Biology of a buprestid beetleSphenoptera clarescens [Col.: Buprestidae], from skeleton weed,Chondrilla juncea

Investigations carried out in Iran, to discover biological control agents for skeleton weed (Chondrilla juncea L.), showed that the buprestid,Sphenoptera clarescens Kerr, was one of the insects highly damaging to the weed. The larvae of this beetle were active throughout theChondrilla season and fed mainly on the rootstocks, causing a progressive decline in naturalChondrilla populations. The host range of the beetle was examined in the field and in the glasshouse, and it was demonstrated thatS. clarescens occurs on and attacks severalCompositae related toC. juncea. As lettuce,Lactuca sativa L., and endive,Cichorium endivia L. could have been at risk in Australia, studies were discontinued.     

Chemistry and biological activities of Calceolaria spp. (Calceolariaceae: scrophulariaceae)

Calceolaria spp. is regarded both as a notorious weed and a popular ornamental garden plant and have medicinal application. Some taxa of the America distributed Calceolaria genus are toxic to insects and its effect has been associated with the presence of diterpenes, triterpenes and naphthoquinones. However, Calceolaria spp. also produces a number of flavonoids and phenylpropanoids that have been shown to possess interesting biological activities. All these aspects are considered in this review to allow an evaluation of the potential for utilization of the large biodiversity of Calceolaria available. The phytochemistry of many members of the Calceolaria genus is included.     

The attractiveness of odorous esterified fatty acids to the potential biocontrol agent,Altica cyanea

The fatty acid composition of foliar buds, young, mature, and senescent leaves, and stem parts of the rice-field weed, Ludwigia adscendens L. (Onagraceae) was analyzed by thin layer chromatography and gas chromatography flame ionization detection. The analysis of fatty acid composition revealed that saturated fatty acids (i.e., C14:0, C16:0, and C18:0) were prevailing compounds among the all weed parts except senescent leaves where C18:1 was predominant. The esterified fatty acids isolated from different weed parts over the range of 10–100 μg/ml followed by individual synthetic esterified fatty acids that were identified from the esterified extracts of different weed parts, and a mixture of synthetic esterified fatty acids except esterified eicosenoic acid and docosahexaenoic acid were applied to identify their role as a chemical cue for a potential biocontrol agent, Altica cyanea (Weber) (Coleoptera: Chrysomelidae) in a Y-tube olfactometer under laboratory conditions. In this bioassay, the esterified fatty acids from mature leaves and stem parts of this weed attracted A. cyanea at 20–100 μg/ml and at 80 μg/ml concentrations, respectively. Clear attraction was recorded by female A. cyanea insects in the mixture of synthetic esterified fatty acids at 60, 80, and 100 μg/ml concentrations. It is thus concluded that A. cyanea rely on an effective proportion of esterified fatty acids as an olfactory cue for attraction.     

The molecular basis of host plant selection in Melaleuca quinquenervia by a successful biological control agent

Melaleuca quinquenervia (Cav) S.T. Blake (broadleaf paperbark) is an Australian tree that has become a serious weed in many places around the world. Two insects Oxyops vitiosa (the melaleuca weevil), and Boreioglycaspis melaleucae (the melaleuca psyllid), which were introduced to Florida as part of a biological control programme, have been very effective in reducing survival and reproduction of this weed. There are two terpene chemotypes of M. quinquenervia; one rich in the sesquiterpene E-nerolidol whereas the other is rich in viridiflorol. Viridiflorol is a strong feeding deterrent for the melaleuca weevil and retards larval development. The larvae therefore avoid the viridiflorol-rich chemotype, in contrast, female melaleuca psyllids prefer to oviposit on these leaves. To identify the molecular basis of these preferences, we isolated and characterised two terpene synthases from the viridiflorol-rich chemotype, both of which utilise farnesyl pyrophosphate and have the same product profile. Chemotypic variation in terpenes in M. quinquenervia is under strong genetic control and the reproductive potential of each chemotype is limited by a different insect. These insects could, therefore, be selective agents for the maintenance of chemotypic variation in M. quinquenervia.     

Efficacité des ennemis naturels deLantana camara à Guam : évaluation locale et saisonnière

As part of a continuing effort to eliminate or, at least, reduceLantana camara L., a weed commonly found in Guam, biweekly surveys were conducted over a four and a halfyear period to determine the effectiveness of the weed’s natural enemies in reducing plant vigor and viable seed numbers. A total of eight biocontrol agents were monitored. The leaf damaging insects were the hispine beetle,Uroplata girardi Pic. (Col.: Chrysomelidae), the tingid bug,Teleonemia scrupulosa Stål (Hem.: Tingidae), the leafminer fly,Calycomyza lantanae Frick (Dip.: Agromyzidae) and the noctuid moth,Hypena strigata (F.) (Lep: Noctuidae). The moths,Lantanophaga pusillidactyla (Walker) (Lep.: Pterophoridae),Epinotia lantana (Busck) (Lep.: Tortricidae) andAdoxopheyes melia Clarke (Lep.: Tortricidae) andT. scrupulosa were the flower damaging insects.E. lantana and the seedfly,Ophiomyia lantanae (Froggatt) (Dip.: Agromyzidae) accounted for berry losses. An empirical biocontrol model was fitted to the observed data. The model estimated that the eight biocontrol agents prevented the production of or damaged 225.9 berries per square meter per biweekly observation period. Observed production was only 96.1 undamaged berries per square meter per observation period. Thus, the biocontrol agents were reducing potential berry production by 70.1 percent. The biocontrol model was also used to estimate the individual contributions of the eight agents to the overall control ofL. camara on Guam     

Host range tests reveal Paectes longiformis is not a suitable biological control agent for the invasive plant Schinus terebinthifolia

The most critical step during a weed biological control program is determination of a candidate agent’s host range. Despite rigorous protocols and extensive testing, there are still concerns over potential non-target effects following field releases. With the objective to improve risk assessment in biological control, no-choice and choice testing followed by a multiple generation study were conducted on the leaf-defoliator, Paectes longiformis Pogue (Lepidoptera: Euteliidae). This moth is being investigated as a biological control agent of Schinus terebinthifolia Raddi (Sapindales: Anacardiaceae), which is one of the worst invasive plant species in Florida, USA. Results from no-choice testing showed higher larval survival on S. terebinthifolia (48 %) and its close relative Schinus molle L. (47 %), whereas lower survival was obtained on six non-target species (<25 %). When given a choice, P. longiformis females preferred to lay eggs on the target weed, but oviposition also occurred on four non-target species. An improved performance on the native Rhus aromatica Aiton was found when insects were reared exclusively on this non-target species for one or two generations. Results from host range testing suggest that this moth is oligophagous, but has a preference for the target weed. Non-target effects found during multiple generation studies indicate that P. longiformis should not be considered as a biological control agent of S. terebinthifolia.     

Non-crop vegetation associated with chili pepper agroecosystems promote the abundance and survival of aphid predators

Habitat manipulation has long been used as strategy to enhance beneficial insects in agroecosystems. Non-crop weed strips have the potential of supplying food resources to natural enemies, even when pest densities are low. However, in tropical agroecosystems there is a paucity of information pertaining to the resources provided by non-crop weeds and their interactions with natural enemies. In this study we evaluated (a) whether weeds within chili pepper fields affect the diversity and abundance of aphidophagous species; (b) whether there are direct interactions between weeds and aphidophagous arthropods; and (c) the importance of weed floral resources for survival of a native and exotic coccinellid in chili pepper agroecosystems. In the field, aphidophagous arthropods were dominated by Coccinellidae, Syrphidae, Anthocoridae, Neuroptera and Araneae, and these natural enemies were readily observed preying on aphids, feeding on flowers or extrafloral nectaries, and using plant structures for oviposition and/or protection. Survival of native Cycloneda sanguinea (Coleoptera: Coccinellidae) differed between plant species, with significantly greater survival on Ageratum conyzoides and Bidens pilosa. However, no evidence was gathered to suggest that weed floral resources provided any nutritional benefit to the exotic Harmonia axyridis (Coleoptera: Coccinellidae). This research has provided evidence that naturally growing weeds in chili pepper agroecosystems can affect aphid natural enemy abundance and survival, highlighting the need for further research to fully characterize the structure and function of plant resources in these and other tropical agroecosystems.     

Multiple spatial scale factors affecting mirid bug abundance and damage level in organic rice paddies

Mirid bugs, major insect pests in rice production, have dramatically expanded their range in Japan, resulting in increased economic losses especially for organic rice farmers. In this study, the within-field and landscape-scale factors affecting the bug and its damage to crops were examined in organic rice farms. Bug densities and crop damage levels showed significant positive relationships with weed densities (Schoenoplectus juncoides and Echinochloa crus-galli) within individual fields. Bug densities were negatively associated with Tetragnatha spp. and Pachygnatha clercki densities, indicating that these spiders act as biological control agents that help to decrease crop damage levels. At the landscape scale, bug densities increased with the proportion of the area that was fallow within a 400-m radius around focal fields. Fallows represent important source habitat for the bug and the spatial extent at which bug abundance was affected indicates the mobility of these insects. These results suggest that the combination of biological control by natural enemies, and weed management within individual paddies and surrounding landscapes inside a buffer zone of less than half a kilometre may be effective in controlling mirid bugs and the damage they cause in organic paddy fields.     

Silverleaf nightshade,Solarium elaeagnifolium,origin, distribution,and relation to man

Silverleaf nightshade (Solanum elaeagnifolium) is a perennial weed that has become increasingly troublesome over the past several decades. Extensive use of soil-applied herbicides, accompanied by a reduction in annual weed competition and reduced tillage, have contributed to its spread and establishment as a serious pest. Crop plants are affected directly via competition and allelopathy or indirectly as the nightshade plants serve as hosts for destructive phytophagous insects or fungal pathogens. Probably native to the southwestern United States and northern Mexico,S. elaeagnifolium is now found in many semiarid regions of the world. Plants were used by the Pima, Kiowa and Navajo Indians in the preparation of food and in the tanning of leather. Containing the toxic glycoalkaloids solanine and solasonine, plants can cause livestock poisonings. The fruits, however, are a source of solasodine, which is used in the commercial manufacture of steroidal hormones.     

Life histories and host specificities of theEchium flea beetlesLongitarsus echii andL. Aeneus [Col. Chrysomelidae]

Two halticine flea beetles,Longitarsus echii Koch andLongitarsus aeneus Kutsch, occurring on the boraginaceous plantEchium plantagineum L. in the western Mediterranean region are potential biological control agents in Australia where the plant has become a weed (Paterson's curse). The adults of both species feed by making “shot holes” in the leaves. The larvae of both species attack the roots ofEchium, those ofL. echii feeding more centrally in the root than those ofL. aeneus which attack the outer cortex and rootlets. Both species are univoltine. The host restrictions of both flea beetles as adults and as larvae were tested using the criteria already established for theEchium leaf minerDialectica scalariella Zeller (Wapshere & Kirk, 1977). This testing established that it would be safe to introduce the 2 insects into Australia for the biological control ofE. plantagineum and they are now under quarantine.     

Insect herbivores associated with the introduced weed Bidens frondosa L. (Asteraceae) in Korea,and their potential role as augmentative biological control agents

The annual herb Bidens frondosa L., native to North America, is an invasive weed. Currently no information is available on the insect herbivores associated with this weed in Korea. A survey was carried out at two‐weekly intervals from May to October 2008 at two sites, and the incidence and abundance of various insect herbivores studied. A total nine species of insects was recorded and among them the defoliating caterpillar Hadjina chinensis (Wallengren) (Lepidoptera) was the only species known to have host plants restricted to genus Bidens. Further host specificity studies are required to evaluate the potential of this insect as a candidate for augmentative biological control agent for B. frondosa in Korea. All other insect species are either polyphagous or known crop pests.     

Invasive interactions: can Argentine ants indirectly increase the reproductive output of a weed?

The direct and indirect interactions of invasive ants with plants, insect herbivores, and Hemiptera are complex. While ant and Hemiptera interactions with native plants have been well studied, the effects of invasive ant–scale insect mutualisms on the reproductive output of invasive weeds have not. The study system consisted of Argentine ants (Linepithema humile), boneseed (Chrysanthemoides monilifera monilifera), and sap-sucking scale insects (Hemiptera: Saissetia oleae and Parasaissetia nigra), all of which are invasive in New Zealand. We examined the direct and indirect effects of Argentine ants on scale insects and other invertebrates (especially herbivores) and on plant reproductive output. Argentine ants spent one-third of their time specifically associated with scale insects in tending behaviours. The invertebrate community was significantly different between uninfested and infested plants, with fewer predators and herbivores on ant-infested plants. Herbivore damage was significantly reduced on plants with Argentine ants, but sooty mould colonisation was greater where ants were present. Herbivore damage increased when ants were excluded from plants. Boneseed plants infested with Argentine ants produced significantly more fruits than plants without ants. The increase in reproductive output in the presence of ants may be due to increased pollination as the result of pollinators being forced to relocate frequently to avoid attack by ants, resulting in an increase in pollen transfer and higher fruit/seed set. The consequences of Argentine ant invasion can be varied; not only does their invasion have consequences for maintaining biodiversity, ant invasion may also affect weed and pest management strategies.     

Testing biological control agent compatibility: Cyphocleonus achates and Larinus minutus on diffuse knapweed

While weed biological control success is typically achieved with one agent, multiple agents are invariably introduced. Biological control agents that share a host–plant may interact either directly or indirectly through changes in host–plant quality. Negative interactions could reduce the impacts of the agents on the density of their host–plant while positive interactions (facilitation) could improve biological control success.In the Okanagan Valley of British Columbia, Canada, initial declines in the invasive rangeland weed, diffuse knapweed (Centaurea diffusa) were attributed to the introduction of the weevil Larinus minutus. A second weevil, Cyphocleonus achates has recently become common on diffuse knapweed. We sought to determine if the recent increase of C. achates could threaten the success of L. minutus. We considered whether L. minutus colonisation or performance remained the same when C. achates was present, and whether the two agents acted independently to reduce plant performance.Neither changes in colonisation rates nor competitive interactions were apparent between C. achates and L. minutus. Both insects reduced plant performance and, for all metrics, the reduction in plant performance by one species was independent of the second. The two agents appear to be compatible and both should contribute to the control of diffuse knapweed. To assess how biological control agents interact requires understanding both their competitive interactions and their joint effects on the shared host.     

Stage specific feeding attributes and mobilization of nutrients in Mexican beetle,Zygogramma bicolorata Pallister on Parthenium hysterophorus L.

Parthenium hysterophorus L. (Asteraceae) is a toxic weed of agricultural farms, pastures and wastelands with a pan-tropical distribution. The weed causes a reduction in crop production of agricultural fields and severe health problems in humans. The Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) is among the most promising candidates for the weed biocontrol. However, no previous study has evaluated assimilation of nutrients in this beetle. In the present study, feeding attributes and assimilation of nutrients by larvae of Z. bicolorata were assessed on the weed. Results revealed that the first larval instars of Z. bicolorata exhibited lowest consumption rates, and accumulated minimum concentrations of glucose, proteins and triglycerides in their body. They showed compensatory feeding, and displayed highest food utilization efficiencies and developmental rates. In contrast, the fourth larval instars exhibited higher food consumption rates and conversion efficiencies, but displayed lowest developmental rates. Accumulation of food reserves was also recorded maximum for the fourth larval instars. Overall, the findings may aid current mass-rearing efforts for Z. bicolorata in laboratories, but field trials are still needed to strengthen the present findings.     

Cereal weeds variation in middle Egypt: Role of crop family in weed composition

Cereals occupies a major part in the diet of humans globally, participating more to our daily protein and calorie intake than any other crop. The present study highlight the weed flora of cereal crops compared to other crops in middle Egypt and their distribution. Ninety-two weed species were recorded in the all studied crops, cereal and other crops; in the studied area belong to 67 genera and 20 families. Egyptian clover; showed the highest numbers of both weed species and genera followed by wheat, on contrast the lowest weed species and genera numbers were recorded associated with Solanaceous crops tomato and pepper. Wheat crops exhibited the highest number of weed species, among cereals, followed by maize crop, while the lowest weed species number was detected in barley crop. Chenopodium murale, Cynodon dactylon, Convolvulus arvensis and Malva parviflora were the most frequent species in winter cereals, while Echinochloa colona, P. oleraceae were the most frequent weeds in summer cereals. Chorological analysis of the recorded weed species showed that cosmopolitan elements showed the highest numbers in total weed flora Differences in weed species compositions were fundamentally influenced by seasonal priority. Based on TWINSPAN and Ward classifications, crop family showed slightly effect as a factor affecting weed composition.     

The system management approach of biological weed control: Some theoretical considerations and aspects of application

Theoretical considerations behind the system management approach of biological weed control are presented. These include, a part describing and explaining the effects of parasitic fungi on crop – weed competition, a part describing and explaining the epidemic spread of parasitic fungi on weeds, and a part relating crop – weed competition at the population level to epidemics. The theoretical framework developed may also provide a basis for the use of other natural enemies, like insects, for biological weed control following the system management approach. Aspects of application are discussed using data of the interaction between the annual weed Senecio vulgaris and the rust fungusPuccinia lagenophorae.     

Host Status of Five Weed Species and Their Effects on Pratylenchus zeae Infestation of Maize

The host suitability of five of the most common weed species occurring in maize (Zea mays L.) fields in South Africa to Pratylenchus zeae was tested. Based on the number of nematodes per root unit, mealie crotalaria (Crotalaria sphaerocarpa) was a good host; goose grass (Eleusine indica), common pigweed (Amaranthus hybridus), and thorn apple (Datura stramonium) were moderate hosts; and khaki weed (Tagetes minuta) was a poor host. Only the root residues of khaki weed suppressed the P. zeae infestation of subsequently grown maize. When goose grass, khaki weed, and mealie crotalaria were grown in association with maize in soil infested with P. zeae, goose grass and khaki weed severely suppressed maize root development; this resulted in a low number of nematodes per maize root system and a high number of nematodes per maize root unit. Mealie crotalaria did not restrict maize root growth and did not affect nematode densities per maize root system or maize root unit. Special attention should be given to the control of mealie crotalaria, which is a good host for P. zeae, and goose grass, which, in addition to its ability to compete with maize, is also a suitable host for P. zeae.     

Epiblema tetragonana and Epinotia ustulana (Lepidoptera: Tortricidae), two potential biological control agents for the invasive plant,Rubus ellipticus

Himalayan yellow raspberry, Rubus ellipticus is one of the world’s 100 worst invasive alien species. The plant has become a serious problematic weed in Hawaii, USA and is naturalized in many other countries. Screening of potential biological control agents is being conducted in its native region in Asia. In this paper, we report on the field distribution, abundance and host specificity of two leaf-rolling moth species, Epinotia ustulana and Epiblema tetragonana (Lepidoptera: Tortricidae). In larval non-choice tests both species only developed on plants in the genus Rubus. However, in adult choice oviposition tests, both leaf rollers showed a strong preference for R. ellipticus over other species. Furthermore, leaf-rolls by these two insects were only found on R. ellipticus in the field. These results indicate the moths have a narrow host range. Our field surveys also showed that both moth species are widely distributed in Yunnan Province, southeastern China, with up to 115 leaf rolls per plant, suggesting high levels of damage. These findings indicate that the two insects have considerable potential for biological control of R. ellipticus, though further host range tests should be conducted using more native plant species in Hawaii.     

Host Status of Seven Weed Species and Their Effects on Ditylenchus destructor Infestation of Peanut

The host suitability to Ditylenchus destructor of seven common weed species in peanut (Arachis hypogaea) fields in South Africa was determined. Based on the number of nematodes per root unit, white goosefoot (Chenopodium album), feathertop chloris (Chloris virgata), purple nutsedge (Cyperus rotundus), jimson weed (Datura stramonium), goose grass (Eleusine indica), khaki weed (Tagetes minuta), and cocklebur (Xanthium strumarium) were poor hosts. Ditylenchus destructor survived on all weed species; population densities increased in peanut hulls and caused severe damage to seeds of peanut grown after weeds. Roots of purple nutsedge left in the soil suppressed populations of D. destructor and root and pod development in peanut grown after the weed. However, nematode populations in peanut hulls and seeds were not suppressed. Some weed species, especially purple nutsedge which is common in peanut fields, can be used to indicate the presence of D. destructor in the absence of peanut.     

Agropyrenol and agropyrenal,phytotoxins from Ascochyta agropyrina var. nana,a fungal pathogen of Elitrigia repens

A strain of Ascochyta agropyrina var. nana, a fungal pathogen of the perennial weed Elytrigia repens, produced several toxins in a liquid medium, and its primary toxin, named agropyrenol, was characterized as a substituted salicylaldehyde on the basis of its chemical and spectroscopic properties. Its absolute stereochemistry was determined by Mosher’s method. Two other minor metabolites were isolated from the same culture and named agropyrenal and agropyrenone, respectively. They were characterized as a trisubstituted naphthalene carbaldehyde and a pentasubstituted 3H-benzofuranone, respectively, using the same techniques. When assayed on leaves of several weed plants, i.e., Mercurialis annua, Chenopodium album and Setaria viridis, agropyrenol proved to be phytotoxic, causing the appearance of necrotic lesions, agropyrenal was less active, while agropyrenone was inactive. None of the compounds showed antibiotic, fungicidal or zootoxic activity.