de P. includens a été plus susceptible d'inhibition par ces 2 substances que l'AcChE de P. papuensis.La pénétration de la radioactivité à la suite d'un traitement au ¹⁴C-acéphate a été rapide chez P. includens, chez lequel au bout de 48 h il y avait eu accumulation interne de 43% de la dose appliquée. La pénétration de l'acéphate chez P. papuensis a été moins rapide, n'atteignant que 21% au bout de 48 h. Le taux de CO₂ marqué dégagé 24 h après le traitement a été déterminé en utilisant un collecteur de CO₂ respiratoire et un piège. Aucun CO₂ marqué n'a été décelé à partir du prédateur, tandis que plus de 5% de la dose appliquée a été piégée sous forme de CO₂ chez la noctuelle. P. papuensis a activé in vivo 4 fois la proportion d'acéphate appliqué par rapport au méthamidophos que ne l'a fait P. includens; cependant aucun d'eux n'a été éliminé dans les fécès. D'autre part, chez P. includens, le méthamidophos et l'acéphate non métabolisé ont été perdus dans le bocal d'élevage, et seulement la moitié du taux de radioactivité interne était présent au bout de 24 h. Les étapes de l'activation et de l'accumulation ont été les principales raisons de la plus grande toxicité de l'acéphate pour le prédateur.

     

Susceptibility of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) to Vip3A insecticidal protein expressed in VipCot™ cotton

Susceptibility of laboratory and field colonies of Helicoverpa zea (Boddie) and Heliothis virescens F. to Vip3A insecticidal protein was studied in diet incorporation and diet overlay assays from 2004 to 2008. Responses of field populations were compared to paired responses of University of Arkansas laboratory susceptible H. zea (LabZA) and H. virescens (LabVR) colonies. After 7 d of exposure, observations were made on number of dead larvae (M) and the number of larvae alive but remaining as first instars (L1). Regression estimates using M (LC₅₀) and M plus L1 (MIC₅₀) data were developed for laboratory and field populations. Susceptibility of laboratory and field populations exposed to Vip3A varied among different batches of protein used over the study period. Within the same batch of Vip3A protein, susceptibilities of laboratory colonies of both species (LabZA and LabVR) were similar. Field colonies were significantly more susceptible to Vip3A than the respective reference colonies of both species. Within field populations, susceptibility to Vip3A varied up to 75-fold in H. zea and 132-fold in H. virescens in LC₅₀ estimates. Variabilities in MIC₅₀s were up to 59- and 11-fold for H. zea and H. virescens, respectively.     

Abortive embryogenesis in hybrid swarm populations of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. and <Emphasis Type="Italic">Pinus muga</Emphasis> Turra

Comparative study on fertilization process in Pinus sylvestris, Pinus mugo and in their putative hybrid swarm individuals was done involving pre-zygotic and post-zygotic stages. The amount of surviving ovules from open pollination reflecting the mode of interaction between pollen grains and nucellar tissue of an ovule averaged at 8.1 of sound ovules per conelet in Pinus sylvestris, 7.3 ovules in the hybrid swarm population and at 4.9 ovules in Pinus mugo. A strong correlation was observed between the number of surviving ovules and the proportion of germinating seeds in the compared species and hybrids. Normal course of embryogenesis in Pinus sylvestris and Pinus mugo contrasted with increased frequency of disturbances observed in the hybrid swarm individuals. The differential survival rates of the ovules and deviations from typical pattern of embryogenesis are discussed from the standpoint of cross-ability relationship between Pinus sylvestris and Pinus mugo.     

Occurrence of carpophores of ectomycorrhizal fungi in selected stands ofPinus sylvestris in the Netherlands in relation to stand vitality and air pollution

The relation between the occurrence of carpophores of mycorrhizal fungi, tree vitality, and air pollution in ‘young’ (5–10 years) and ‘old’ (50–80 years) stands ofPinus sylvestris L. was investigated. In the Netherlands 21 homogeneous plots of 1000 m² were selected on dry, sandy soils. Tree vitality was assessed in the summer of 1985 and during the autumn the plots were searched for carpophores of mycorrhizal fungi. In the young plots 3 times more species of ectomycorrhizal fungi and 20 times more carpophores per plot were found than in the old plots. In the old plots, the number of carpophores and the number of species showed significant positive correlations with the average number of needleyears of the trees. The number of carpophores and the number of species were significantly negative correlated with the concentrations of SO₂ and O₃ in the air and the amount of NH₃ emission. The number of needleyears, the crown density and the overall tree vitality were found to be significantly negative correlated with the amount of NH₃ emission, and the number of needleyears also with the concentration of O₃ in the air. Such correlations were not found for the young plots. No differences were found in soil chemical properties between the plots. Evidence was obtained that the fructification of mycorrhizal fungi of old stands ofPinus sylvestris is influenced by air pollution either directly, or indirectly by way of tree vitality. It is hypothesized that the young plots offer more advantageous circumstances for fructification of the fungi because of the disturbance of the upper soil-layer at the time of planting.     

Microscopic structure of Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> (L.)) needles during ageing and autumnal senescence

Needle ageing and senescence were studied in Scots pine (Pinus sylvestris) trees growing in natural conditions with minimal anthropogenic influence. The four existing needle generations were analyzed by light and transmission electron microscopy before and during autumnal yellowing of the oldest needle generation. The change from green to yellow occurred within less than 4 days in central Finland. The structure of the oldest needles remained largely intact as long as they were green. Increase in mitochondrion size and hypertrophy of the phloem parenchyma were the only changes, probably related to the approaching senescence. In the yellow needles, the structure of the mesophyll tissue varied from nearly intact with reduced chloroplasts and higher numbers of plastoglobuli, to totally disintegrated cells. In the disintegrated cells, peroxisomes were absent, and chloroplasts were smaller with a patchy appearance and degraded, eventually empty-looking stroma. Mitochondria were enlarged, but retained integrity until the last stages of deterioration, and lipids increased. At the light microscopic level, vacuolar volume in mesophyll cells and cavity formation in transfusion tissue increased. Ageing was characterized by increases in the vacuolar volume and cytoplasmic lipids, altered appearance of vacuolar tannin from homogenous ‘sandy’, to large spherical drops and finally to a large mass in the mesophyll, and by hypertrophy and tannin accumulation in the phloem parenchyma. Changes related to needle ageing, senescence and cell location in the mesophyll tissue were discussed relative to findings with stress by strong light, weather conditions and ozone.     

Behavioral and electrophysiological responses of Helicoverpa assulta, H. armigera (Lepidoptera: Noctuidae), their F1 hybrids and backcross progenies to sex pheromone component blends

Two sibling species, Helicoverpa assulta and Helicoverpa armigera both use (Z)-9-hexadecenal and (Z)-11-hexadecenal as their sex pheromone components but in almost reversed ratios, 93:7 and 3:97, respectively. H. assulta and H. armigera males performed upwind flight in response to the H. assulta sex pheromone blend (93:7). H. armigera responded strongly to the H. armigera blend (3:97), whereas H. assulta males remained inactive upon exposure to this blend. Both species gave clear dose-dependent electrophysiological responses to (Z)-11-hexadecenal. However, (Z)-9-hexadecenal evoked strong dose-dependent electrophysiological responses in H. assulta males but not in H. armigera. The two male F₁ hybrids exhibited similar behavioral responses to two sex pheromone blends and electrophysiological responses to two pheromone components as H. armigera males. This indicated that H. armigera genes appear dominant in determining the behavioral response and electrophysiological responses. Behavioral and electrophysiological responses of backcrosses of male F₁ hybrids (H. armigera female × H. assulta male) with female H. assulta and H. armigera were close to that of H. assulta and H. armigera, respectively. However, backcrosses of female F₁ hybrids (H. assulta female × H. armigera male) with male H. assulta and H. armigera showed reduced behavioral responses but normal electrophysiological responses compared to males of the respective parental line.     

Decreased Response to Feeding Deterrents Following Prolonged Exposure in the Larvae of a Generalist Herbivore, Trichoplusia ni (Lepidoptera: Noctuidae)

We investigated the role of experience with several antifeedants on the feeding behavior of a generalist herbivore, Trichoplusia ni. Second-, third-, and fifth-instar larvae of T. ni were examined for their feeding responses to plant extracts (Melia volkensii, Origanum vulgare) and individual plant allelochemicals (cymarin, digitoxin, xanthotoxin, toosendanin, and thymol), after being exposed to them continually beginning as neonates. All tested instars of T. ni were capable of showing a decreased antifeedant response following prolonged exposure to most of the antifeedants tested compared with their naive conspecifics. Cardenolides (digitoxin and cymarin) were the exceptions. The response to oregano was affected as a result of previous exposure to different concentrations of oregano, unlike M. volkensii, leading us to conclude that T. ni sensitivity varies between stimuli and cannot be generalized. To demonstrate that decreased deterrence following prolonged exposure to M. volkensii was the result of learned habituation, three aversive stimuli were used. A high concentration of the particular antifeedant, xanthotoxin, acted as a noxious stimulus and dishabituated (reversed) the decrement in the antifeedant response to M. volkensii. Cold shock or CO₂ was marginally effective in dishabituating the response. The fact that the decrease in antifeedant response can be dishabituated has implications for pest management.     

The ion concentration of dew condensed on Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) needles

Summary Dew droplets collected with pipettes from coniferous needles were analysed for their ionic composition. Almost all samples of dew taken from Scots pine trees (Pinus sylvestris) showed significantly higher ion concentrations than those taken from Norway spruce trees (Picea abies). This can be explained by the micromorphology of the needle surface. The higher microscale roughness of the wax layer of a pine needle causes a more efficient flux of atmospheric aerosol particles compared to the spruce needle surface. Dew on coniferous needles is shown to be capable of maintaining pH values below 3 for several hours.     

On the selective forces acting in the industrial melanism of Biston and Oligia moths (Lepidoptera: Geometridae and Noctuidae)

Melanic and typical morphs of Biston betularius (L.), Oligia latruncula (D. & S.) and 0. strigilis (L.) made choices between vertical trunks and horizontal branches, sprayed with white and black paints, in a transparent plastic cylinder in natural illumination. The moths settled in exposed positions. In neither Biston nor Oligia did the choice for white/black backgrounds differ between the morphs. Biston moths settle on narrow branches (not on twigs) with the body at right angles to the longitudinal axis of the branch. The Oligias showed an asymmetrical light reaction: one eye is kept in shadow so that they settle as a continuation of an irregularity of the surface, often of a lichen.
In nature, Biston betularius probably rests high up in the canopies, on the under surfaces of horizontal branches. The visual selection acting on the morphs is expected to be less intensive than that measured on tree trunks. The mark-release-recapture results of Kettlewell (1955a, 1956) do not show any qualitative change during the self-determination of the moths but the material is too limited for firm conclusions.
Newly-hatched Biston males take off straight from the trunk where they have expanded their wings but the females may climb higher in the tree. A hypothesis is presented to explain the black-and-white coloration of f. carbonaria : the short-winged moths climbing up the trunks might deter bird predation.