首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The ornamental hybrid shrub, Lantana camara L. (lantana), is a serious environmental weed and has been targeted for biological control in South Africa since 1961. The established biocontrol agents cause insufficient levels of damage and additional natural enemies are required to reduce the invasiveness of this weed. The lantana mirid, Falconia intermedia (Distant), is a promising new agent that was imported from the Caribbean for life history and host-range studies. The nymphs and adults are leaf-suckers that cause chlorotic speckling, which reduces the photosynthetic capacity of the plant. Biological studies indicate that F. intermedia has considerable biocontrol potential, in that it has a high intrinsic rate of increase, the potential for multiple generations a year, highly mobile adults, and a high level of damage per individual. Host-specificity trials indicated that the lantana mirid has a narrow host range, with L. camara being the most suitable host, but several indigenous African species in the closely related genus Lippia are suitable alternative host plants. Under multiple-choice conditions, adults showed a significant and strong oviposition preference for L. camara over the Lippia species. A risk assessment of potential nontarget effects indicated that three Lippia species could sustain damage levels in the field. The relatively low probability of damage to indigenous species was considered a justified trade-off for the potentially marked impact on L. camara. The regulatory authorities accepted the results of this study and F. intermedia was released against L. camara in South Africa in April 1999.  相似文献   

2.
Biological control of invasive saltcedars (Tamarix spp.) in the western U.S. by exotic tamarisk leaf beetles, Diorhabda spp., first released in 2001 after 15 years of development, has been successful. In Texas, beetles from Crete, Greece were first released in 2004 and are providing control. However, adults alight, feed and oviposit on athel (Tamarix aphylla), an evergreen tree used for shade and as a windbreak in the southwestern U.S. and México, and occasionally feed on native Frankenia spp. plants. The ability of tamarisk beetles to establish on these potential field hosts was investigated in the field. In no-choice tests in bagged branches, beetle species from Crete and Sfax, Tunisia produced 30–45% as many egg masses and 40–60% as many larvae on athel as on saltcedar. In uncaged choice tests in south Texas, adult, egg mass and larval densities were 10-fold higher on saltcedar than on adjacent athel trees after 2 weeks, and damage by the beetles was 2- to 10-fold greater on saltcedar. At a site near Big Spring, in west-central Texas, adults, egg masses and 1st and 2nd instar larvae were 2- to 8-fold more abundant on saltcedar than on athel planted within a mature saltcedar stand being defoliated by Crete beetles, and beetles were 200-fold or less abundant or not found at all on Frankenia. At a site near Lovelock, Nevada, damage by beetles of a species collected from Fukang, China was 12–78% higher on saltcedar than on athel planted among mature saltcedar trees undergoing defoliation. The results demonstrate that 50–90% reduced oviposition on athel and beetle dispersal patterns within resident saltcedar limit the ability of Diorhabda spp. to establish populations and have impact on athel in the field.  相似文献   

3.
Azolla filiculoides (red waterfern) is a small, floating fern native to South America, that has invaded aquatic habitats, predominantly water resevoirs in southern Africa. A frond-feeding weevil, Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae), was imported from Florida, USA, and released as a biological control agent against this weed in South Africa at the end of 1997. To date, 24,700 weevils have been released, which has resulted in local extinction of red waterfern at 81% of the 112 release sites. The weevil has not failed to control a single site. Several sites were, however, lost due to flooding or drainage of dams. The surface area of weed controlled totalled 203.5 ha. On average, A. filiculoides was controlled in infested sites in 6.9 (±4.3) months. The weed recolonized at 22 of the sites (through either spore germination or dispersal by waterfowl), but the weevils subsequently spread to all of these sites and successfully caused local extinction of the weed at 18 of the sites. Five years after the release of the weevil, the weed no longer poses a threat to aquatic systems in southern Africa. In comparison to other biological control programs of aquatic weeds, the program against A. filiculoides in southern Africa ranks among the most successful cases anywhere in the world.  相似文献   

4.
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.  相似文献   

5.
The Madagascan endemic, Bryophyllum delagoense (Crassulaceae), is a major weed in Queensland, Australia. Despite having first been recorded in Australia in the 1940s, it is far more invasive there than on the African mainland where it was introduced more than 170 years ago. This may be due to a number of factors, one of which could be the occurrence of new natural enemy associations in southern Africa. Among the insects of crassulaceous plants that have extended their host ranges, a stem-boring weevil, Alcidodes sedi, was studied to elucidate its status as a natural enemy of B. delagoense in southern Africa and as a candidate biological control agent for introduction to Australia. Laboratory studies indicated that damage inflicted by adult and larval feeding caused significant reductions in stem length and number of leaves. Preliminary host-range trials revealed that A. sedi can complete its development on other species in the Crassulaceae, including most of the introduced Bryophyllum species and some Kalanchoe species native to South Africa. Despite the oligophagous nature of A. sedi and the fact that it can complete its development on a number of ornamental species in the Crassulaceae, it should be considered a potential biological control agent in Australia. All of the native Crassulaceae in Australia are in the genus Crassula, most of which are very small and therefore unlikely to support the development of a large weevil like A. sedi. However, additional host-range trials will have to be undertaken in Australia to determine whether the weevil can be considered safe for release.  相似文献   

6.
The peacock moraeas are South African geophytes withIris-like flowers that are characterized by broad outer tepals with iridescent spots. Three of the seven species were studied and found to be exclusively visited and pollinated by beetles. The primary pollinators were hopliine (Scarabaeidae) beetles in the generaPeritrichia, Monochelus, Anisonyx andAnisochelus. These beetles visit flowers for nectar, pollen and mating.Peritrichia rufotibialis was the primary pollinator ofMoraea villosa, P. abdominalis was the primary pollinator ofM. tulbaghensis, whileMonochelus sp. nov. was the primary pollinator of the third species,M. neopavonia. High levels of fruit set attest to the effectiveness of these beetles as pollinators. Average fruit set ranged from 83.5 ± 34.8% (M. villosa) to 97.2 ± 11.6% (M. tulbaghensis). Average seed set in the various populations was more variable, but was also quite high, ranging from 77.3 ± 40.8 (M. villosa) to 342.2 ± 115.0 (M. neopavonia) seeds per capsule. Although hopliine beetles are abundant and diverse in southern Africa and commonly visit flowers, this is the first well-documented report of pollination by these beetles.  相似文献   

7.
Summary The establishment in South Africa of a florivorous, apionid weevil, Trichapion lativentre, on Sesbania punicea, a leguminous weed of South American origin, has reduced seed production of the plants by >98%. Surveys of the age structure and density of plants in infestations of S. punicea throughout South Africa have shown that the rate of recruitment of seedlings has drastically declined within a few years in many areas, due to the weevils. However, there has unexpectedly not been a corresponding decline in the density of mature plants in extant infestations of S. punicea. In spite of this, T. lativentre has curtailed the rate of spread of the weed into uninvaded habitats and has impeded reinvasion into areas cleared of infestations by mechanical means or by another complimentary biocontrol agent.  相似文献   

8.
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.  相似文献   

9.
Mustard green manures or seed meal high in glucosinolates, which produce a natural biofumigant upon incorporation into the soil, form an alternative to synthetic fumigants. However, the non-target impacts of these biofumigants in the field are unclear. We examined the effectiveness of soil incorporation of Brassica carinata seed meal both in controlling the plant-parasitic Columbia root-knot nematode (Meloidogyne chitwoodi), and on the biological control exerted by the entomopathogenic nematodes Steinernema feltiae and Steinernema riobrave on root-knot nematodes and the Colorado potato beetle (Leptinotarsa decemlineata). Singly, both the seed meal and Steinernema spp. reduced root-knot nematode damage to potato tubers and increased marketable tuber yields. However, there was a negative interaction between the two bioagents such that their combination did not further improve suppression of plant-parasitic nematodes. Thus, mustard seed meal applications harmful to the target root-knot nematode also disrupted the ability of Steinernema spp. to act as biocontrol agents. Further, we observed modest disruption of the biological control of potato beetles following biofumigation. But, the potato beetles were less likely to lay eggs on potato plants grown in mustard-amended soil, suggesting a counteracting benefit of mustard application. Multiple, complementary controls must be integrated to replace the very effective pest suppression typical of synthetic soil fumigants. Our study suggests significant interference between biofumigation and biocontrol agents in the soil, presenting challenges in combining these two environmentally friendly approaches to managing plant-parasitic nematodes and other pests.  相似文献   

10.
Mixed populations of Aphthona lacertosa and Aphthona czwalinae were released at more than 50 locations in Alberta in 1997. Two and 3 years post-release, beetle populations were primarily A. lacertosa, with A. czwalinae forming less than 0.5% of the sampled populations. Beetle densities were moderate (10–70 beetles per m2) or high (>70 beetles per m2) at 14% and more than 60% of the sampled sites in 1999 and 2000, respectively. Larger beetles had greater instantaneous egg loads (r2=0.424,P=0.003). In 2000, the largest beetles were found at moderate density sites and there was a significant negative relationship between beetle size and the time taken to accumulate a degree day threshold of 1230 (for females: r2=0.678,P=0.001). Sites with the most rapid accumulation of degree days have the greatest potential for beetle population growth based on potential fecundity. Changes in leafy spurge percent cover, stem density, and canopy height from 1997 to 2000 were assessed across sites with low (<10 beetles per m2), moderate, and high beetle densities in 2000. Sites with high beetle densities had significantly greater reductions of leafy spurge within 5 m of the release point than sites with low beetle densities (P<0.017). Damage caused by the beetles at high-density sites was often visible as a halo-shaped patch of dead leafy spurge stems. The significant overall reduction of leafy spurge within release patches makes A. lacertosa a promising biocontrol agent for leafy spurge in Alberta.  相似文献   

11.
The genus Diabrotica (Coleoptera: Chrysomelidae) includes a great number of pest species, including some of the most important crops pests of the Americas. However, only five parasitoid species have been recorded for it. The parasitoid Celatoria bosqi Blanchard was the first parasitoid described from Diabrotica spp. in South America, where substantial parasitism has been observed. C. bosqi has been collected almost throughout the South American distribution of its main host, Diabrotica speciosa (Germar), in an area that includes temperate and tropical lowlands, and semiarid to humid highlands. Three Diabrotica species were found to host the parasitoid, D. speciosa (Germar), Hystiopsis sp., and Diabrotica viridula (F.), with a total parasitism of 2.60, 5.55, and <0.02%, respectively. Laboratory experiments with field beetles and puparia, reared in the laboratory, indicate that C. bosqi overwinters obligatorily in overwintering adult host beetles, remaining quiescent in its live host below developmental temperatures. Based on the known climatic range of C. bosqi, and its requirement of adult overwintering hosts, a potential distribution in North America is projected.  相似文献   

12.
Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) was introduced as an ornamental in South Africa, but is fast becoming an important invasive plant in many areas. It is difficult to control the plant chemically and mechanically. The first biocontrol agent, the chrysomelid Charidotis auroguttata (Boheman), has been released. It established at some release sites, but numbers have so far remained low. Additional biocontrol agents were sought to augment C. auroguttata. The potential host ranges of two foliage feeding lace bugs, Carvalhotingis visenda (Drake and Hambleton) and C. hollandi (Drake) (Hemiptera: Tingidae) were evaluated on the basis of nymphal no-choice and adult multi-choice tests involving 23 plant species in 11 families. In no-choice tests, nymphs of both species were able to survive and complete development on M. unguis-cati only, and adults of both species only fed and oviposited on M. unguis-cati during the adult multi-choice tests. Host specificity tests thus confirm that the tingids are highly host specific biocontrol agents, and will not pose risk to any non-target plants in South Africa. A study to determine the potential impact of C. hollandi nymphal feeding on M. unguis-cati showed a significant decrease in the chlorophyll contents of leaves when compared to those of control plants. These studies indicate that, once released, the two lace bug species could contribute significantly to the biological control of M. unguis-cati in South Africa.  相似文献   

13.
Many Cola plant species are endemic to West and Central Africa. Cola acuminata and Cola nitida are used as masticatory when fresh, while the dried nuts are used for beverages and pharmaceutical purposes in Europe and North America. Garcinia kola seeds, that serve as a substitute for the true kola nuts, are used in African traditional medicine for the treatment of various diseases, including colic, headache and liver cirrhosis. Seeds extracts of G. kola are also known for their anti-inflammatory, antimicrobial and antiviral properties. To gain information on the chemical properties of the kolas, we have isolated and analyzed cell wall polysaccharides, arabinogalactan-proteins and phenolic substances from the seeds of the three kola species. The sugar composition of cell wall material of C. acuminata, C. nitida and G. kola revealed that Gal (up to 30%), Ara, GalA and Glc as the predominant monosaccharides, representing approximately 90% by mol of the total hydrolysable sugar present in this material. In Ammonium oxalate cell wall fraction, GalA was found to be the major sugar present in all kola species. In the alkali-soluble fraction, there were significant differences in the level of Glc and Gal. The level of Glc was high in C. acuminata and C. nitida while the level of Gal and Xyl were high in C. nitida and G. cola. Isolation and quantification of arabinogalactan-proteins demonstrate that G. kola seeds contained four to eight times more of these proteoglycans than the seeds of the other two species. Finally, analysis of soluble phenolic substances shows that caffeine and catechin were largely represented in C. acumina and C. nitida seeds, with caffeine accounting for 50% of all soluble phenolics. These findings indicate that the three Kola seeds are highly enriched in pectins and proteoglycans and that C. acuminata and C. nitida can be used as a possible source of caffeine and catechin.  相似文献   

14.
Experimental studies can be useful tools to test plant responses to herbivory and to quantify the impact of potential biological control agents prior to their release. We evaluated the per-capita effect of Ceutorhynchus alliariae and C. roberti, two stem-boring weevils currently being investigated as potential biological control agents for garlic mustard, Alliaria petiolata, in North America. Weevils were released at three different densities in individual and mixed-species treatments onto potted plants of A. petiolata. Damage by C. roberti alone and by both weevils combined caused an increase in the numbers of inflorescences produced per plant. Although plants could compensate for low levels of damage, moderate to high levels of damage by both C. alliariae and C. roberti, individually and in combination, caused a decrease in plant height and a reduction in seed output per plant. The damage inflicted by both weevil species is similar so the overall impact of both species combined can be predicted by summing the impact of each species alone. Provided they are sufficiently host specific, both weevils could be released as biocontrol agents. Because reduced seed production is necessary to suppress A. petiolata populations, both species have the potential to contribute to control of A. petiolata in North America.  相似文献   

15.
Tropical soda apple (Solanum viarum Dunal (Solanaceae) is a South American invasive plant of rangelands, pastures and natural areas in Florida. A chrysomelid beetle from South America, Gratiana boliviana Spaeth, has been released at >300 locations in Florida for biological control of tropical soda apple since 2003. Tropical soda apple is a host of several plant viruses, including the newly described tropical soda apple mosaic virus (TSAMV). We investigated the influence of TSAMV infection of tropical soda apple plants on developmental time, leaf tissue consumption, longevity, fecundity, and feeding preference of G. boliviana, and also tested transmission of the virus by the beetle. Developmental time was approximately 10% slower, and adults consumed only about 50% as much leaf tissue, for beetles fed on infected plants compared to uninfected plants. Longevity did not differ between females reared on infected and uninfected plants, but females fed on uninfected plants produced 71% more eggs than those fed on infected plants. Adult G. boliviana preferentially fed on uninfected plants when given a choice. There was no evidence of TSAMV transmission by G. boliviana. The potential impacts of TSAMV infection on the effectiveness of G. boliviana as a biological control agent are discussed.  相似文献   

16.
Approximately one-fourth of the more than 900 world-wide distributed Salvia species (Lamiaceae) is ornithophilous. With few exceptions they occur in the New World, being predominantly pollinated by hummingbirds. In the Old World only Salvia africana-lutea and the recently described Salvia thermarum, both from the Cape Province of South Africa, were observed to be pollinated by sunbirds and white-eyes. Among the 23 South African Salvia species Salvia lanceolata is a further candidate for being bird pollinated. For the first time we describe and illustrate its pollination by Nectarinia chalybea and Zosterops pallidus. We compare the ornithophilous syndrome of the three mentioned Salvia species and relate them to the morphological fitting of the most common nectarivorous birds of the Southwestern Cape (Cape peninsula to Worcester). We conclude that each of the birds could act as a pollinator and that the three co-occurring Salvia species are not mechanically isolated from each other. The degree of specialisation towards bird pollination, possible hybridisation events and evolution of bird pollination in South African Salvia species are discussed.  相似文献   

17.
The cassava green mite (CGM), Mononychellus tanajoa, a native of South America was accidentally introduced into Africa where it causes serious crop losses. The possibility of introducing classical biological agents from the native home of CGM into Africa was investigated. Thus, we conducted a series of laboratory assays of the native fungal pathogens, Neozygites tanajoae from Brazil and Neozygites floridana from Colombia and Brazil, and compared them with N. tanajoae isolates from Benin. Infectivity of both fungal species, was assayed against the twospotted spider mite, Tetranychus urticae, and against the red mite, Oligonychus gossypii. Pathogenicity against CGM and host range studies were conducted by transferring adult females of each mite species to leaf discs containing sporulated cadavers with a halo of conidia of each fungal isolate. All isolates caused some degree of infectivity to CGM. None of the isolates of N. floridana and N. tanajoae tested were pathogenic to O. gossypii, and only two isolates infected T. urticae. Most isolates from Brazil were highly virulent and infected only CGM. Sixteen N. tanajoae isolates caused more than 89% mortality and more than 62% of the CGM became mummified. A mummified CGM is characteristically a swollen, brown fungus-killed mite that has great potential to produce conidia. However, high mortality was not always associated with high mummification. The median mummification time ranged from 4.4 to 6.7 days. Five Brazilian isolates caused >75% mummification with a median mummification time <5 days. Isolates that cause high mummification in a short period of time would be more likely to cause epizootics and to establish in the new environment. Therefore, these isolates would be the best candidates for introduction to Africa.  相似文献   

18.
Cesariella graeca gen. sp. nov. is described to accommodate a new species of the Laboulbeniales (Fungi, Ascomycota) parasitic on the endogean ground beetles Reicheadella aetolica and R. bischoffi (Coleoptera, Carabidae) from Greece. Cesariella is distinguished from the allied genus Laboulbenia by the presence of two cells borne on the inner side of cell III, and by the presence of a conspicuous remnant of the spore apex protruding laterally near the base of the appendage.  相似文献   

19.
We examined the Chaetocercus and Lophornis holdings of 21 European, US and South American avian collections. Only skin specimens with exact (to the year) collecting dates and reliable locality data on their labels, which could be checked personally, were analysed. We located 466 Chaetocercus and 373 Lophornis specimens collected between the years 1859 and 1999. The vast majority of these records are old ones, dated between 1880 and 1960: 93% of the Chaetocercus and 82% of the Lophornis study skins. Less than 1% of all specimens was obtained after 1990. Potential explanations for our findings, such as declining population levels of these hummingbird genera, historically changing collecting activities regarding commercial dealers and collecting techniques, and legal collecting restrictions are discussed. Our findings reflect a general trend of decreasing collecting activities worldwide.Communicated by F. Bairlein  相似文献   

20.
Variability in timing of the reproductive stages of Scotch broom (Cytisus scoparius) may influence synchronization and establishment of the broom seed beetle (Bruchidius villosus), a biological control agent. A sampling scheme was devised to compare the phenologies of Scotch broom at different sites in the same season and in different seasons at the same site. The synchrony of the broom seed beetle's life stages with those of the host plant was also determined. The phenology of Scotch broom varied only slightly from season to season at Lincoln, but could vary considerably between sites in the same season. At both sites where it is established, the broom seed beetle was synchronized with its host; adult beetles were present throughout the flowering period. Eggs were found on suitable green pods. The broom seed beetle appears capable of adapting to the phenology of its host and has the potential to be an effective agent for Scotch broom. Variability in phenology of the reproductive stages of Scotch broom, even at nearby sites, must be taken into account by practitioners of biological control when releasing broom seed beetles and later when sampling beetles to determine establishment.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号