Effect of Long-Term Forest Fertilization on Scots Pine Xylem Quality and Wood Borer Performance

We tested whether changes in long-term nutrient availability would affect the xylem quality and characteristics of Scots pine trees as a food source for the larvae of the xylophagous wood borer Hylotrupes bajulus L. (Cerambycidae). We looked for an effect of host plant growth and xylem structural traits on H. bajulus larval performance, and looked for delayed effects of long-term forest fertilization on xylem chemical quality. In general, larval performance was dependent on larval developmental stage. However, the growth of larvae also varied with host plant quality (increases in the concentration of nitrogen and carbon-based secondary compounds of xylem were correlated with a decrease in the larval growth rate). The greater annual growth of trees reduced tracheid length and correlated positively with second-instar H. bajulus growth rate. This is consistent with the hypothesis that intrinsic growth patterns of host plants influence the development of the xylophagous wood borer H. bajulus.     

Influence of foliar glucosinolates in oilseed rape and mustard on feeding and growth of the bertha armyworm,Mamestra configurata Walker

The relationship between host plant glucosinolate profile and feeding and growth of the Bertha armyworm,Mamestra configurata Walker was investigated using eight cultivated rape and mustard varieties. Mean larval weights of neonates reared on intact rosette-stage plants were significantly different on the different species in the orderBrassica juncea <Sinapis alba <B. napus <B. campestris. WhileB. juncea was least preferred,S. alba was significantly more attractive to neonate larvae in choice tests. Relative consumption and growth rates of fourth-instar larvae were also reduced onB. juncea foliage. Other differences were dependent on the plant growth stage. Neonate preference was not correlated to total glucosinolate levels, but rather to the concentrations of isothiocyanate-releasing glucosinolates. However, the relationship between consumption and glucosinolate levels was inconsistent. Relative growth rate was negatively correlated to total glucosinolate content for stage 3 and 4 foliage—mainly due to the concentration of isothiocyanatereleasing glucosinolates. The relative importance of isothiocyanate-releasing glucosinolates was verified by rearing neonates on meridic diets containing equimolar concentrations of sinigrin, its metabolite, allyl isothiocyanate, and indole-3-carbinol, metabolite of 3-indolylmethyl glucosinolate. Sinigrin and allyl isothiocyanate in the diet produced virtually identical negative weight vs. concentration regression lines. No such dose-response effect was observed with indole-3-carbinol. The data suggest that foliar isothiocyanate-releasing glucosinolates may provide some degree of plant protection from polyphagous insects.     

Host preference ofPissodes strobi peck (Coleoptera: Curculionidae) reared from three native hosts

In forced feeding bioassays,Pissodes strobi reared from eastern white pine, Engelmann spruce, or Sitka spruce failed to discriminate between these three host species. However, results of choice feeding bioassays suggest that eastern white pine is the ancestral host of the two westernP. strobi populations. Comparative feeding data obtained under conditions of choice support the hypothesis thatP. strobi has dispersed westward across the North American continent, adapting its host selection behavior in turn to Engelmann spruce and then Sitka spruce. WhereasP. strobi reared from eastern white pine preferred to feed on its natural host rather than on the two western spruces,P. strobi reared from Engelmann spruce did not discriminate between eastern white pine and its natural host, Engelmann spruce, but fed significantly more on these two hosts than on Sitka spruce.P. strobi reared from Sitka spruce, on the other hand, fed equally on all three native host species. Our data support the contention of Smith and Sugden (1969) that the two western weevils are eco types ofP. strobi. Comprehensive research on behavioral adaptations to new host species may allow the threeP. strobi populations to be distinguished as legitimate ethospecies.Research supported by Canadian Forestry Service Science Subvention Grant, National Science Foundation (USA) Grant No. B MS-7413 643, and National Research Council (Canada) Grant No. A3881.     

Effect of experience with pine (Pituophis melanoleucus) and king (Lampropeltis getulus) snake odors on Y-maze behavior of pine snake hatchlings

The abilities of hatchling pine snakes (Pituophis melanoleucus) and king snakes (Lampropeltis getulus) to discriminate the chemical trails of pine and king snakes was investigated inY-maze experiments. Pine snakes were housed for 17 days either with shavings impregnated with pine snake odor, king snake odor, or no odor to test for the effect of experience on choice. Both pine and king snake hatchlings entered the arm with the pine snake odor and did not enter the arm with the king snake odor. The data support the hypothesis that hatchlings of both species can distinguish conspecific odors from other odors and that our manipulation of previous experience was without effect for pine snake hatchlings.     

Accumulation of Glucosinolates by the Cabbage Aphid Brevicoryne brassicae as a Defense Against Two Coccinellid Species

Brassica nigra plants, characterized by high levels of sinigrin, and artificial aphid diets to which sinigrin was selectively added were used to rear the crucifer specialist, Brevicoryne brassicae. Aphids were provided as a food source to two species of polyphagous ladybird, Adalia bipunctata and Coccinella septempunctata. First instar A. bipunctata were unable to survive when fed with B. brassicae reared on B. nigra or diets containing 0.2% sinigrin, but when fed with aphids reared on diets containing 0% sinigrin, survival rates were high. By contrast, first instar C. septempunctata were able to survive when fed with aphids reared on B. nigra or artificial diets containing up to 1% sinigrin. However, the presence of sinigrin in the aphid diet decreased larval growth and increased the time necessary for larvae to reach second instar for this species of ladybird. These results indicate that the presence of sinigrin in the diet of B. brassicae makes this aphid unsuitable as a food source for A. bipunctata but not for C. septempunctata, although for this ladybird species, there appear to be costs associated with feeding on aphids that contain this secondary metabolite.     

Role of cucurbitacin C in resistance to spider mite (Tetranychus urticae) in cucumber (Cucumis sativus L.)

Cucurbitacins are bitter triterpenoid compounds that are toxic to most organisms and occur widely in wild and cultivated Cucurbitaceae. The only cucurbitacin identified in Cucumis sativus is cucurbitacin C. The bitter taste of cucumber has been correlated with resistance to the spider mite Tetranychus urticae, but a quantitative relationship has not been established. We determined the spider mite resistance and cucurbitacin C content in the dihaploid progeny derived from the F₁ generation of a cross between a bitter, spider-mite-resistant cucumber line and a bitter-free, spider-mite-susceptible line. The ratio of the number of bitter to bitter-free dihaploids conformed to the expected 1:1 ratio, based on a monogenic segregation pattern. Genetic analysis ascribed 69% of the variance of the difference in spider mite survival rate to the bitterness locus. Within the group of bitter dihaploids, cucurbitacin C content was significantly correlated with spider mite resistance. Thus, a quantitative relationship between cucurbitacin C content and spider mite resistance could be established.     

Effects of pine-produced chemicals on selected understory species in aPinus ponderosa community

Pinus ponderosa accounted for more than 98% of all tree and shrub stratum stems in a climax community with low herb coverage and aboveground biomass, 35% and 60 g/m², respectively. Because of our previous report that nitrification and nitrifying bacteria in the same community were allelopathically inhibited, we speculated that the pine-produced allelochemics might also directly influence the development and growth of the herb stratum. In most cases decaying needles, needle leachate, and field soils significantly reduced germination and radicle growth ofAndropogon gerardii andA. scoparius, pine-associated herbaceous species. Additionally, growth ofAndropogon scoparius seedling radicles was reduced 28–56% by pine needle extracts, 33% by pine bark extracts, and 67% by soil hydrolysate extracts.Andropogon seed germination was reduced 20–25% by pine needles and soil. Phytotoxins identified in various plant parts and associated soils were caffeic acid, chlorogenic acid, quercetin, and condensed tannins. Pine needle water and soil hydrolysate extracts were most inhibitory to the radicle growth of the test species. Thus it appears that the limited growth of the herbaceous stratum in the pine community may be accounted for, in part, by allelopathy. Such allelopathic interactions may have an adaptive ecological significance in various forest and other plant communities.     

Interspecific inhibition of the response of the bark beetles,Dendroctonus brevicomis andIps paraconfusus,to their pheromones in the field

Ponderosa pine logs infested withIps paraconfusus males inhibited the attraction ofDendroctonus brevicomis in the field to either attractive logs cut from a ponderosa pine tree under attack byD. brevicomis or to their synthetic pheromones,exo-brevicomin, frontalin, and myrcene. Logs cut from trees under attack byD. brevicomis inhibited the response ofI. paraconfusus to logs infested with maleI. paraconfusus.Exo-brevicomin, frontalin, and myrcene did not inhibit their response but verbenone did. Verbenone was found in maleD. brevicomis dissected from attractive logs under attack during the same time the response ofI. paraconfusus was inhibited by these logs.Trans-verbenol andexo-brevicomin were found in femaleD. brevicomis while verbenone,trans-verbenol, and frontalin were found in maleD. brevicomis in relatively large amounts near the beginning of the aggregation phase of host colonization. All of these compounds had decreased at a similar rate 5 days later. This gradual decrease inexo-brevicomin and frontalin probably caused the observed reduction in attraction. The ecological significance of these compounds in relation to termination of the aggregation phase ofD. brevicomis and reduction of interspecific competition is discussed.Coleoptera: Scolytidae. This paper is based in part upon a dissertation submitted by J.A.B. to the University of California, Berkeley, in partial fulfillment of the requirements for the PhD in entomology. These studies were supported in part by the Rockefeller Foundation; U.S. Forest Service; Regional research Project W-110, S.E.A./ U.S.D.A.; and the National Science Foundation and Environmental Protection Agency through a grant (NSF GB-34719/BMS 75-04223) to the University of California.     

Byrsonic Acid—the Clue to Floral Mimicry Involving Oil-Producing Flowers and Oil-Collecting Bees

Tetrapedia diversipes and other Apidae (Anthophoridae) may be deceived by floral similarities between Malpighiaceae and Orchidaceae of the Oncidiinae subtribe. The latter do not usually exudate floral oils. Thus, visitors may pollinate the flowers in a deceit/food/pollination syndrome. We studied the chemical compositions of Byrsonima intermedia (Malpighiaceae) floral oil and T. diversipes (Anthophoridae) cell provisions. From B. intermedia floral oil, we isolated a novel fatty acid (3R, 7R)-3,7-diacetoxy-docosanoic acid, here named byrsonic acid, and from T. diversipes cell provisions we isolated two novel fatty acid derivatives 3,7-dihydroxy-eicosanoic acid and 3,7-dihydroxy-docosanoic acid, here named tetrapedic acids A and B, respectively. The three fatty acid derivatives have common features: possess long chains (20 or 22 carbon atoms) with no double bond and either hydroxy or acetoxy groups at carbons 3 and 7. This characteristic was also encountered in the fatty acid moiety of oncidinol (2S, 3′R, 7′R)-1-acetyl-2-[3′, 7′-diacetoxyeicosanyl)-glycerol, a major floral oil constituent of several Oncidiinae species (Orchidaceae). Thus, both tetrapedic A (C20) and B (C22) could be the biotransformation products of oncidinol and byrsonic acid by T. diversipes hydrolases. These are the chemical clues for bee visitation and oil collecting from both plant species. The results indicate that the deceit/pollination syndrome should not be applied to all Oncidiinae flowers.     

Variation in Growth, Chemical Defense, and Herbivore Resistance in Scots Pine Provenances

Variation in the growth, chemical defense, and susceptibility to monophagous and polyphagous sucking herbivores was assessed for four Scots pine (Pinus sylvestris) provenances in Petri dish and pot experiments. Seed provenances, Muonio (MU), Suomussalmi (SU), Korpilahti (KO), and Saaremaa (SA) represented a 1200-km N–S gradient. Scots pines from SU were least preferred as a host plant by pine-feeding aphids Schizolachnus pineti Fabr. and Eulachnus agilis, and in pot experiments, pines from SA were most preferred. S. pineti also produced the fewest nymphs on pines from SU. Polyphagous Lygus rugulipennis laid significantly fewer eggs on pines from MU provenance, which were smaller than seedlings from other provenances. The total and some individual terpene concentrations increased, while the total resin acid concentration decreased, towards the north. The absolute concentrations of total or individual terpenes and resin acids in the needles of unfavored SU plants did not differ significantly from the other provenances. Only the proportional quantity of dehydroabietic acid was higher in SU plants than in KO plants, and it correlated, together with sandaracopimaric acid, negatively with the number of S. pineti nymphs in the reproduction experiment. Conversely, absolute concentrations of some terpenes correlated negatively and some resin acids positively with the number of S. pineti nymphs. The length and weight of shoots decreased towards the north, adequately explaining the number of Lygus eggs and the final numbers of both aphids. The results suggest that seedling size is a better estimator of susceptibility of pine seedlings to both specialist and generalist sucking insects than relative or absolute concentrations of monoterpenes and resin acids.     

Antimicrobial activity of dogwood fruits (Cornus drummondii) from winter food caches of eastern woodrats (Neotoma floridana)

Post-harvest loss of resources to microbial competitors affects a number of species of animals, and many of them have evolved behaviors that reduce the likelihood of such loss. We previously described the inhibition ofBacillus psychrophilus by dogwood fruits (Cornus drummondii), which can comprise a significant portion of the winter food cache of the eastern woodrat (Neotoma floridana). The present study is a further investigation of the ability of dogwood fruits to inhibit growth ofB. psychrophilus. Additionally, we tested the antimicrobial activity of dogwood fruits onEscherichia coli andStaphlococcus aureus. Results of our study indicate that fresh fruits inhibit the growth ofB. psychrophilus andS. aureus but notE. coli. However, fruits taken from woodrat dens after four and six months storage inhibited growth of all three species of bacteria. Further, the strength of inhibition increased over the test period. We suggest the presence of an inhibitor allows woodrats to compete effectively for a valuable and limited food resource.     

Role of phenolics of coniferous trees as deterrents against debarking behavior of meadow voles (Microtus pennsylvanicus)

Preferences of meadow voles (Microtus pennsylvanicus) toward various coniferous species were tested under winter conditions. Cafeteria tests showed preferences for Norway spruce (Picea abies) and Norway pine (Pinus resinosa) and rejection of white pine (Pinus strobus) and white spruce (Picea glauca). When phenolic extracts of these species were prepared and added to a low 8% protein diet, food intake of voles and preferences by rank followed the same patterns. Determination of the concentration of phenolics in branch samples using the Singleton and Rossi procedure showed that Norway pines contained the smallest amount (2.15%/g dry matter) while spruces yielded the most (2.76%/g dry matter). These experiments lead us to expect high losses of Norway pine and Norway spruce in habitats harboring high vole densities.     

Defensive mechanisms of loblolly and shortleaf pine against attack by southern pine beetle,Dendroctonus frontalis Zimmermann,and its fungal associate,Ceratocystis minor (Hedgecock) Hunt

Loblolly and shortleaf pine growing on a single site in the North Carolina piedmont were examined to determine similarities and differences in their defensive mechanisms against the southern pine beetle,Dendroctonus frontalis Zimmermann, and its fungal associate,Ceratocystis minor (Hedgecock) Hunt. Both species responded to wounding and fungal inoculation by forming a hypersensitive lesion around the wound site. There were significantly less soluble sugars and more monoterpenes in the lesion tissue than in unwounded inner bark. The two species were similar in resin flow rate and inner bark soluble sugar content, but the loblolly pines had thicker bark, longer hypersensitive lesions, and a higher concentration of inner bark monoterpenes. Inner bark monoterpene composition was also significantly different between the two pine species. It is hypothesized that two different defensive strategies against southern pine beetle attack may be utilized.     

Effects of monoterpene odors on food selection by red deer calves (Cervus elaphus)

The response of red deer calves (Cervus elaphus) to the odors of Sitka spruce (Picea sitchensis) and lodgepole pine (Pinus conforta) needles and five monoterpene constituents of their essential oils was measured by simple two-choice feeding trials. All odors were significantly rejected (P < 0.05) except Sitka spruce and lodgepole pine by females and Sitka spruce and alpha-terpineol by males. Females had a stronger dislike of all odors except lodgepole pine than males. Rejection of monoterpene odors weakened slightly with time. A strong logarithmic relationship between the strength of the rejection response and vapor pressure of the compounds tested suggested that the odors were rejected on the basis of concentration rather than quality.Research supported by the Natural Environment Research Council and the Forestry Commission.     

Effects of bilberry (Vaccinium myrtillus L.) litter on seed germination and early seedling growth of four boreal tree species

Laboratory and greenhouse bioassays were used to test for inhibitory effects of senescent and decomposed leaves and aqueous extract from bilberry (Vaccinium myrtillus L.) against seed germination and seedling growth of aspen (Populus tremula L.), birch (Betula pendula Roth.), Scots pine (Pinus sylvestris L.), and Norway spruce [Picea abies (L.) Karst.]. Aqueous extracts from bilberry leaves were inhibitory to aspen seed germination and seedling growth and also induced root damage and growth abnormalities. Addition of activated carbon removed the inhibitory effects of extracts. Senescent leaves reduced pine and spruce seed germination, but rinsing of seeds reversed this inhibition. Senescent leaves were more inhibitory than decomposed leaf litter, suggesting that the inhibitory compounds in bilberry leaves are relatively soluble and released at early stages during decomposition. Spruce was generally less negatively affected by litter and aqueous extracts than the other tested species. This study indicates that chemical effects of bilberry litter have the potential to inhibit tree seedling recruitment, but these effects were not consistently strong. Phytotoxicity is unlikely to be of critical importance in determining success for spruce seedling establishment.     

Leaf Ontogeny Influences Leaf Phenolics and the Efficacy of Genetically Expressed Bacillus thuringiensis cry1A(a) d-Endotoxin in Hybrid Poplar Against Gypsy Moth

We tested the hypothesis that ontogenetic variation in leaf chemistry could affect the efficacy of genetically expressed Bacillus thuringiensis cry1A(a) d-endotoxin, and thus provide spatial variation in (1) foliage protection and (2) selective pressures that could delay the resistance of folivores. Our model consisted of clonal hybrid Populus plants (NC5339). Consumption of foliage and relative growth rates of gypsy moth, Lymantria dispar (L.) increased, and phenolic glycoside concentrations decreased, as leaves from transformed plants containing the cry1A(a) d-endotoxin and nontransformed plants matured from leaf plastochron index (LPI) 1–6. Feeding and growth rates were negatively correlated with phenolic glycosides in both transformed and nontransformed foliage. The presence of the B. thuringiensis d-endotoxin was at most, additive to the effect of the phenolic glycosides. Feeding and growth rates were positively correlated with condensed tannins in transformed foliage, but there was no relationship with condensed tannins in nontransformed foliage. The results indicate that the presence of foliar allelochemicals of poplar can enhance the effectiveness of genetically expressed B. thuringiensis d-endotoxin against gypsy moth larvae. However, the spatial variation in gypsy moth performance in response to the combination of foliar allelochemicals and d-endotoxin was not greater than the effect of ontogenetic variation in foliar allelochemicals alone. These results suggest that for this important pest, foliage protection may be obtained without genetically engineered defenses, and instead, by relying on ontogenetic and clonal variation in allelochemicals. The benefits of combining novel resistance mechanisms with natural ones will depend upon the specific folivore's adaptation to natural resistance mechanisms, such as allelochemicals. Moreover, some of the greatest benefits from transgenic resistance may arise from the need to protect trees from multiple pests, some of which may not be deterred by, or may even prefer, allelochemicals that confer protection from a few species.     

Resistance of western white pine to feeding and oviposition byPissodes strobi peck in western canada

Forced and choice feeding and oviposition experiments were conducted by caging overwinteredPissodes strobi on lateral branches or leaders of sympatric Engelmann spruce and/or western white pine trees in Manning Provincial Park, British Columbia, or on transplanted, potted trees in Burnaby, British Columbia. Whereas femaleP. strobi preferred to feed on 1-year-old Engelmann spruce lateral branches in both the forced- and choice-feeding experiments, male weevils failed to discriminate between this host and western white pine. Forced-feeding experiments that utilized 1-year-old leaders demonstrated that western white pine is an acceptable host forP. strobi feeding, but that the native host, Engelmann spruce, is preferred under choice conditions. In all experiments, female weevils oviposited only on Engelmann spruce. These results indicate that the releasing stimulus for feeding is present in the bark of both conifer species and suggests that a separate releasing stimulus for oviposition is absent from western white pine.Coleoptera: Curculionidae.Research supported by Canadian Forestry Service Science Subvention Grant, National Science Foundation (USA) Grant No. BMS-7413643, and National Research Council (Canada) Grant No. A3881.     

Antennal responses of the two host races of the larch bud moth,Zeiraphera diniana,to larch and cembran pine volatiles

The larch bud moth (LBM) Zeiraphera diniana Guenée causes defoliation on larch in the Alps at 8- to 10-year intervals, after which populations crash. There are two LBM host races, one on larch and the other on cembran pine. These host races are morphologically indistinguishable as adults but they differ genetically in larval color types. Furthermore, females of each host race produce distinct pheromone blends and show oviposition preferences for their respective hosts. It is not clear to what extent host choice contributes to assortative mating in the LBM. Here, we compare the olfactory sensitivities of the two host races to the odors of fresh foliage of the host plants using the electroantennogram (EAG) technique, and the responses of the two host races to volatiles collected from the two host plants as analyzed by gas-chromatography-linked antennographic detection (GC-EAD). Both sexes of the larch and cembran host races show the same EAG responses to vapors of fresh larch and cembran pine foliage. Fifteen plant volatiles identified as chemostimuli by GC-EAD from larch and cembran pine odors elicited the same antennogram responses from the two host races. However, the GC-EAD analyses indicate that the number and quantity of chemostimuli emanating from each host plant is different. It is, therefore, most probably the array of olfactory receptors responding to the bouquet of volatiles unique to each host plant that underlies the host preferences of the two races. What remains open is the extent to which the similarity of the olfactory systems may contribute to cross-attraction. The fact that LBM individuals with intermediate characteristics between the two host races exist, suggests that olfactory perception does not hinder gene flow and contributes to sustained genetic diversity within the species Z. diniana.     

Soldier defense secretions ofTrinervitermes bettonianus (Isoptera,Nasutitermitinae): Chemical variation in allopatric populations

The soldier defense secretions of major and minor soldiers of the East African nasute termiteTrinervitermes bettonianus were analyzed chromatographically and spectrometrically, and the diterpene and monoterpene constituents were determined for three allopatric populations. Incipient colonies from one population raised on food from a second population produced their population-specific terpene pattern independent of food source. Secretion compositions are thus genetically rather than nutritionally determined, in agreement with biosynthetic studies in other nasutes. A minor volatile constitutent, previously proposed to be 3-ethyl-2-octanol was re-identified as (R)-2-decanol.     

Improvement of the growth of Arthrospira (Spirulina) platensis from Toliara (Madagascar): Effect of agitation, salinity and CO2 addition

Arthrospira (Spirulina) platensis Toliara isolated from alkaline and salt lakes in the south-western area of Madagascar is a potential source of proteins that could efficiently fight against food deficiency in developing countries like Madagascar. Up to now, productivity in this country has been low, so a better understanding of the growth conditions of this species is needed to improve its production. Growth experiments were undertaken in bubble columns at laboratory scale. The influence of agitation of the culture, medium salinity (ranging from 13 to 35 g L⁻¹) and CO₂ addition (ranging from 0 to 2%, v/v) on growth and protein content was examined. Because Arthrospira cells are fragile, a bubble column without additional mixing gave the best growth. Arthrospira (Spirulina) platensis showed higher specific growth rate (μ_max) and protein content for lower salinity. Addition of 1% of CO₂ improved the productivity by near 60%. The feasability of semi-continuous culture was demonstrated and optimal culture conditions led to a mean productivity of 0.22 ± 0.03 g L⁻¹ d⁻¹, a mean specific growth rate of 0.015 ± 0.002 h⁻¹ and a protein content of 53 ± 2% of total dry weight.