马缨丹提取物对黄曲条跳甲成虫的生物活性

测定了马缨丹(Lantana camaraL.)地上部位(茎叶花)的不同溶剂提取物及萃取物对黄曲条跳甲Phyllotreta striolata(Fabricius)成虫的取食忌避、拒食、胃毒和触杀作用。结果表明:处理后48 h,以马缨丹乙醇回流提取物效果最好,其对黄曲条跳甲成虫的取食忌避率达94.94%;非选择性拒食率为85.48%;除正丁醇萃取物对黄曲条跳甲成虫的胃毒作用达到56.67%外,其它处理对黄曲条跳甲成虫的胃毒作用不明显;石油醚萃取物、石油醚冷浸物、乙醇回流物对黄曲条跳甲成虫的触杀作用效果最好,分别为56.67,53.33和53.33%。据实验结果可知马缨丹不同溶剂提取物及萃取物对黄曲条跳甲成虫的生物活性主要表现在对成虫较强的忌避和拒食作用。     

Desiccation and egg viability of the ragwort flea beetle,Longitarsus flavicornis (Coleoptera: Chrysomelidae)

A study was conducted to investigate the effect of desiccation on the survival of eggs of Longitarsus flavicornis. Eclosion of L. flavicornis eggs in laboratory trials decreased with increasing desiccation time between 0 days (93% hatching) and 42 days (no egg hatching) at 50±2% relative humidity and 23±2°C. Probit analysis indicated that 25, 50 and 99% mortality of L. flavicornis eggs occurred after 5.7, 9.3 and 50.4 days desiccation, respectively. Egg development varied between a minimum of 8 days at 7 days desiccation to a maximum of 15 days at 28 days desiccation. Hatching span did not differ between treatments with all eggs hatching within 12 days of each other. A relative humidity of 88–100% was measured under ragwort rosettes in non-drought field conditions. This would be expected to facilitate successful egg eclosion. However, the occurrence of summer drought could be detrimental to egg survival.     

Distribution and abundance of the herringbone leaf-miner,Ophiomyia camarae (Diptera: Agromyzidae) on Lantana camara (Verbenaceae) in selected areas of Swaziland

The distribution and abundance of Ophiomyia camarae was determined in three ecological regions, i.e., highveld, middleveld, and lowveld of Swaziland. Within each region, sites were selected based on Lantana camara L. density, with 10 plants randomly chosen per sampling site. Ten leaves from each shrub were collected and assessed for any damage caused by the herringbone leaf-miner. Relative abundance, based on the number of shrubs damaged by the herringbone leaf-miner, was scored per site. Three lantana varieties were observed during the sampling period. There were significant differences in mean leaf damage due to leaf-miner activity between varieties (P=0.0162), with 46±4.89% leaves of the pale pink variety damaged compared to 23±5.56 and 21±3.53% leaves of the orange and pink varieties, respectively. While there were no restrictions in terms of distribution, the highest levels of O. camarae populations were observed in the middleveld (P=0.0012), suggesting that this region had the most suitable environmental conditions for this natural enemy. Overall, the abundance was significantly different between regions (P=0.006) and months (P=0.000), with April scoring the highest population levels. Based on our observations, the variation in environmental conditions has an influence on the activity of O. camarae, with the middleveld having the most suitable conditions     

Arid-adapted Mexican leafhopper, Barela parvisaccata (Hemiptera: Cicadellidae), unsuitable for biocontrol of Lantana camara (Verbenaceae) in South Africa

A host specificity study conducted in South Africa between 2000 and 2004 showed that the leafhopper, Barela parvisaccata Young, performed as well on some of the indigenous Lippia spp. as on the target weed Lantana camara L. During adult no-choice tests, B. parvisaccata reproduced on eight species of the two closely related genera, Lantana and Lippia. Although B. parvisaccata has a restricted host range, its reproductive performance on the indigenous Lippia scaberrima Sond. during the adult multiple-choice tests was unacceptably high. It was therefore concluded that B. parvisaccata was not sufficiently host-specific to be released against L. camarara in Africa.     

Host specificity of the ragwort flea beetle Longitarsus jacobaeae (Waterhouse) (Coleoptera:Chrysomelidae)

Abstract

The ragwort flea beetle, Longitarsus jacobaeae, was tested for host specificity against representative species of native New Zealand Senecio. Adult feeding and oviposition tests were carried out under quarantine with and without a choice of host plants. Larval development was assessed using potted plants. It was concluded that L. jacobaeae is highly specific to Senecio jacobaea and that it is extremely unlikely to be damaging to native New Zealand Senecio species.     

Effect of herbivory by Teleonemia scrupulosa on the performance of Longitarsus bethae on their shared host,Lantana camara

Herbivory by insects may change the characteristics of nutrients and secondary plant chemicals of the foliage, thereby altering the acceptability and suitability of the plant for oviposition, feeding and development for subsequent herbivores. In the current study, the effect of herbivory by the sap-sucking lace bug, Teleonemia scrupulosa Stäl (Heteroptera: Tingidae), on the suitability of Lantana camara L. (Verbenaceae) for the root-feeding flea beetle, Longitarsus bethae Savini & Escalona (Chrysomelidae: Alticinae), was investigated under laboratory conditions. Preference of adult L. bethae was not influenced by the intensity of feeding damage caused by T. scrupulosa adults. However, high densities of T. scrupulosa nymphs and their feeding damage caused L. bethae adults to emigrate and colonize less infested or uninfested plants. Oviposition by L. bethae was significantly reduced at high densities of T. scrupulosa nymphs. While low infestation of T. scrupulosa had no effect the survival of L. bethae, moderate and high infestations caused significant reduction in percentage survival of L. bethae. The number of T. scrupulosa nymphs was negatively correlated with the percentage survival of L. bethae. Neither the duration of development nor the body size of L. bethae was influenced by the intensity of T. scrupulosa infestation. Overall, undamaged or slightly damaged plants that allowed better survival of L. bethae were often chosen as oviposition sites in preference to those that were highly infested, and on which survival was poor. Although the present study indicates the likelihood of inter-specific competition between L. bethae larvae and T. scrupulosa, this is likely to be mitigated by female flea beetles choosing to oviposit on less infested or uninfested plants in the field.     

Survival of larvae of the ragwort flea beetle, Longitarsus flavicornis (Coleoptera: Chrysomelidae), in water-logged soil

Water-logged soil could be a major factor affecting populations of the ragwort biological control agent, Longitarsus flavicornis, in Australia. Survival of L. flavicornis larvae in potted ragwort plants after inundation with water for up to 264h (11days) was compared to larval survival in control plants not exposed to inundation. Probit analysis indicated that 35.6% mortality of the larval population occurred after 24h inundation and 50.4% after 72h. As high mortality was recorded at periods of inundation known to occur in the field, it is concluded that winter flooding is likely to be detrimental to populations of L. flavicornis.     

Influence of soil texture, moisture, and surface cracks on the performance of a root-feeding flea beetle, Longitarsus bethae (Coleoptera: Chrysomelidae), a biological control agent for Lantana camara (Verbenaceae)

Laboratory studies were conducted to determine the influence of soil texture, moisture and surface cracks on adult preference and survival of the root-feeding flea beetle, Longitarsus bethae Savini and Escalona (Coleoptera: Chrysomelidae), a natural enemy of the weed, Lantana camara L. (Verbenaceae). Adult feeding, oviposition preference, and survival of the immature stages of L. bethae were examined at four soil textures (clayey, silty loam, sandy loam, and sandy soil), three soil moisture levels (low, moderate, and high), and two soil surface conditions (with or without surface cracks). Both soil texture and moisture had no influence on leaf feeding and colonization by adult L. bethae. Soil texture had a significant influence on oviposition, with adults preferring to lay on clayey and sandy soils to silty or sandy loam soils. However, survival to adulthood was significantly higher in clayey soils than in other soil textures. There was a tendency for females to deposit more eggs at greater depth in both clayey and sandy soils than in other soil textures. Although oviposition preference and depth of oviposition were not influenced by soil moisture, survival in moderately moist soils was significantly higher than in other moisture levels. Development of immature stages in high soil moisture levels was significantly slower than in other soil moisture levels. There were no variations in the body size of beetles that emerged from different soil textures and moisture levels. Females laid almost three times more eggs on cracked than on noncracked soils. It is predicted that clayey and moderately moist soils will favor the survival of L. bethae, and under these conditions, damage to the roots is likely to be high. This information will aid in the selection of suitable release sites where L. bethae would be most likely to become established.     

Influence of temperature, photoperiod and humidity on oviposition and egg hatch of the root-feeding flea beetle Longitarsus bethae (Chrysomelidae: Alticinae), a natural enemy of the weed Lantana camara (Verbenaceae)

The root-feeding flea beetle Longitarsus bethae Savini & Escalona, was introduced into South Africa as a candidate biological control agent for the noxious and invasive weed, Lantana camara L. As part of the study to predict the beetles' survival in its new range, the influence of climatic conditions on its egg development and reproductive performance were investigated in the laboratory. The threshold temperature (T degrees) and degree-days (DD) required for egg hatch were determined after exposing the eggs to various constant temperatures (12, 17, 22, 27 and 32 degrees C) in separate growth chambers. The DD required for egg hatch was 178.6, and the temperature threshold required for egg hatch was 11.3 degrees C. Survival of eggs varied from 27 to 56% at 32 and 17 degrees C, respectively, and was optimum between 17 and 25 degrees C. Oviposition was examined under high and low relative humidity (RH) regimes while egg hatch was determined at six RH levels, each maintained in a separate controlled growth chamber set at a constant temperature (25 degrees C). Whilst RH had no influence on oviposition, eggs were highly susceptible to aridity, and continuous exposure to relative humidity below 63% for more than three days was wholly lethal at 25 degrees C. Optimum egg hatch occurred at RH between 85 and 95% for up to 12 days. The effect of day length on oviposition and subsequent egg hatch was investigated under two photoperiod regimes. Neither oviposition nor subsequent egg hatch was influenced by photoperiod. The knowledge obtained will be useful for mass rearing as well as field release programmes for L. bethae.     

Suppression of growth and reproductive capacity of the weed Lantana camara (Verbenaceae) by Ophiomyia camarae (Diptera: Agromyzidae) and Teleonemia scrupulosa (Heteroptera: Tingidae)

An 8-month study was conducted to determine the effect of herbivory by the herringbone leafminer Ophiomyia camarae Spencer (Diptera: Agromyzidae) and the lace bug Teleonemia scrupulosa Stål (Heteroptera: Tingidae) on growth and reproductive capacity of their host plant, Lantana camara L. (Verbenaceae). Ophiomyia camarae adults were released into field cages at two population densities while T. scrupulosa, a widespread and naturalised biocontrol agent in South Africa, colonised and attacked uncaged plants of similar size grown under similar field conditions. At lower initial density, O. camarae reduced stem height, stem diameter, leaf density, flower density and above-ground biomass by 5, 22, 54, 100 and 41%, respectively. At higher initial density of O. camarae, stem height, stem diameter, leaf density, flower density and above-ground biomass were substantially reduced by 19, 28, 73, 99 and 49%, respectively. Teleonemia scrupulosa also reduced stem height, stem diameter, leaf density, flower density and above-ground biomass by 37, 34, 75, 100 and 50%, respectively. The root development was less affected by both O. camarae and T. scrupulosa. Whilst higher densities of O. camarae exerted noticeable herbivore pressure, T. scrupulosa herbivory substantially hampered plant growth and reproductive capacity even at lower population levels. These findings suggest that O. camarae, released in 2001 for the control of lantana, would be effective as part of a complementary guild of biological control agents. The profound effect of herbivory by T. scrupulosa on plant growth and reproductive capacity suggests that it is making a much greater contribution to the biological control of lantana in South Africa than was previously thought.     

Antitermitic effect of the Lantana camara plant on subterranean termites (Isoptera: Rhinotermitidae)

Abstract The insecticidal effects of Lantana camara L. (flowers, leaves, stems and roots) and the soil where lantana had been growing, on foraging activity and survival of the subterranean termites Coptotermes formosanus and Reticulitermes flavipes were examined in a 3-week experiment. The soil in which lantana had been growing had no effect on termite tunneling and survival. Incorporation of chipped fresh lantana leaves and stems into soil had no effect on mortality but caused significant reduction in tunneling. The 5-cm wide barrier of soil with lantana tissue incorporated effectively repelled groups of both species from penetrating the barrier and thus prevented infestation of a piece of wood on the other side of the barrier. C. formosanus was more sensitive in avoiding the barrier than R. flavipes. Leaves, stems and flowers were more repellent than roots. These results provide preliminary evidence that fresh-cut lantana leaves, stems and flowers may have use as additives to garden mulches against termites.     

A pilot project testing the effectiveness of three weed control methods on the removal of Lantana camara in Forty Mile Scrub National Park,Queensland, Australia

Lantana (Lantana camara) poses a serious threat to the biodiversity of the dry rainforest vegetation at Forty Mile Scrub National Park, Queensland, Australia, by outcompeting native species and increasing vulnerability to fire. This pilot study tests the effectiveness of three weed control methods (hand pulling, a glyphosphate‐based foliar spray herbicide and a picloram‐ and triclopyr‐based basal bark herbicide) in removing lantana and their success in reducing lantana fuel loads. The foliar spray herbicide was the most effective in killing lantana, while manual pulling resulted in the largest decrease in fuel height. We suggest that foliar spraying will be most efficient for combating large infestations of lantana, while hand pulling techniques are recommended for creating firebreaks or when minimizing damage to native species is paramount.     

马缨丹乙醇提取物对美洲斑潜蝇种群的控制作用

应用作用因子生命表方法以及在此基础上提出的干扰作用控制指数法评价了马缨丹(LantanacamaraL.)乙醇提取物(干重1g·100mL-1)在美洲斑潜蝇LiriomyzasativaeBlanchard种群控制中的作用。结果表明,马缨丹乙醇提取物对保护菜豆(PhaseolusvagarisL.)免受美洲斑潜蝇为害起着明显的作用。处理区的干扰作用控制指数为0.135,即对美洲斑潜蝇的防治效果可达86.5%。马缨丹乙醇提取物对美洲斑潜蝇寄生性天敌的作用无影响。     

Biology and host range of Ophiomyia camarae, a biological control agent for Lantana camara in South Africa

The herringbone leaf-mining fly, Ophiomyiacamarae Spencer, is a promising candidateagent for the biological control of the alieninvasive weed Lantana camara L. in SouthAfrica. During extensive host-specificity testsinvolving 39 test plant species from 12families, survival to adulthood was restrictedto L. camara, L. trifolia, and fourspecies of the closely-related genus Lippia (Verbenaceae) in no-choice tests. However, survival of the immature stages wassignificantly lower on L. trifolia andthe four Lippia species than on L.camara. In addition, O. camaraedisplayed very strong oviposition preferencefor L. camara during paired-choice tests.This narrow laboratory host range suggests thatO. camarae will not pose any risks tonon-target verbenaceous plants if released inSouth Africa. Permission to release O. camaraeinto South Africa was approved by the regulatoryauthorities in 2001.     

Additions to the mycobiota of the weed Lantana camara (Verbenaceae) in southeastern Brazil

A sequel to the work of systematic surveying the mycobiota of Lantana camara aimed at finding potential biocontrol agents, was carried out during 1995–1996 covering part of its centre of origin in Brazil (state of Minas Gerais). Fifty-eight sampling sites, representing the four main climatic types in the state of Minas Gerais, were surveyed. Additional ad hoc collections were made in the states of Bahia, Espírito Santo, Paraná Rio de Janeiro and São Paulo. Fifteen fungal species were recorded in association with L. camara including the previously undescribed species Phomopsis lantanae-glutinosae sp. nov. Five fungi are also newly recorded on this host in Brazil: Cercospora lantanicola Corynespora cassiicola Meliola ambigua Mycovellosiella lantaniphila and Phomopsis lantanae. The following fungi, previously recorded on L. camara in Brazil, are recorded here for the first time in Minas Gerais: Dendryphielia aspera Micropustulomyces mucilaginosus Mycovellosiella lantanae Pseudocercospora guianensis and Puccinia lantanae.     

Parent-offspring conflicts, "optimal bad motherhood" and the "mother knows best" principles in insect herbivores colonizing novel host plants

SPECIALIZATION OF INSECT HERBIVORES TO ONE OR A FEW HOST PLANTS STIMULATED THE DEVELOPMENT OF TWO HYPOTHESES ON HOW NATURAL SELECTION SHOULD SHAPE OVIPOSITION PREFERENCES: The "mother knows best" principle suggests that females prefer to oviposit on hosts that increase offspring survival. The "optimal bad motherhood" principle predicts that females prefer to oviposit on hosts that increase their own longevity. In insects colonizing novel host plants, current theory predicts that initial preferences of insect herbivores should be maladaptive, leading to ecological traps. Ecological trap theory does not take into account the fact that insect lineages frequently switch hosts at both ecological and evolutionary time scales. Therefore, the behavior of insect herbivores facing novel hosts is also shaped by natural selection. Using a study system in which four Cephaloleia beetles are currently expanding their diets from native to exotic plants in the order Zingiberales, we determined if initial oviposition preferences are conservative, maladaptive, or follow the patterns predicted by the "mother knows best" or the "optimal bad motherhood" principles. Interactions with novel hosts generated parent-offspring conflicts. Larval survival was higher on native hosts. However, adult generally lived longer on novel hosts. In Cephaloleia beetles, oviposition preferences are usually associated with hosts that increase larval survival, female fecundity, and population growth. In most cases, Cephaloleia oviposition preferences follow the expectations of the "mothers knows best" principle.     

Suitability of common weed species as host plants for the potato leafhopper,Empoasca fabae

The suitability of 13 weed species as host plants for the potato leafhopper,Empoasca fabae (Harris) (Homoptera: Cicadellidae) was compared to alfalfa,Medicago sativa L., and broad bean,Vicia faba L., in laboratory and greenhouse tests. Nymphs developed and adults reproduced on five of the weeds: smartweed (Polygonum pensylvanicum L.), pigweed (Amaranthus retroflexus L.), shepherdspurse (Capsella bursa-pastoris (L.) Medic.), dandelion (Taraxacum officinale Weber), and carpetweed (Mollugo verticillata L.). Adults survived and oviposited on all tested weeds, suggesting that nymph survival was the limiting factor in host suitability. Yellow nutsedge (Cyperus esculentus L.), crabgrass (Digitaria sanguinalis (L.) Scop.), and foxtail (Setaria faberi Herrm.) were least suitable for adult and nymph survival. Large nymphs (instar III–IV) were able to complete development on weed species that did not support small nymph (instar I–II) development to adulthood. Densities of nymphs on weeds from alfalfa fields as well as the laboratory studies suggested that the weed species are less suitable as hosts and thus weeds probably do not affect population increases of potato leafhopper within weedy alfalfa fields by serving as hosts. Weeds may however, interact with the crop to alter leafhopper colonization, dispersal, and/or reproduction. In addition, since some broadleaf weeds are suitable hosts, the leafhopper may have a secondary beneficial role for biological weed control. These interactions should be considered when evaluating pest management practices.

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Eignung häufiger Unkrautarten als Wirte vonEmpoasca fabae

Zusammenfassung Der Wirtskreis derEmpoasca fabae (Harris) (Homoptera: Cicadellidae) wurde im Labor und im Freiland untersucht. Dreizehn Unkrautarten, wie auch Luzerne (Medicago sativa L.) undVicia faba L., wurden im Laborversuchen geprüft. Die Entwicklung der Nymphen und die Eiablage setzten auf fünf Unkrautarten fort: aufPolygonum pensylvanicum L.,Amaranthus retroflexus L.,Capsella bursa-pastoris (L.) Medic.,Taraxacum officinale Weber undMollugo verticillata L. Die Eiablage und das Weiterleben der Imagines geht auf allen untersuchten Unkräutern weiter. Dies weist darauf hin, dass die Lebensdauer der Nymphen die Eignung der Wirte begrenzt. Das Weiterleben der Imagines und der Nymphen waren aufCyperus esculentus L.,Digitaria sanguinalis (L.) Scop. undSetaria faberi Herrm. am stärksten verkürzt. Die Altnymphentwicklung (3. und 4. Stadien) bis zur Imago war auf Unkräutern gewährleistet, dagegen erfolgte die Jungnymphentwicklung (1. und 2. Stadien) bis zur Imago nicht. Populationsproben von Luzerne im Freiland, wie auch die Ergebnisse der Laboruntersuchungen, zeigten, dass Unkräuter nicht im Wirtskreis der Nymphen vonE. fabae sind und dass Unkräuter in Luzernefeldern keinen Einfluss auf die Populationszunahme in solcher Feldern haben. Unkräuter in Luzerne dürften aber die Kolonisierung, Verteilung der Population im Feld wie auch das Vermehrungspotential vonE. fabae verändern. Weil einige Unkräuter Wirte der Imago vonE. fabae sind, können sie als Ausweichpflanzen dienen, wenn die Luzerne, z.BB. nach dem Schnitt, für das Ueberleben der Zikaden ungeeignet ist.

     

Evaluation of Napier grass (Pennisetum purpureum) varieties for use as trap plants for the management of African stemborer (Busseola fusca) in a push–pull strategy

We evaluated eight Napier grass [Pennisetum purpureum Schumach (Poaceae)] varieties, used in various parts of eastern Africa as fodder, for their potential role as trap plants in the management of the African stemborer, Busseola fusca Füller (Lepidoptera: Noctuidae) through a push–pull strategy. Oviposition preference, larval orientation, settling, arrest and dispersal, feeding, mortality and survival, and development were determined for each of these varieties under laboratory and screen house conditions. Two‐choice tests showed that only two of the varieties tested (cv. Bana and cv. Uganda Hairless) were preferentially chosen by gravid female moths for oviposition over a susceptible maize variety, cv. Western Hybrid 502. Larval preference was, however, highly variable. Larval feeding by first instars on the maize leaves was more intense and significantly more than on leaves of all the Napier grass varieties evaluated. Food consumed and amounts assimilated by the third instars over a 24‐h period were not different among larvae fed on stems of maize and those fed on stems of the various Napier grass varieties. Larval survival was significantly lower on all the Napier grass varieties (below 3%) than on maize (about 44%). Similarly, larval development was about 2–3 weeks longer on majority of the Napier grass varieties. It was concluded that cv. Bana had potential for use as a trap plant in the management of B. fusca because it was more preferred by the moths for oviposition, equally preferred as maize by the larvae for orientation, settling, and arrest, and allowed minimal survival of the larvae. It can thus be used with such ‘push’ plants as Desmodium spp. (Fabaceae) in a ‘push–pull’ strategy, but the effectiveness of such a strategy would strictly depend on proper establishment and management of these companion plants.     

Adaptive change and conservatism in host specificity in two local populations of the thistle-feeding ladybird beetle Epilachna niponica

We investigated geographic differences in the host specificity of Epilachna niponica Lewis (Coleoptera: Coccinellidae). The Yuwaku population feeds mainly on Cirsium matsumurae Nakai (Asteraceae) and secondarily on Cirsrium kagamontanum Nakai. The Asiu population, located 150 km away from the Yuwaku, feeds exclusively on C. ashiuense Yokoyama et T. Shimizu. Under laboratory conditions, we examined the differences between the two populations in adult feeding acceptance, adult feeding preference, and larval performance, using several closely related thistle species and varieties, including their native hosts. In the Asiu population, adult beetles clearly avoided the host of the Yuwaku population, C. kagamontanum, and no larvae were able to complete their development, whereas in the Yuwaku population, adults accepted and even preferred it to some other thistle species, and about 10% of first instar larvae became adults. This indicates that the Yuwaku population evolved its feeding preference and physiological adaptation to C. kagamontanum through a utilization of this low‐ranked host under natural conditions. Apart from C. kagamontanum, the two populations showed a similar host susceptibility pattern, indicating that this ladybird beetle has a conserved hierarchy in feeding preference and growth performance. We also observed adult leaf choice behavior when given different thistle species, and found that difference in biting rate after palpation determined the leaf areas consumed, implying that factors on the leaf surface played an important role in the choice.