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At least 415 records · Page 23Linked to original sources
PubMed2002

Aphid prey suitability as environmental effect on Adalia bipunctata reproduction.

Secondary plant metabolites (allelochemicals) play a major role in plant-insect interactions. Glucosinolates (GLS) and their degradation products from Brassica species are attractants and feeding stimulants for Brassicaceae specialist insects but are generally repellent and toxic for generalist herbivores. The impact of these compounds on crucifer specialist insects are well known but their effect on generalist predators is still not well documented. Prey host plant influence on reproduction of an aphidophagous beneficial, the two spot ladybird, was determined using the cabbage aphid, Brevicoryne brassicae reared on a crucifer plant, namely Brassica napus containing low GLS levels. As ladybird developmental and reproductive parameters were already shown to be strongly affected by the allelochemical presence in its preys, the unsuitable aphid and host plant combination was only momentary used to feed the A. bipunctata adults. A strong impact of the diet was observed on the beetle fecundity and the emerging offspring. Changing B. brassicae aphid to a suitable prey slowly improved the temporary negative effect of the former diet. These results enhance the food environmental effect and the importance of tritrophic relations in pest management strategies by predators. Indeed, more than the choice of the beneficial species, the prey host plant has a major influence on the potential efficacy of biological agent to control herbivore species such as aphids.

Animals↗
PubMed2004

Occurrence of Puccinia isiacae on Phragmites australis in Saudi Arabia and its possibility as a biological control agent.

During the summer of 2002, symptoms of rust disease were observed for the first time on Phragmites australis in Saudi Arabia. Light brown lesions of regular shape indicating uredinia of Puccinia isiacae appeared on the leaves. The morphology and characteristics of the fungus were described in detail with both light and scanning electron microscopy. The possibility of using this fungus as a biological control agent was also discussed.

Basidiomycota↗
PubMed2004

Influence of agricultural practices on fusarium infection of cereals and subsequent contamination of grain by trichothecene mycotoxins.

Fusarium head blight (FHB) of small grain cereals and ear rot in maize are significant diseases across the world. Infection can not only result in reduced yield as a result of shrunken grains but also result in reduced milling and malting quality and the contamination of grains with mycotoxins. Mycotoxins are hazardous to animal and human health. Therefore, guidelines and legislation are in place, or under consideration, in most countries to protect consumers and animal welfare. As fusarium mycotoxins are produced within the growing crop, it is important to understand how agricultural practices affect mycotoxin contamination of grain. Such information could then be used to determine guidelines on "Good Agricultural Practice" (GAP) to minimise the mycotoxin contamination of cereal products. Evidence is provided to show the importance of choice of cultivar, crop rotation, soil cultivation, fertiliser and the chemical and biological control of insects, weeds and fungi.

Agriculture↗
PubMed1989

The potential role of pathogens in biological control.

It is now well established that pathogens such as viruses, fungi bacteria and protozoans can have profound effects on the dynamics of their invertebrate host populations. Theoretical models of invertebrate host-pathogen interactions which assume uniform structure of the pathogen population may reasonably explain the oscillatory behaviour observed in some systems, but do not adequately describe the existence of more constant populations found in other host-pathogen interactions. An examination of the literature relating to these relatively stable systems suggests that the common thread is the eventual transmission of some of the more protected, longer-lived stages of the pathogen occurring in reservoirs, such as the soil, host cadavers on trees, or the live host itself. In this letter, I propose a new theoretical model which incorporates this population structure and accounts for the range of dynamics observed in natural systems. In particular, I show that host populations may be regulated to low and relatively constant densities if sufficient numbers of pathogens are trans-located from pathogen reservoirs to habitats where transmission can occur. An understanding of pathogen reservoirs may be of value in the design of biological control programmes and may greatly increase the effectiveness of pathogens as biological control agents.

Animals↗
PubMed1995

Regulatory factors affecting larval mosquito populations in container and pool habitats: implications for biological control.

Empirical studies have shown that populations of larval mosquitoes developing in ground pools are subjected to different mortality factors than populations developing in water-filled containers. In general, larvae in ground pools are limited by natural enemies whereas those in containers are limited by resource availability. Containers also are typically smaller than ground pools and lack appreciable internal primary productivity. These physical and biological features have significant implications for successful implementation of biological control agents. Island biogeography theory suggests that container habitats will support smaller populations of fewer species compared to ground pools, implying that it may be more difficult to establish natural enemies in container habitats. The lack of primary productivity within containers may limit the number of trophic levels and reduce the likelihood of establishing and maintaining predator populations. Most importantly, larval mosquito populations in containers are regulated by competitive interactions, and mortality from natural enemies is likely to be compensatory. These habitat and population characteristics, combined with difficulties in locating and treating containers, suggest that successful control of ground pool mosquitoes using biological control agents is more feasible.

Animals↗
PubMed1993

Laboratory investigations on the larval zoophagy of Ophyra capensis--an antagonist of Musca domestica.

Second and third instar larvae of Ophyra capensis are distinct predators. Although facultative, their zoophagy is so strong that they show cannibalism in the absence of prey. If house fly larvae are available, the predators can kill up to 17 prey per larva of the predator depending on the larval instar and the culture density. The highest effectiveness under laboratory conditions was observed at densities from 1.7 to 3.0 g substrate per larva from the culture and at a ratio between predators and prey from 1:6 to 1:12. Under these conditions the reduction of house fly numbers as a result of O. capensis action is over 70%. If the natural elimination during house fly development (in our experiments from the second larval instar up to the adult eclosion it is not less than 10%) also is taken into account, it seems that under these conditions at the most 20% of M. domestica can develop to the adult stage. The similar requirements of biotopes and substrates for the preadult development of O. capensis and M. domestica, the high predator activity and the big food portion give a good reason to conclude that O. capensis is a perspective agent for biological house fly control.

Animals↗
PubMed2001

Mass production of entomopathogenic nematodes for plant protection.

Entomopathogenic nematodes of the genera Heterorhabditis and Steinernema are commercially used to control pest insects. They are symbiotically associated with bacteria of the genera Photorhabdus and Xenorhabdus, respectively, which are the major food source for the nematodes. The biology of the nematode-bacterium complex is described, a historical review of the development of in vitro cultivation techniques is given and the current use in agriculture is summarised. Cultures of the complex are pre-incubated with the symbiotic bacteria before the nematodes are inoculated. Whereas the inoculum preparation and preservation of bacterial stocks follow standard rules, nematodes need special treatment. Media development is mainly directed towards cost reduction, as the bacteria are able to metabolise a variety of protein sources to provide optimal conditions for nematode reproduction. The process technology is described, discussing the influence of bioreactor design and process parameters required to obtain high nematode yields. As two organisms are grown in one vessel and one of them is a multicellular organism, the population dynamics and symbiotic interactions need to be understood in order to improve process management. Major problems can originate from the delayed or slow development of the nematode inoculum and from phase variants of the symbiotic bacteria that have negative effects on nematode development and reproduction. Recent scientific progress has helped to understand the biological and technical parameters that influence the process, thus enabling transfer to an industrial scale. As a consequence, costs for nematode-based products could be significantly reduced.

Animals↗
PubMed1997

Dispersal and parasitizing abilities of Eupelmus vuilleti (Hymenoptera: Eupelmidae) within a column of cowpea seeds.

Eupelmus vuilleti (Crawford) is an ectoparasitoid of the seed-eating beetle Bruchidius atrolineatus (Pic), which is an important pest of stored cowpea, Vigna unguiculata Walp, seeds in West Africa. Herein, we investigated the dispersal abilities of females within columns of seeds to assess the potential of E. vuilleti as a biological control agent of bruchids in cowpea granaries. The influence of host presence together with the 2 abiotic factors light and gravity on parasitoid movement and parasitization efficiency were analyzed. E. vuilleti females were able to travel through large seed masses and parasitize hosts located at the end of the seed column opposed to their introduction zone. Parasitoid movement was stimulated by light. E. vuilleti females exhibited a negative geotropism. Females introduced at the bottom of the seed column dispersed more and parasitized more hosts than females introduced at the top. Host presence had some influence on the dispersal of the parasitoids within the seed column at a host density of 10 infested seeds for 16,000-18,000 uninfested seeds. This depended on female introduction zone because gravity was the major factor influencing dispersal. The possible applications of these results for biological control of bruchids in cowpea granaries are discussed.

Animals↗
PubMed2003

Rapid evolution and the cost of resistance to Bacillus thuringiensis in greenhouse populations of cabbage loopers, Trichoplusia ni.

The microbial insecticide Bacillus thuringiensis (Bt) has become the mainstay of non-chemical control of Lepidopteran pests, either as sprays or through the incorporation of Bt toxins into transgenic crops. Given the wide use of Bt, it is striking that currently only one pest species, Plutella xylostella, has been reported to have developed significant resistance to Bt outside the laboratory. By contrast, we report here the frequent and rapid development of resistance to B. thuringiensis kurstaki (Dipel, Abbott) in populations of cabbage loopers, Trichoplusia ni, in commercial greenhouses. Resistance to Bt appears to be costly and there is a rapid decline of resistance in populations collected from greenhouses and maintained in the laboratory without selection. Management of pests resistant to Bt in vegetable greenhouses will require sporadic use of Bt-based sprays or alternatively use of sprays containing other Bt toxins.

Animals↗
PubMed2000

Spider-mite problems and control in Taiwan.

Problems with spider mites first appeared in Taiwan in 1958, eight years after the importation of synthetic pesticides, and the mites evolved into major pests on many crops during the 1980s. Of the 74 spider mite species recorded from Taiwan 10 are major pests, with Tetranychus kanzawai most important, followed by T. urticae, Panonychus citri, T. cinnabarinus, T. truncatus and Oligonychus litchii. Most crops suffer from more than one species. Spider mites reproduce year-round in Taiwan. Diapause occurs only in high-elevation areas. Precipitation is the most important abiotic factor restricting spider-mite populations. Control is usually accomplished by applying chemicals. Fifty acaricides are currently registered for the control of spider mites. Acaricide resistance is a serious problem, with regional variation in resistance levels. Several phytoseiid mites and a chrysopid predator have been studied for control of spider mites with good effect. Efforts to market these predators should be intensified so that biological control can be a real choice for farmers.

Animals↗
PubMed2006

Development of synthetic food-related attractant for Carpophilus davidsoni and its effectiveness in the stone fruit orchards in southern Australia.

An effective synthetic attractant, based on host-related volatile compounds, was developed for the nitidulid beetle, Carpophilus davidsoni, as part of a program for managing this pest in Australian peach orchards. Fermenting peach juice and whole peaches and nectarines served as chemical models for the attractant, and synthetic formulations were sought that matched the natural sources, both with respect to emission rates of key chemicals (in ng/min) and attractiveness to flying beetles. All volatile sources were kept in airstreams during laboratory chemical measurements, and these airstreams were subsequently directed to the wind-tunnel behavioral assay, allowing the determined emission rates of compounds to be associated with particular levels of attractiveness. Chemical sampling of airstreams was by solid-phase microextraction, and analysis was by gas chromatography and mass spectrometry. A volatile delivery system was coupled to the wind tunnel and allowed facile manipulation of natural and synthetic scents. The final blend, modeled after fermenting peach juice, contained ethanol as the main constituent and 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, acetaldehyde, and ethyl acetate as minor constituents, all in water solution. Blend components were synergistic, and use of a mixture was essential for optimal attractiveness. The synthetic blend was highly effective in the field and is intended to replace fermenting peach juice and overripe peaches, which were previously used as synergists of the Carpophilus spp. aggregation pheromones in attract-and-kill stations.

Animals↗
PubMed2001

Monarch larvae sensitivity to Bacillus thuringiensis- purified proteins and pollen.

Laboratory tests were conducted to establish the relative toxicity of Bacillus thuringiensis (Bt) toxins and pollen from Bt corn to monarch larvae. Toxins tested included Cry1Ab, Cry1Ac, Cry9C, and Cry1F. Three methods were used: (i) purified toxins incorporated into artificial diet, (ii) pollen collected from Bt corn hybrids applied directly to milkweed leaf discs, and (iii) Bt pollen contaminated with corn tassel material applied directly to milkweed leaf discs. Bioassays of purified Bt toxins indicate that Cry9C and Cry1F proteins are relatively nontoxic to monarch first instars, whereas first instars are sensitive to Cry1Ab and Cry1Ac proteins. Older instars were 12 to 23 times less susceptible to Cry1Ab toxin compared with first instars. Pollen bioassays suggest that pollen contaminants, an artifact of pollen processing, can dramatically influence larval survival and weight gains and produce spurious results. The only transgenic corn pollen that consistently affected monarch larvae was from Cry1Ab event 176 hybrids, currently <2% corn planted and for which re-registration has not been applied. Results from the other types of Bt corn suggest that pollen from the Cry1Ab (events Bt11 and Mon810) and Cry1F, and experimental Cry9C hybrids, will have no acute effects on monarch butterfly larvae in field settings.

Animals↗
PubMed2006

Larvicidal diterpenes from Pterodon polygalaeflorus.

Ethanolic extract from seeds of Pterodon polygalaeflorus (Benth) has been shown to possess significant larvicidal activity against the mosquito Aedes aegypti. Bioassay-guided fractionation of the extract led to the isolation and characterization of the know diterpenoid furans 6alpha-hydroxyvouacapan-7beta,17beta-lactone (1), 6alpha,7beta-dihydroxyvouacapan- 17beta-oic acid (2) and methyl 6alpha,7beta-dihydroxyvouacapan-17beta-oate (3). The structures were established from infrared (IR), ultraviolet (UV), 1H-nuclear magnetic resonance (NMR), 13C-NMR, and mass spectral data: full NMR assignments are presented for compounds 1-3 and the diacetyl derivative of 3. Compounds 1-3 exhibited LC50 values of 50.08, 14.69, and 21.76 microg/mL against fourth-instar Aedes aegypti larvae.

Aedes↗
PubMed2006

Comparative susceptibility of European corn borer, southwestern corn borer, and sugarcane borer (Lepidoptera: Crambidae) to Cry1Ab protein in a commercial Bacillus thuringiensis corn hybrid.

One field strain each of the European corn borer, Ostrinia nubilalis (Hübner); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.); were collected from cornfields in northeastern Louisiana. Susceptibilities of the field strain and a corresponding laboratory strain of the three borer species to Cry1Ab protein in DK69-70 Bacillus thuringiensis (Bt) corn hybrid were determined by exposing neonates to intact leaf tissues from whorl stage plants or by feeding neonates or third instars on a meridic diet treated with different concentrations of Cry1lAb protein extracted from Bt corn leaves. Mortality and growth of larvae were evaluated after 2 and 4 d posttreatment in the bioassays by using intact leaf tissues or after 7 d in the bioassays by using diet incorporating Cry1Ab protein. D. saccharalis was the least susceptible species to Cry1Ab protein among the three species, followed by D. grandiosella, whereas O. nubilalis was most susceptible. The 2-d mortality of D. saccharalis neonates on intact Bt leaf tissues was lower than that of O. nubilalis and D. grandiosella. All neonates of O. nubilalis were killed on the diet treated with Cry1Ab protein at 0.5 and 1 mg/kg. The mortality of D. grandiosella was > 75% at 1 mg/kg, but it was < 6% for D. saccharalis at 1 mg/kg. The LC50 values of D. saccharalis were 3- and 11-fold higher than those of D. grandiosella and O. nubilalis, respectively. The LC90 values of D. saccharalis were 8- and 32-fold higher than those of D. grandiosella and O. nubilalis, respectively. Larval growth of the three species on Cry1Ab-treated diet was inhibited, but the inhibition was greater for O. nubilalis and D. grandiosella than for D. saccharalis. The lower susceptibility of D. saccharalis to Cry1Ab protein suggests that it is necessary to verify if a high-dose Bt corn for O. nubilalis and D. grandiosella is also a high dose for D. saccharalis.

Analysis of Variance↗