The trimorphic flea-beetle, <Emphasis Type="Italic">Alagoasa extrema</Emphasis>, not suitable for biocontrol of <Emphasis Type="Italic">Lantana camara</Emphasis> in Africa

The biology and host range of the flea-beetle, Alagoasa extrema (Harold) (Coleoptera: Chrysomelidae: Galerucinae: Alticini), was studied under quarantine laboratory conditions to evaluate the insect’s suitability for release as a biological control agent for the noxious weed, Lantana camara L. (Verbenaceae), in South Africa. Identification of this species proved noteworthy. The adults of A. extrema display three freely interbreeding and very distinct colour morphs, which can be confused with no less than 11 species of Alagoasa found in Mexico and the southwestern U.S. Initially, specimens were identified as two species of the genus Alagoasa Bechyné, i.e. A. quadrilineata (Harold) and A. extrema. Thirteen additional Alagoasa species and Kushelina petaurista (F). that can be confused with A. extremabased on external morphology of adults or larvae are discussed. Favourable biological characteristics included long-lived adults, several overlapping generations per year, and high adult and larval feeding rates. Observations from the insect’s native Mexican range and studies in South Africa suggest that A. extrema would probably be more suited to subtropical, rather than temperate areas in Africa. Host-specificity studies showed A. extrema to be an oligophagous species, capable of feeding and developing on several non-target species, especially two indigenous, African Lippia species (Verbenaceae). The host suitability of these indigenous species was only marginally lower than that of L. camara, and the potential risk to them was deemed to be too high to warrant release. It was therefore recommended that A. extrema be rejected as biocontrol agent for lantana in Africa.     

The effect of <Emphasis Type="Italic">Lantana camara</Emphasis> leaf quality on the performance of <Emphasis Type="Italic">Falconia intermedia</Emphasis>

The sap-sucking mirid, Falconia intermedia (Distant) (Hemiptera: Miridae), released as a biological control agent of Lantana camara L. (Verbenaceae) in South Africa in 1999, has established at only one site. We investigated the role of induced plant defences as a possible explanation for this lack of establishment. F. intermedia inoculated plants from the five test varieties significantly increased the toughness of their new leaves compared to control plants. Additionally, plants from three L. camara varieties significantly increased leaf trichome density on new leaves after prolonged feeding by F. intermedia, significantly reducing F. intermedia oviposition, survival and feeding damage. The defensive responses were systemic and rapidly induced about eight weeks after insect feeding. We suggest that these leaf quality responses played a role in the non-establishment of F. intermedia in South Africa.     

Nutritional suitability and ecological relevance of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> and <Emphasis Type="Italic">Brassica oleracea</Emphasis> as foodplants for the cabbage butterfly, <Emphasis Type="Italic">Pieris rapae</Emphasis>

The thale cress, Arabidopsis thaliana, is considered to be an important model species in studying a suite of evolutionary processes. However, the species has been criticized on the basis of its comparatively small size at maturity (and consequent limitations in the amount of available biomass for herbivores) and on the duration and timing of its life cycle in nature. In the laboratory, we studied interactions between A. thaliana and the cabbage butterfly, Pieris rapae, in order to determine if plants are able to support the complete development of the herbivore. Plants were grown in pots from seedlings in densities of one, two, or four per pot. In each treatment, one, two, or five newly hatched larvae of P. rapae were placed on fully developed rosettes of A. thaliana. In a separate experiment, the same densities of P. rapae larvae were reared from hatching on single mature cabbage (Brassica oleracea) plants. Pupal fresh mass and survival of P. rapae declined with larval density when reared on A. thaliana but not on B. oleracea. However, irrespective of larval density and plant number, some P. rapae were always able to complete development on A. thaliana plants. A comparison of the dry mass of plants in different treatments with controls (= no larvae) revealed that A. thaliana partially compensated for plant damage when larval densities of P. rapae were low. By contrast, single cress plants with 5 larvae generally suffered extensive damage, whereas damage to B. oleracea plants was negligible. Rosettes of plants that were monitored in spring, when A. thaliana naturally grows, were not attacked by any insect herbivores, but there was often extensive damage from pulmonates (slugs and snails). Heavily damaged plants flowered less successfully than lightly damaged plants. Small numbers of generalist plant-parasitic nematodes were also recovered in roots and root soil. By contrast, plants monitored in a sewn summer plot were heavily attacked by insect herbivores, primarily flea beetles (Phyllotreta spp.). These results reveal that, in natural populations of A. thaliana, there is a strong phenological mismatch between the plant and most of its potential specialist insect herbivores (and their natural enemies). However, as the plant is clearly susceptible to attack from non-insect generalist invertebrate herbivores early in the season, these may be much more suitable for studies on direct defense strategies in A. thaliana.     

Biological control of <Emphasis Type="Italic">Lantana camara</Emphasis> in South Africa: targeting a different niche with a root-feeding agent, <Emphasis Type="Italic">Longitarsus</Emphasis> sp.

The root-feeding flea beetle, Longitarsus sp. (Coleoptera: Chrysomelidae: Alticinae), was studied as a potential biological control agent for Lantana camara L. (Verbenaceae) in South Africa. Host range tests were carried out on 52 plant species in 11 families. Although 11 plant species, all in the family Verbenaceae, supported complete development of Longitarsus sp. during no-choice tests, the beetles showed very strong preferences for L. camara during paired-choice and multi-choice tests. The results confirm that the beetles have a narrow host range, and that under natural conditions they are highly unlikely to utilise plants other than L. camara. In the unlikely event that some of the Lippia spp. are attacked in the field, they are not expected to sustain populations of the flea beetle over time. Attributes that should enhance the biocontrol potential of Longitarsus sp. include: the adults are long-lived and highly mobile; and, the larvae cause extensive direct damage to the roots of L. camara, which could in turn expose the plants to soil-born pathogens. All indications are that Longitarsus sp. could make a substantial contribution to the biological control of L. camara in many countries around the world because the beetles pose no threat to non-target plant species and they damage a part of the plant (i.e. roots) not yet affected by any other agent species.     

Development of <Emphasis Type="Italic">Mamestra brassicae</Emphasis> and its solitary endoparasitoid <Emphasis Type="Italic">Microplitis mediator</Emphasis> on two populations of the invasive weed <Emphasis Type="Italic">Bunias orientalis</Emphasis>

The warty cabbage Bunias orientalis is an invasive pest in much of central Europe, including much of Germany since the 1980s, whereas in other countries, such as The Netherlands, it is a less common exotic species. Here, healthy larvae of Mamestra brassicae, which has been found feeding on B. orientalis plants in Germany, and larvae parasitized by one of its major larval endoparasitoids Microplitis mediator, were reared on both herbivore-induced and noninduced leaves of B. orientalis originating from single large populations growing in The Netherlands and central Germany. Herbivore performance was less negatively affected than parasitoid performance by differences in plant quality. Development times in both M. brassicae and Mi. mediator were shorter on Dutch than German plants and also shorter on noninduced than induced plants. Moreover, survival and body size of the parasitoid was more strongly affected by plant population and induction than survival of healthy M. brassicae. Chemical analyses of defensive secondary metabolites [glucosinolates (GS)] revealed that concentrations of the major GS sinalbin were constitutively expressed in German plants whereas they were induced in Dutch plants. However, in separate feeding bioassays in which preference for induced and noninduced leaves was compared separately, L3 instars of M. brassicae preferred noninduced German plants over Dutch plants but induced Dutch plants over German plants, revealing that changes in primary metabolites or an unidentified non-GS compound mediates population-related differences in plant quality. The results reveal asymmetric effects of plant quality in exotic plants on organisms in the second and third trophic level.     

Fecundity and feeding of <Emphasis Type="Italic">Galerucella calmariensis</Emphasis> and <Emphasis Type="Italic">G. pusilla</Emphasis> on <Emphasis Type="Italic">Lythrum salicaria</Emphasis>

Fecundity and feeding of two introduced sibling biological control species, Galerucella calmariensis and G. pusilla (Coleoptera: Chrysomelidae) on purple loosestrife, Lythrum salicaria L. (Lythraceae) were compared at constant temperatures of 12.5, 15, 20, 25, and 27.5 °C. Larval feeding was also carried out at 30 °C, but at this temperature, larvae developed only to the L2 stage and none pupated. Thus, data for this temperature were not used in the analysis. There were significant species × temperature interactions in fecundity. Of the two species, Galerucella pusilla laid more eggs. Although egg production of both species was lowest at 12.5 °C and increased to 20 °C, at higher temperatures, the two species reacted differently. From 25 to 27.5 °C, egg production decreased for G. pusilla, but G. calmariensis fecundity peaked at 27.5 °C. Significant temperature × species × life-stage interactions were also observed in feeding. For each species, the amount of feeding varied with temperature and stage of development. Galerucella pusilla adults consumed more foliage at 15, 20, and 27.5 °C. However, at 12.5 °C G. calmariensis adults fed more than G. pusilla. G. pusilla larvae consumed an average of 25% less foliage than G. calmariensis. The lower larval consumption of G. pusilla suggests that when food is limited, G. pusilla larvae may have a higher survival rate because of its ability to complete larval development with less food and produce more progeny due to its greater fecundity. When food is not limited neither species would have a competitive advantage and both species could coexist temporally and spatially. However, since G. calmariensis larvae consumed more leaf material, the larval stage of this species would have a greater impact on purple loosestrife than G. pusilla.     

<Emphasis Type="Italic">Piriformospora indica</Emphasis> and <Emphasis Type="Italic">Sebacina vermifera</Emphasis> increase growth performance at the expense of herbivore resistance in <Emphasis Type="Italic">Nicotiana attenuata</Emphasis>

A Sebacinales species was recovered from a clone library made from a pooled rhizosphere sample of Nicotiana attenuata plants from 14 native populations. Axenic cultures of the related species, Piriformospora indica and Sebacina vermifera, were used to examine their effects on plant performance. Inoculation of N. attenuata seeds with either fungus species stimulated seed germination and increased growth and stalk elongation. S. vermifera inoculated plants flowered earlier, produced more flowers and matured more seed capsules than did non-inoculated plants. Jasmonate treatment during rosette-stage growth, which slows growth and elicits herbivore resistance traits, erased differences in vegetative, but not reproductive performance resulting from S. vermifera inoculation. Total nitrogen and phosphorous contents did not differ between inoculated and control plants, suggesting that the performance benefits of fungal inoculation did not result from improvements in nutritional status. Since the expression of trypsin proteinase inhibitors (TPI), defensive proteins which confer resistance to attack from Manduca sexta larvae, incur significant growth and fitness costs for the plant, we examined the effect of S. vermifera inoculation on herbivore resistance and TPI activity. After 10 days of feeding on S. vermifera-inoculated plants, larval mass was 46% higher and TPI activity was 48% lower than that on non-inoculated plants. These results suggest that Sebacina spp. may interfere with defense signaling and allow plants to increase growth rates at the expense of herbivore resistance mediated by TPIs.     

Risk to nontarget plants from <Emphasis Type="Italic">Ophraella communa</Emphasis> (Coleoptera: Chrysomelidae), a potential biological control agent of alien invasive weed <Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> (Asteraceae) in China

Ophraella communa LeSage is an oligophagous insect that shows promise for controlling the alien invasive weed Ambrosia artemisiifolia L. in China. This study was performed to evaluate the risk of O. communa on the basis of host-specificity testing of larval development under no-choice conditions and of oviposition preferences under choice conditions in greenhouses and in the open field. Under no-choice conditions, O. communa larvae experienced much higher mortality rates on the nontarget plants than on the target weed, but a small proportion of larvae completed development on the nontarget plants examined, including Xanthium sibiricum Patrin ex Widder, Helianthus tuberosus L., and H. annuus L. Multiple-choice tests indicated that O. communa showed a strong oviposition preference for the target weed over the nontarget plants and laid few eggs on the economically important Helianthus crops tested. In paired-choice trials, O. communa adults showed an obvious preference for the target weed over X. sibiricum but preferred X. sibiricum to H. annuus. The results suggest that X. sibiricum might be used as a lower-ranked host plant next to the target weed by O. communa, and that Helianthus crops would not be at risk of being used for oviposition in the field.     

Biology and host range of <Emphasis Type="Italic">Aconophora compressa,</Emphasis> a candidate considered as a biocontrol agent of <Emphasis Type="Italic">Lantana camara</Emphasis> in Africa

The shrub, Lantana camara L. (Verbenaceae), of tropical American origin, is a serious weed in South Africa and is the target of a biological control programme. The stem-sucking membracid, Aconophora compressa Walker (Homoptera: Membracidae), from Mexico was reported to be very damaging and was therefore imported into South Africa for biology and host range studies. The female partially inserts the eggs into the woody portion of actively growing stems, and guards them against potential predators. Nymphs develop through five instars to the adult stage in about 45 days. The adults and nymphs feed on the sap of stems causing the leaves to wilt, the flowers to abort and the gradual dieback of stems. No-choice experiments showed that adult survival, egg production, and nymphal emergence was high on L. camara, and also on related ornamental and indigenous species. The adult reproductive performance was higher on some indigenous Lippia species than on L. camara. Furthermore, the nymphs developed faster on these indigenous species and high rates of reproductive performance on these non-target species were sustained over several generations. In multiple-choice trials, equal or larger numbers of egg batches were recorded from indigenous Lippia species and the ornamental plant, Aloysia citrodora Palau, than on L. camara. The treehopper, A. compressa, poses an unacceptable threat to indigenous Lippia species and has therefore been rejected as a biocontrol agent for L. camara in Africa.     

Parasitism and developmental parameters of the parasitoid <Emphasis Type="Italic">Diadegma</Emphasis><Emphasis Type="Italic">majale</Emphasis> (Gravenhorst) in control of <Emphasis Type="Italic">Plutella xylostella</Emphasis> (L.) on selected cultivars of canola

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is one of the most economically significant pests of canola, Brassica napus L., in Ardabil region, Iran. Use of host plant resistance integrated with biocontrol agents such as Diadegma majale (Gravenhorst) (Hymenoptera: Ichneumonidae) is an essential component of integrated management of P. xylostella. In this study, we investigated the parasitism by D. majale on six selected cultivars of canola under field conditions and preference and performance of the parasitoid on P. xylostella larvae under laboratory conditions. In field experiments, the highest larval density of P. xylostella was observed on Zarfam during 2008 and 2009. Larval densities were not significantly different among Opera, Hyola 401, Okapi, and Option 500 and Elite in 2008, but the lowest larval density was observed on Opera in 2009. No significant differences were observed among the rate of parasitized larvae on tested cultivars in 2008, while in 2009 the parasitism rate was significantly higher on Opera than on Zarfam. In free-choice situations, the percentage of parasitized larvae was significantly highest on Opera (88.7%) and lowest on Zarfam (62.95%). Developmental time from egg to adult, body mass, length of forewings and hindwings, length of hind femur and hind tibia of D. majale females reared on larvae of P. xylostella fed on Opera did not differ from other cultivars. Our results suggest that cultivation of Opera integrated with D. majale could provide effective and sustainable management of P. xylostella in the region.     

Effects produced by the feeding of larvae of <Emphasis Type="Italic">Ornithodoros</Emphasis> aff. <Emphasis Type="Italic">puertoricensis</Emphasis> (Acari: Argasidae) on laboratory mice

The clinical picture produced by the feeding of larvae of Ornithodoros aff. puertoricensis on laboratory mice, was studied using different larval infestation protocols that included 30, 40 or 50 larvae per mouse and control uninfested groups. Clinical effects appeared around 72 h of larval feeding, having a first stage characterized by hyperaemia in both nasal and ocular mucosa, followed by respiratory symptoms (96–120 h) and nervous incoordination (120–144 h). No one mouse evidenced paralysis, and nervous symptoms were never observed in animals infested with only 30 larvae. High mortality (commonly up to 70%) was observed in mice with respiratory symptoms, while 100% of animals in the nervous phase died between 168 and 192 h after the beginning of larval feeding. When some infested mice were treated with a solution of Amitraz the larvae were killed and reversion of symptoms was observed. These effects are ascribed to the presence of a toxin in the saliva of the feeding larvae.     

The influence of two endoparasitic wasps, <Emphasis Type="Italic">Hyposoter didymator</Emphasis> and <Emphasis Type="Italic">Chelonus inanitus</Emphasis>, on the growth and food consumption of their host larva <Emphasis Type="Italic">Spodoptera littoralis</Emphasis>

The influence of parasitism by Hyposoter didymator (Thunberg; Hymenoptera: Ichneumonidae) and Chelonus inanitus (Linnaeus) (Hymenoptera: Braconidae) on the growth and food consumption of their host Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) was studied in the laboratory. Parasitised larvae consumed significantly less artificial diet than unparasitised ones. Egg parasitisation by C. inanitus affected host larval consumption from the second day after emergence and it was significantly different from that of unparasitised ones. H. didymator, however, started to reduce larval consumption 4 days after parasitisation on the third instar host larvae. The overall reduction achieved by the larval endoparasitoid H. didymator is higher than that caused by the egg-larval endoparasitoid C. inanitus. The final body weight of a parasitised host larva by H. didymator and C. inanitus was only 6.7 and 13.0% of the maximum weight of an unparasitised sixth instar larva respectively. Moreover, parasitised larvae never reached the last instar. Results indicated that parasitised larvae might cause considerable less damage to the host plant than unparasitised ones.     

Biology,host range and varietal preference of the leaf-feeding geometrid, <Emphasis Type="Italic">Leptostales ignifera</Emphasis>, a potential biocontrol agent for <Emphasis Type="Italic">Lantana camara</Emphasis> in South Africa,under laboratory conditions

Lantana camara L. (Verbenaceae) is a weed of major importance in South Africa. It invades indigenous forests and veld, valuable commercial and agricultural forests, plantations and orchards, as well as river-catchment areas. Several natural enemies, including insect and pathogen species, have been released in South Africa, some of which established successfully. These do not exert sufficient control and additional natural enemies are required. Leptostales ignifera Warren (Lepidoptera: Geometridae), one of several new species being investigated as potential biocontrol agents, was collected in the subtropical parts of Florida, USA and Mexico. Host specificity trials indicated L. camara to be the preferred host plant of this quick-developing, voracious leaf-feeder, with some of the African indigenous Lippia species qualifying as very marginal hosts. The possible preference that L. ignifera might have for different South African naturalized L. camara varieties was studied during quarantine laboratory preference trials. Variety 029WP was the most suitable host for L. ignifera, although the other four tested varieties were able to support viable populations of the insect. Not taking other abiotic and biotic factors such as climate and predation into consideration, once released, L. ignifera should be able to establish on all five of the tested varieties in the field and contribute to the biological control of the complex of L. camara as a whole. Based on the above studies, permission has been granted for the release of L. ignifera in South Africa.     

RETRACTED ARTICLE: Foraging of Host-Habitat and Superparasitism in <Emphasis Type="Italic">Cotesia glomerata</Emphasis>: A Gregarious Parasitoid of <Emphasis Type="Italic">Pieris brassicae</Emphasis>

The study investigates differences in the oviposition pattern of a braconid parasitoid, Cotesia glomerata (Linn.) in Pieris brassicae (Linn.) in relation to their use of different cruciferous food plants. The response of P. brassicae to superparasitism and consequences for the parasitoid were examined in order to elucidate the ecological significance of this behaviour. Female parasitoid located various crucifers and searched for host more frequently almost on all the host plants tested i.e. cabbage, cauliflower, Chinese cabbage, broccoli and radish. According to the estimated relative number of female locating hosts, cabbage was the most attractive plant for C. glomerata and total number of eggs laid in host larvae feeding on it was higher than in larvae feeding on other plants. Laboratory experiments demonstrated that superparasitism reduced survivorship of P. brassicae larvae. Superparasitism lengthened parasitoid development and prolonged the feeding period of host larvae. Sex ratio and the body weight of emergent wasps correlated negatively with brood size. Despite a trade-off between maximising brood size and optimising the fitness of individual offspring, two or three ovipositions on P. brassicae larvae resulted in a greater female dry mass than did a single oviposition on the host. Thus, superparasitism might be of adaptive significance under certain circumstances, especially when host density is low and unparasitized hosts are rare in a habitat.     

Genetic determination of tannins and herbivore resistance in <Emphasis Type="Italic">Quercus ilex</Emphasis>

Genetic variability of trees influences the chemical composition of tissues. This determines herbivore impact and, consequently, herbivore performance. We evaluated the independent effects of plant genotype and provenance on the tannin content of holm oak (Quercus ilex) and their consequences for herbivory and performance of gypsy moth (Lymantria dispar) larvae. Oak seedlings of 48 open-pollinated families from six populations were grown in a common garden in central Spain. Half the plants were subjected to defoliation by gypsy moth larvae and the other half were destructively sampled for chemical analysis. Tannin content of leaves did not differ significantly among populations but differed significantly among families. Estimates of heritability (h ²) and quantitative genetic differentiation among populations for tannin content (Q _ST) were 0.83 and 0.12, respectively. Defoliation was not related to the tannin content of plants nor to spine and trichome densities of leaves, although positive family–mean associations were observed between defoliation and both seed weight and plant height (P < 0.003). Among the oak populations, differential increase in larval weight gain with defoliation was observed. Leaf tannin content in Q. ilex is genetically controlled but does not influence defoliation or predict performance of the larvae. Different efficiencies of food utilisation depending on the oak genotypes indicate that other plant traits are influencing the feeding patterns and fitness of L. dispar and consequent population dynamics.     

<Emphasis Type="Italic">Nimbya alternantherae</Emphasis> a potential biocontrol agent for alligatorweed, <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis>

Alligatorweed, (Alternanthera philoxeroides (Mart.) Griseb.), an aquatic and wetland plant native to South America, is an aggressive weed in many parts of the world. Its ability to compete with other native plants and to impede waterways has made it a serious threat to aquatic ecosystems. Although biological control with insects has been fairly successful in aquatic habitats, there is a need for additional agents to manage the weed in upland sites. Accordingly, in a survey in Brazil in 1997 a fungus, Nimbya (=Alternaria) alternantherae (Holcomb and Antonopoulus) Simmons and Alcorn, was discovered and confirmed to be highly damaging to alligatorweed. Studies were conducted to determine the potential of this fungus for controlling this weed. Several isolates from Brazil, USA, and Puerto Rico were compared and no differences in virulence were observed, although a lower dew requirement was demonstrated for the Brazilian isolates. Conidia were more effective than mycelial suspension, and inoculum concentrations of 1×10⁵ and 1×10⁶ conidia per ml provided significant levels of control of the weed in greenhouse and field experiments, respectively. In a host-range study, N. alternantherae infected 6 plant species from a total of 42 species belonging to 23 families. N. alternantherae has the potential to be an effective mycoherbicide for alligatorweed.     

Synergistic interaction between sublethal doses of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> and <Emphasis Type="Italic">Campoletis chlorideae</Emphasis> in managing <Emphasis Type="Italic">Helicoverpa armigera</Emphasis>

Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) is an important solitary larval endoparasitoid of the tomato fruit borer Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in India. The interaction between Bacillus thuringiensis subspecies kurstaki (Btk) HD-1 and C. chlorideae was studied under laboratory condition to explore their compatibility in managing H. armigera. The results had indicated that the growth and development of H. armigera was affected in a dose-dependent manner upon feeding on sublethal doses of Btk HD-1-treated diets. There were no larval survivors in lethal doses of Btk HD-1 (LC₇₀ and LC₉₀). The growth and survival of the parasitoid were normal when the host larvae were fed with sublethal doses or subjected to short time exposure to lethal doses of Btk HD-1. However, the parasitoid offsprings developed slowly and pupal as well as adult period, adult weight and adult emergence rate were reduced significantly if the parasitoid was developing inside a severely Bt intoxicated host larvae. There were no evident differences in longevity of parasitoid adults that were fed on honey solution containing different concentrations of Btk HD-1 as compared to adults fed only on honey solution. This indicates no direct adverse effect of Btk HD-1 on C. chlorideae. Further, the gravid female parasitoid did not discriminate Btk HD-1 intoxicated and normal H. armigera larvae for oviposition. The result implies that spore crystal formulation of Btk HD-1 can be effectively used in a synergistic manner along with existing natural or prereleased population of C. chlorideae in organic farming or as components in biointensive IPM module for managing H. armigera.     

Predator Presence Moves <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> Larvae to Distraction

Displacement of herbivorous insects by the presence of predators on whole plants has rarely been studied. By semi-continuous observations of an externally feeding insect herbivore and a predator, we show how the mere presence of the predator, Geocoris lubra Kirkaldy (Hemiptera: Geocoridae), on a plant can have a strong influence on the movement and behaviors of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae. The presence of predators, as opposed to mortality by predators, influenced the proportion of larvae feeding, resting and implementing avoidance activities. In addition, the proportion of time individual larvae allocated to feeding, resting and dropping off plants was affected when predators were present with and without contact between the two. Predators do more than just reduce numbers of herbivores; they influence feeding, displacement and subsequently the distribution of plant damage.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of North American ginseng (<Emphasis Type="Italic">Panax quinquefolius</Emphasis> L.)

North American ginseng (NAG) (Panax quinquefolius L.) is a medicinally important plant with multiple uses in the natural health product industry. As seed propagation is time-consuming because of the slow growth cycle of the plant, in vitro propagation using a bioreactor system was evaluated as an effective approach to accelerate plant production. An efficient method was developed to multiply nodal explants of NAG using liquid-culture medium and a simple temporary immersion culture vessel. The effects of plant growth regulators, phenolics, and chemical additives (activated charcoal, melatonin, polyvinylpolypyrrolidone, and ascorbic acid) were evaluated on in vitro-grown NAG plants. The highest number (12) of shoots per single node was induced in half-strength Schenk and Hildebrandt basal medium containing 2.5 mg/l kinetin, in which 81% of the cultured nodes responded. In a culture medium with 0.5 mg/l α-naphthalene acetic acid (NAA), roots were induced in 78% of the explants compared to 50% with a medium containing indole-3-acetic acid. All of the resulting plants appeared phenotypically normal, and 93% of the rooted plants were established in the greenhouse. Phenolic production increased significantly (P < 0.05) over a 4-wk culture period with a negative impact on growth and proliferation. Activated charcoal (AC; 50 mg/l) significantly reduced total phenolic content and was the most effective treatment for increasing shoot proliferation. Shoot production increased as the phenolic content of the cultures decreased. The most effective treatment for NAG development from cultured nodal explants in the bioreactor was 2.5 mg/l kinetin, 0.5 mg/l NAA, and 50 mg/l AC in liquid culture medium. This protocol may be useful in providing NAG tissues or plants for a range of ginseng-based natural health products.