Showing papers in "Biocontrol Science and Technology in 1994"
TL;DR: This review summarizes the progress and achievements made in the last decade in mass production formulation and application technology of the entomopathogenic fungus Beauveria bassiana and provides technological details about mass production of B. bassiana in China.
Abstract: This review summarizes the progress and achievements made in the last decade in mass production formulation and application technology of the entomopathogenic fungus Beauveria bassiana. Reports published on relevant research from Belgium, Canada, China, Cuba, Czechoslovakia (former), France, Germany, Great Britain, Philippines, Poland, Switzerland, USA and USSR (former) regarding this topic have been covered. Much of the non‐English language literature, particularly that from Eastern European and Chinese sources, has not been translated and is inaccessible to most English or other western language readers. We have done this translation and through this review provide technological details about mass production of B. bassiana in China. Various aspects of B. bassiana growth, substrate use, production of mycelia, conidiospore and blastospores, process technologies associated with separation, drying and milling, formulation, storage and ‘shelf‐life’, and field efficacy are reviewed. Data are presented on: a m...
512 citations
TL;DR: Simulation models suggest that wider at least some circumstances, transgenic plants bearing only one Bt gene may be more effective than sprays for delaying resistance to Bt.
Abstract: Insecticidal toxins from Bacillus thuringiensis (Bt) can now be deployed either in sprays or transgenic plants. Some entomologists and environmentalists have argued that the sprays are preferable to plants because they are less likely to cause resistance. However Bt sprays are not generally competitive with chemical insecticides and seem unlikely to displace them. In contrast, transgenic plants appear to be sufficiently effective to displace chemicals, making such plants attractive from the standpoint of environmental protection. Further, simulation models using data from the diamondback moth and a laboratory experiment using the Indianmeal moth suggest that wider at least some circumstances, transgenic plants bearing only one Bt gene may be more effective than sprays for delaying resistance to Bt Resistance in a laboratory‐selected strain of the Colorado potato beetle is especially interesting because a strain that can survive Bt sprays and develop to maturity cannot develop successfully on transgenic pl...
182 citations
TL;DR: The first field trials in Australia of transformed cottons expressing the CryIA(b) insecticidal protein from Bacillus thuringiensis subsp.
Abstract: The first field trials in Australia of transformed cottons expressing the CryIA(b) insecticidal protein from Bacillus thuringiensis subsp. kurstaki (Bt) were completed during the 1992–93 season. The trials showed good efficacy of the plants against field populations of Helicoverpa, but there were indications of a declining level of Bt expression once plants began to senesce. Laboratory assays showed that larger instars could survive on the transgenic tissues although their growth was severely retarded. The introduction of Bt transgenic cottons may have several ecological impacts, apart from their direct impact on target pests. These include the risk of resistance development, effects on beneficial and non‐target arthropod species and changes in pest status associated with altered patterns of pesticide usage. Chief among the potential pests are sucking insects (e.g. Miridae) which appear not to be regulated by beneficial agents and are currently suppressed by sprays applied for Helicoverpa Transgenic Bt pl...
155 citations
TL;DR: Whether the biology of insect pests of a number of cropping systems that are targets for toxin‐expressing plants fit assumptions that are conducive to slowing pest adaptation is discussed.
Abstract: We lack an empirical basis on which to judge the expected durability of crops that express one or more insecticidal proteins and must therefore rely upon theoretical population genetic models in assessing how best to delay pest adaptation to these toxins. A number of studies using such models indicate that expression of toxins at very high levels could slow pest adaptation to a crawl if the ecology and genetics of the pest and cropping system fit specific assumptions. These assumptions relate to: (1) inheritance of resistance factors; (2) ecological costs of resistance factors; (3) behavioral response of larvae and adults to the toxins; (4) plant‐to‐plant movement of larvae; (5) adult dispersal and mating behavior; and (6) distribution of host plants that do and do not produce the toxin(s). This paper includes a discussion of whether the biology of insect pests of a number of cropping systems that are targets for toxin‐expressing plants fit assumptions that are conducive to slowing pest adaptation. Emphas...
141 citations
TL;DR: Both V208 and V245 were pathogenic for P. chrysocephala and M. anisopliae, and their specificity for three other crucifer pests, Phaedon cochleariae, Myzus persicae and Lipaphis erysimi and a beneficial insect, Apis mellifera.
Abstract: The susceptibility of the cabbage stem flea beetle (Psylliodes chrysocephala; Coleoptera: Chrysomelidae) to different isolates of the entomogenous, hyphomycete fungi Beauveria bassiana and Metarhizium anisopliae, all from heterologous hosts, was investigated. The most pathogenic isolates were of M. anisopliae (V208, V233, V234, V242, V245, and V248). Studies were conducted to determine the virulence of V208 and V245, and their specificity for three other crucifer pests, Phaedon cochleariae, Myzus persicae and Lipaphis erysimi and a beneficial insect, Apis mellifera. Flea beetle mortality rates increased with dose; the estimated LC50 S of V208 and V245 at 14 days post‐inoculation were c. 106 conidia ml‐1. The respective estimated LT50 values of V208 and V245 for P. chrysocephala at 1 × 107 conidia ml‐1 were 10.0 and 9.3 days, and at 1 × 1010 conidia ml LT50s were 3.8 and 4.2 days. Both V208 and V245 were pathogenic for P. cochleariaeM. persicae and L. erysimi. Myzus persicae and L. erysimi died within 4 da...
124 citations
TL;DR: Strains showed a diversity in their ability to colonize roots: patterns of root colonization were similar, but the intensity and the speed of colonization differed according to the plant—fungus combination used.
Abstract: To characterize the ability of different strains of Fusarium oxysporum to colonize roots, and to analyze competition for root colonization between pathogenic and non‐pathogenic strains of F. oxysporum, it was necessary to develop specific labelling techniques for quantification of root colonization. Two methods were selected: the production of polyclonal antibodies, and the use of GUS‐transformed strains of F. oxysporum. The polyclonal antibodies recognized infected plants, and gave a minimum reaction with healthy plants, but were not specific for individual strains of F. oxysporum. These antibodies enabled total density of F. oxysporum to be assessed on roots, by ELISA. Metabolic activity of the root population of GUS‐marked strains was assessed by measuring the glucuronidase activity. Strains showed a diversity in their ability to colonize roots: patterns of root colonization were similar, but the intensity and the speed of colonization differed according to the plant—fungus combination used. Results de...
89 citations
TL;DR: Treatment with Pseudomonas putida WCS358r, a rifampicin‐resistant derivative of strain WCS358, significantly reduced fusarium wilt of carnation grown in rockwool if disease incidence was moderate, but not if Disease incidence was high.
Abstract: Treatment with Pseudomonas putida WCS358r, a rifampicin‐resistant derivative of strain WCS358, significantly reduced fusarium wilt of carnation grown in rockwool if disease incidence was moderate, but not if disease incidence was high. Differences in disease incidence could intentionally be established by varying the inoculum density of the pathogen Fusarium oxysporum f. sp. dianthi (Fod). The effectiveness of disease suppression by WCS358r increased with decrease of inoculum density and consequently decrease of disease incidence. WCS358r and a Tn5 marked derivative of WCS358 (B243) reduced fusarium wilt of carnation most effectively if a low iron availability for the pathogen was established by adding unferrated or only partially ferrated ethylenediamine [di(o‐hydroxyphenylacetic) acid]. A Tn5 mutant of WCS358 defective in siderophore biosynthesis (JM218) did not reduce disease incidence. Siderophore production and inhibition of Fod by WCS358r in vitro decreased with increasing iron availability, support...
76 citations
TL;DR: Several lines of evidence for a complex genetic basis for resistance in tobacco budworm Heliothis virescens and diamondback moth Plutella xylostella are reviewed, suggesting that a genetic approach based on linkage mapping, capable of simultaneously analyzing multiple physiological mechanisms, will be very useful in dissecting the complex trait of resistance.
Abstract: Recent studies have shown that the genetic basis of resistance to Bacillus thuringiensis (Bt) toxin in insects is far from simple. In this respect, it is similar to resistance to chemical insecticides, which is conferred by multiple physiological mechanisms under independent genetic control. Several lines of evidence for a complex genetic basis for resistance in tobacco budworm Heliothis virescens and diamondback moth Plutella xylostella are reviewed. This suggests that a genetic approach based on linkage mapping, capable of simultaneously analyzing multiple physiological mechanisms, will be very useful in dissecting the complex trait of resistance. In Heliothis, the existence of separate, independently assorting resistance genes has already been confirmed by linkage analysis with marker loci. This approach assists in the measurement of the relative potency of different resistance genes present in the same strain. Additionally, it facilitates comparative studies of the independent acquisition of homologou...
68 citations
TL;DR: Bioassays of transgenic rice plants, using R2 generation plants with two major rice insect pests, indicated that the transgenic plants are more resistant to the pests than are untransformed plants.
Abstract: Insect pests cause severe damage to rice production in many regions of the world. As a first step towards development of insect‐resistant rice, we introduced into japonica rice a truncated δ‐endotoxin gene cryIA(b) of Bacillus thuringiensis (Bt,), which has specific biological activity against lepidopteran insects. For high expression of the cryIA(b) gene in rice, the coding sequence was extensively modified, based on the codon usage of rice genes. Transgenic rice plants efficiently expressed the modified cryIA(b) gene at the levels of mRNA and protein. Bioassays of transgenic rice plants, using R2 generation plants with two major rice insect pests, striped stemborer (Chilo suppressalis) and leaf folder (Cnaphalocrosis medinalis), indicated that the transgenic plants are more resistant to the pests than are untransformed plants. Our results suggest that Bt toxin genes are useful for the development of new rice varieties resistant to major insect pests by genetic engineering.
58 citations
TL;DR: Resistance was delayed most when pure stands of transgenic plants were used with no refugia and the reproductive capacity of the insect was low, though this result may be dependent on the small population size examined.
Abstract: The effectiveness of two resistance management strategies (RMS) for transgenic crops was examined via simulation in single‐tactic (all fields in a population use the same strategy) and multi‐tactic (fields either employ transgenic plants or are treated by foliar Bacillus thuringiensis (Bt) applications) environments. The life tables and response to selection used in the simulations resembled those of a simplified, heliothine‐like species. In single‐tactic environments, the refuge strategy was the most effective approach for delaying the evolution of resistance to toxin genes incorporated into plants. Resistance was delayed most when pure stands of transgenic plants were used with no refugia and the reproductive capacity of the insect was low because the entire population became extinct, though this result may be dependent on the small population size examined (nine fields). With higher levels of reproduction, however, this strategy resulted in rapid evolution of resistance. When the insect populations wer...
56 citations
TL;DR: The antifungal properties of extracellular compounds produced by the epiphytic fungus Sporothrix flocculosa were bioassayed against phytopathogenie fungi on the basis of inhibition of spore germination, and mycelial growth and induction of cellular leakage.
Abstract: The antifungal properties of extracellular compounds produced by the epiphytic fungus Sporothrix flocculosa were bioassayed against phytopathogenie fungi on the basis of inhibition of spore germination, and mycelial growth and induction of cellular leakage. Following incubation in stationary culture, S. flocculosa released antifungal metabolites into the culture medium which were extractable with methylene chloride. When separated by thin layer chromatography, extracted metabolites yielded a compound(s) at Rf0.65 which inhibited development of Cladosporium cucumerinum and several other phytopathogenic fungi. Treatment of Botrytis cinerea and Fusarium oxysporum f.sp. radicis‐lycopersici (FORL) with the same compound(s) greatly reduced spore germination and biomass growth of both fungi. Additionally, both B. cinerea and FORL leaked electrolytes and proteins when grown in presence of the metabolites. Observations under electron microscopy revealed that FORL reacted to the presence of S. flocculosa metabolite...
TL;DR: Competition experiments with brush border membrane vesicles of diamondback moth larvae suggested a model with a single binding site for CryIA(b), and heterologous competition showed thatCryIA(c) competed as effectively as CryIA(-b) for the CryIA (b) binding site, whereas CryIA('a) competed less effectively.
Abstract: Competition experiments were performed with brush border membrane vesicles of diamondback moth larvae using 125I‐labelled CryIA(b) and unlabelled CryIA(a), CryIA(b) and CryIA(c). The results suggested a model with a single binding site for CryIA(b). Heterologous competition showed that CryIA(c) competed as effectively as CryIA(b) for the CryIA(b) binding site, whereas CryIA(a) competed less effectively. Toxicity tests were performed on third instar larvae with trypsin‐activated insecticidal crystal proteins (ICPs) and a commercial formulation of Bacillus thuringiensis (Bt) (Dipel). A laboratory colony was found to be susceptible to all four ICPs tested and to Dipel. CryIA(b), CryIA(c) and CryIB were approximately equally toxic, and CryIA(a) was less toxic than the other ICPs by one order of magnitude. In contrast, a recently collected insect population from the Philippines was 236 times less susceptible to CryIA(b) than the control colony. However, for the other ICPs no significant differences were found ...
TL;DR: The aim of this paper is to put the traditional approaches to plant breeding for cultivar development and seed marketing options for commercial release of transgenic crops into perspective.
Abstract: Genetic engineering offers considerable potential for the development of insect‐resistant crop plants through the transfer and expression of Bacillus thuringiensis genes encoding insecticidal proteins A potential problem with the use of such crops is the possibility of insects adapting to overcome the resistance mechanism Strategies to minimize this risk have included concepts of seed mixtures and crop rotations This may involve genotypes transformed with a series of genes encoding different resistance mechanisms and/or manipulating the manner in which these genes are expressed The aim of this paper is to put these strategies into perspective with respect to the limitations imposed by the nature of plant transformation, the traditional approaches to plant breeding for cultivar development and seed marketing options for commercial release of transgenic crops The optimum strategy for any specific crop varies depending on whether the cultivar targeted for release is a clone, an inbred line, a hybrid or
TL;DR: A significant additive effect on attractiveness for two odours in traps provided with both the visual and the olfactory cues as compared to traps with either cue alone is found, but these results could not easily be reproduced in greenhouses.
Abstract: Sticky blue traps are a suitable and important tool for Western Flower Thrips population monitoring in greenhouses. They can be used in vegetables and in ornamentals, and provide important information on the current status of the pest population. However, such traps cannot be used in some susceptible plant species when they are flowering because at that stage the plants are more attractive to Western Flower Thrips than the traps. We therefore tried to increase trap attractiveness by combining the colour cue with an attractive odour cue. In laboratory experiments, we found a significant additive effect on attractiveness for two odours in traps provided with both the visual and the olfactory cues as compared to traps with either cue alone. However, these results could not easily be reproduced in greenhouses. The main factors responsible for this failure seem to be (1) the only moderate, additive increase of trap attractiveness when using combined visual and olfactory cues, and (2) the problems associated wi...
TL;DR: A method of selecting a Steinernema feltiae strain that is effective against a mushroom fly, Lycoriella solani, is described in detail and a 4‐fold improvement in nematode ability to find and parasitize third‐ and fourth‐instar larvae of the pest in the mushroom substrate is achieved.
Abstract: A method of selecting a Steinernema feltiae strain that is effective against a mushroom fly, Lycoriella solani, is described in detail. The pest control efficacy of the selected nematode strain was evaluated and compared with the efficacy of two unselected strains. The selection procedure was designed to give preference to nematode individuals with the greatest ability (1) to search effectively for the target insect larvae in their natural habitat, (2) to infect them shortly after application and (3) to reproduce in their haemocoel. Thirty‐four rounds of selection achieved a 4‐fold improvement in nematode ability to find and parasitize third‐ and fourth‐instar larvae of the pest in the mushroom substrate. In 24‐h laboratory experiments, mortality of the insect caused by nematode juveniles rose from 22.5%, recorded for the original unselected isolate, to 92.5% for the selected strain. In a 51‐day experiment conducted on a mixed age mushroom house population of L. solani, the enhanced pest control ability o...
TL;DR: It was demonstrated that the mycopesticide currently under development for the control of locusts and grasshoppers was quantifiably less hazardous to bees than the chemical pesticide.
Abstract: A technique was developed to allow ultra‐low volume (ULV) application of an oil formulation of the deuteromycete, Metarhizium flavoviride Gams & Rozsypal, to Apis mellifera (Linnaeus). In the first experiment, application of a dose equivalent to twice the expected field application rate killed 30% of the bees and a twenty‐fold dose killed 87%. In a second experiment, a realistic field dose formulated in oil killed 11% of the bees and a similar dose formulated in water killed 8%. The dose applied effectively killed the target host, the desert locust Schistocerca gregaria (Forskal). Application of a chemical pesticide comprising an organophosphate and two pyrethroids at a dose that was just sub‐lethal to locusts, killed all treated bees. Very few untreated bees died. The results demonstrated the feasibility of safety testing a mycopesticide with bees as a non‐target organism. In addition, it was demonstrated that the mycopesticide currently under development for the control of locusts and grasshoppers was quantifiably less hazardous to bees than the chemical pesticide
TL;DR: The laboratory test assesses pesticide effects on the ‘most exposed’ life stage of the parasitic wasp Opius concolor, and it has been developed and interpreted according to the guidelines of the IOBC/WPRS Working Group ‘Pesticides and Beneficial Organisms ‘.
Abstract: The laboratory test described in the present paper assesses pesticide effects on the ‘most exposed’ life stage of the parasitic wasp Opius concolor, and it has been developed and interpreted according to the guidelines of the IOBC/WPRS Working Group ‘Pesticides and Beneficial Organisms ‘. The evaluation of results is based on longevity and parasitism of adult females exposed to afresh residue of pesticide on a glass surface. Longevity measurements were based on the time of exposure required to cause 50% mortality (LT50) and were compared to a standard control LT50 in order to calculate the reduction caused by the pesticide. Parasitism was surveyed by means of three sequential determinations: the number of days that females were seen parasitizing, the mean number of attacked hosts and the progeny size per female. These determinations were also compared to a control to calculate the impact of pesticides. Using this ‘worst case’ situation, pesticides reducing the beneficial capacity of O. concolor below the ...
TL;DR: Two specific endophagous parasitoids Gyranusoidea tebygi and Anagyrus mangicola, of Indian origin, were mass‐reared at the International Institute of Tropical Agriculture in Cotonou and released against the mango mealybug Rastrococcus invadens, in collaboration with national biological control programmes.
Abstract: Two specific endophagous parasitoids Gyranusoidea tebygi and Anagyrus mangicola, of Indian origin, were mass‐reared at the International Institute of Tropical Agriculture in Cotonou and released against the mango mealybug Rastrococcus invadens, in collaboration with national biological control programmes. G. tebygi was released in the following countries: Benin, Gabon, Ghana, Nigeria, Sierra Leone and Zaire. In Togo, it had been released earlier and studied during another project. This parasitoid is now established in all areas infested by the mango mealybug. In addition, it established itself without previous release in Congo and Cote d'Ivoire. A. mangicola has been released in Benin, Gabon and Sierra Leone since 1991, and by mid‐1993 was recovered from a few sites. It seems locally established in southern Benin.
TL;DR: A predictive phenological model is described for the parasitoid Microctonus hyperodae, introduced to New Zealand as a potential biological control agent against Argentine stem weevil Listronotus bonariensis, allowing early predictions of its phenology in different parts of the target pest's New Zealand range.
Abstract: A predictive phenological model is described for the parasitoid Microctonus hyperodae, introduced to New Zealand as a potential biological control agent against Argentine stem weevil Listronotus bonariensis. The model is based on development/temperature relationships obtained from experiments on the parasitoid in quarantine prior to its release, allowing early predictions of its phenology in different parts of the target pest's New Zealand range. In particular the model was used to predict the number of parasitoid generations each year, the degree of temporal synchrony between parasitoid adults and the susceptible adult pest stage, the order of parasitism and reproduction in the pest's life cycle as a possible basis for a simplified, discrete host/parasitoid population model, and the likely significance of ecotypic differences in development and diapause characteristics of the parasitoid. These applications demonstrate the potential for simple models to help in climate matching of classical biological con...
TL;DR: It is argued that the analysis is best done with the predation rate as response and a test for the location of its maximum is defined.
Abstract: The aim of this paper is to highlight the benefits of a full data analysis of a functional response data set, compared to the usual one‐pass regression analysis In a biological control setting where the choice of organism is often based on comparative studies of the functional responses, it is imperative to have both reliable estimates and a feeling of the degree of confidence one is willing to put on the figures We analyzed a data set involving the freshwater predator Notonecta glauca (Hemiptera) preying on Asellus aquaticus during 24 h The specific aim of the analysis was to test whether the functional response is of type II or type III The different stages of a complete analysis are (1) a preliminary inspection of the data, (2) model building, (3) a model check and (4) a combination of the results with independent information We argue that the analysis is best done with the predation rate as response and define a test for the location of its maximum The existence of a maximum is typical for type
TL;DR: The nematodes Phasmarhabditis hermaphrodita, a parasite of slugs, was cultured in vitro and applied as a drench in two outdoor mini‐plot field experiments to test the capacity of the nematode to protect Chinese cabbage seedlings and wheat seeds from damage by the field slug Deroceras reticulatum.
Abstract: The nematode Phasmarhabditis hermaphrodita, a parasite of slugs, was cultured in vitro and applied as a drench in two outdoor mini‐plot field experiments to test the capacity of the nematode to protect Chinese cabbage seedlings and wheat seeds from damage by the field slug Deroceras reticulatum. The first experiment compared a single dose of nematodes (2 X 1010 ha‐1) with methiocarb pellets added at the recommended field rate (5.5 kg.product ha‐1 ) and untreated plots. Plots treated with either nematodes or methiocarb pellets had significantly less slug damage than untreated plots and, from the third week onwards, there was significantly less slug damage on plots treated with nematodes than on methiocarb‐treated plots. At the end of the experiment, 6 weeks after treatment, both slug numbers and biomass were significantly higher in untreated plots than in either methiocarb‐treated or nematode‐treated plots. In the second experiment, six nematode doses ranging from 1 X 10 8 to 2 X 1010 ha‐1 were compared wi...
TL;DR: In seven strains of Plutella xylostella, the first insect with field populations reported to be resistant to Bt, resistance declined when exposure to insecticide ceased, and reduced biotic fitness associated with resistance is the most likely cause of instability of resistance.
Abstract: The continued efficacy of environmentally safe biopesticides derived from Bacillus thuringiensis (Bt) is threatened by the potential for development of resistance in pest populations. Instability of resistance is defined here as the tendency for the frequency of resistant genotypes to decrease in a population beyond effects directly attributable to immigration or emigration. Instability can be quantified as R, the average rate of change in the logarithm of the LC50 (concentration killing 50% of individuals) per generation, which is analogous to the average rate of response to selection per generation. In seven strains of Plutella xylostella, the first insect with field populations reported to be resistant to Bt, resistance declined when exposure to insecticide ceased (mean R = − 0.19). In four other pests, resistance to Bt declined slowly or not at all (mean R = − 0.02) in the absence of exposure to Bt Reduced biotic fitness associated with resistance is the most likely cause of instability of resistance ...
TL;DR: The mortality of second instar larvae up to 41 days in treatments with both pathogens together was significantly greater than the additive mortalities of single pathogen treatments, and therefore synergistic, and the use of a dual pathogen system for control of grass grub larvae is discussed.
Abstract: Larvae of the New Zealand grass grub (Costelytra zealandica) were treated with the entomopathogenic fungus, Metarhizium anisopliae, and the bacterium, Serratia entomophila, singly and in combination. The mortality of second instar larvae up to 41 days in treatments with both pathogens together was significantly greater than the additive mortalities of single pathogen treatments, and therefore synergistic. Treatment of third instar larvae with both pathogens did not increase mortality compared with the fungus alone. Second instar larvae were more resistant to M. anisopliae than third instar larvae. S. entomophila causes a chronic disease and bacterial treatments alone resulted in disease, but little mortality for either instar within 5 weeks. In both fungus alone and fungus/bacteria treatments, less than half the cadavers supported fungal sporulation. The use of a dual pathogen system for control of grass grub larvae is discussed.
TL;DR: The two most effective strains seem to be well adapted to low temperature, which is likely to be the most important limiting factor for nematode activity in the mountain spruce forests.
Abstract: Field tests were conducted in the Asiago Forest, Venetian Prealps (Italy) to evaluate the efficacy of nematode strains (Heterorhabditis sp. HL 81 Steinernema carpocapsae IS 230 S. feltiae C = bibionis,) IS 389 S. kraussei SK) against the spruce web‐spinning sawfly Cephalcia arvensis. Soil applications of 100 juveniles cm‐2 of S. feltiae and S. kraussei resulted in 56% and 36.4% reduction of emergences of sawfly, respectively, when performed before the mature larvae drop and enter the soil. The effectiveness of S. feltiae becomes 32.3% if the nematodes are applied when the larvae have already prepared their chambers. S. feltiae parasitized more females and long‐term diapausing individuals than S. kraussei. The two most effective strains (IS 389 and SK) seem to be well adapted to low temperature, which is likely to be the most important limiting factor for nematode activity in the mountain spruce forests. An ichneumonid parasitoid (Xenoschesis fulvipes,) was strongly affected by S. feltiae, resulting in 66....
TL;DR: The Colorado potato beetle is a severe pest of potatoes in the US, and has developed field resistance to almost every insecticide used against it, and is considered to be a model species for insecticide resistance.
Abstract: The Colorado potato beetle is a severe pest of potatoes in the US. It has developed field resistance to almost every insecticide used against it, and is considered to be a model species for insecticide resistance. We have recently reported the selection of a Bacillus thuringiensis (Bt) resistant strain of beetle (Bt‐R). We have tested this strain and susceptible beetles (Bt‐S) against transgenic potato plants in 96‐h (first instars through adults) and complete development bioassays (second instars through adults). The Bt‐R strain first instars were almost as susceptible to transgenic plants as the Bt‐S strain, but second instars were significantly different from controls in longevity and weight gained (P<0.01). Adult Bt‐R beetles averaged 25% mortality over 14 days, and each of the younger instars (fourth, third and second) experienced greater mortality. The operational and ecological implications of potential Bt resistance on deployment of transgenic potato plants are discussed.
TL;DR: A rapid procedure is developed, where transgenic white clover plants regenerate directly from the cotyledonary axil of germinated seedlings and can be transferred into the glasshouse within 42 days of culture initiation, which offers the opportunity to improve the sustainability ofwhite clover in New Zealand pastures by introducing pest resistance genes directly into these plants.
Abstract: The destructive effects of indigenous insects on pasture plants are a significant cause of diminished pastoral productivity in New Zealand. Identification of white clover genotypes with natural immunity against native insects has not been successful, so farmers use chemical sprays to control pest populations. An alternative strategy to reduce insect damage to white clover is through development of a transformation system using Agrobacterium‐mediated transfer DNA. We have developed a rapid procedure, where transgenic white clover plants regenerate directly from the cotyledonary axil of germinated seedlings and can be transferred into the glasshouse within 42 days of culture initiation. This technology offers the opportunity to improve the sustainability of white clover in New Zealand pastures by introducing pest resistance genes directly into these plants. Insect feeding bioassays have identified several serotypes of Bacillus thuringiensis (Bt) with δ‐endotoxins active against larvae of the lepidopteran pe...
TL;DR: The infection of grasshoppers by naturally occurring, entomopathogenic fungi was monitored at two sites in Malanville, northern Benin, Africa and M. flavoviride sporulated on most grasshopper cadavers within 10 days of collection.
Abstract: The infection of grasshoppers by naturally occurring, entomopathogenic fungi was monitored at two sites in Malanville, northern Benin, Africa. Grasshoppers were collected and recorded from the sites between June and December 1992 and all of them, barring the first instars, were incubated in ventilated cages. At the first site, 1343 individuals of 35 grasshopper species were incubated, and at the second site, 857 individuals of 36 grasshopper species were incubated. Three hyphomycete fungi (Deuteromycotina: Hyphomycetes), Metarhizium flavoviride Gams and Rozsypal, Beauveria bassiana (Bals.) Vuillemin and Sorosporella sp. were found infecting grasshoppers. The average incidence of M. flavoviride infection was 2.9% and 1.8% at the two sites for all host species. M. flavoviride sporulated on most grasshopper cadavers within 10 days of collection. B. bassiana and Sorosporella sp. were only collected from one and five grasshopper individuals respectively. A significant difference was noted in the time to death ...
TL;DR: The production of ALS 84 might play a role in the complex mechanism of biological control of crown gall, especially in strains resistant to agrocin 84 and sensitive to ALS 84, and by the creation of an ecological niche favourable to A. radiobacter strains K84, K1026 or K84 Agr‐.
Abstract: Agrobacterium radiobacter strains K84, K1026 and K84 Agr‐ produced in vitro an antibiotic‐like substance (ALS 84), different from agrocin 84 and observed in mannitol‐glutamate medium. Twenty five out of 39 A. tumefaciens strains of biovars 1, 2 and 3 were sensitive to ALS 84 regardless of their sensitivity to agrocin 84. Sensitivity in A. tumefaciens strain C58 was not encoded by the Ti‐plasmid. Most isolates tested of Erwinia carotovora subsp. carotovora E. carotovora subsp. atroseptica, Pseudomonas corrugata P. cichorii and unidentified isolates from galls were also sensitive to this substance. ALS 84 was not affected by the proteases studied, nor by treatment at 62°C for 30 min and had a bacteriostatic effect. The production of ALS 84 might play a role in the complex mechanism of biological control of crown gall, especially in strains resistant to agrocin 84 and sensitive to ALS 84, and by the creation of an ecological niche favourable to A. radiobacter strains K84, K1026 or K84 Agr‐.
TL;DR: Bioassays against the aphid Myzus persicae showed no detectable difference in virulence between the clone of V291 which contained dsRNA and the clone that did not, and both of which had been subcultured successively on solid medium.
Abstract: Nucleic acids from 41 strains of Metarhizium anisopliae, obtained from different parts of the world were extracted and examined by electrophoresis. Strong bands of double‐stranded RNA (dsRNA) were detected in two isolates from Brazil, V215 and V291, which had, respectively, 13 and 9 distinct bands ranging in size from ca. 0.75 to 3.5 kb. Icosahedral virus‐like particles (VLPs) (ca. 33 nm in diameter) were observed by transmission electron microscopy in extracts of these isolates. The VLPs and dsRNA were both absent from a clone of the isolate V291 which had been subcultured successively on solid medium. Bioassays against the aphid Myzus persicae showed no detectable difference in virulence between the clone of V291 which contained dsRNA and the clone that did not.
TL;DR: There was a positive relationship between the weight of 7–10‐day‐old host puparia and percentage of emergence for both D. longicaudata and P. fletcheri and standardization of shipping methods included placement of ice blocks in the top levels of the ice chests, prompt shipment and pick‐up of samples, and cooling of puparia before shipment to minimize metabolic heat generated in the samples.
Abstract: Criteria were established to improve quality control methods for augmentative releases of the opiine parasitoids, Diachasmimorpha longicaudata (Ashmead) and Psyttalia fletcheri (Silvestri). These included correlating puparial weight with adult emergence and sex ratio at the Honolulu rearing facility, and determining the effect of air shipments and field releases on parasitoid emergence and subsequent mortality. There was a positive relationship between the weight of 7–10‐day‐old host puparia and percentage of emergence for both D. longicaudata and P. fletcheri. Standardization of shipping methods included placement of ice blocks in the top levels of the ice chests, prompt shipment and pick‐up of samples, and cooling of puparia before shipment to minimize metabolic heat generated in the samples, and to delay emergence of samples. Before standardization, emergence losses of up to 58% were observed for D. longicaudata and 18% for P. fletcheri. When shipping methods were standardized, emergence was no longer ...