Contribution of biological control in management of water hyacinth

Biological control was foreseen as the long-term strategy for controlling water hyacinth in Uganda. Two species of weevils, Neochetina eichhorniae and Neochetina bruchi were imported into Uganda from Benin (West Africa) in 1993. A total of 600 weevils of each species were imported. The weevils were tested for specificity using key agricultural crops including maize, beans and bananas and were found to be water-hyacinth specific for their food and reproduction.

Mass rearing of Aphidius gifuensis (Hymenoptera : Aphidiidae) for biological control of Myzus persicae (Homoptera : Aphididae)

The green peach aphid, Myzus persicae, is a major pest of tobacco, Nicotiana tabacum, in Yunnan province, China, where its control still depends on the use of insecticides. In recent years, the local government and farmers have sought to improve the biological control of this tobacco pest. In this paper, we present methods for mass rearing Aphidius gifuensis, a dominant endoparasitoid of M. persicae on tobacco plants in this region. The tobacco cultivar K326 (N. tabacum) was used as the host plant and M. persicae as the host insect. In the greenhouse, we collected tobacco seedlings for about 35 days (i.e., until the six-true-leaf stage), transferred them to 7.5-cm diameter pots, and kept these plants in the greenhouse for another 18 days. These pots were then transferred to an insectary-greenhouse, where the tobacco seedlings were inoculated with five to seven wingless adult M. persicae per pot. After 3 days, the infested seedlings were moved to a second greenhouse to allow the aphid population to increase, and after an additional 4 +/- 1 days when 182 +/- 4.25 aphid adults and nymphs were produced per pot, they were inoculated with A. gifuensis. With this rearing system, we were able to produce 256 +/- 8.8 aphid mummies per pot, with an emergence rate of 95.6 +/- 2.45%; 69% were females. The daily cost of parasite production (recurring costs only) was US$ 0.06 per 1000 aphid mummies. With this technique, we released 109 800 parasitoids in 1998, 196 000 in 1999, 780 000 in 2000, and 5 600 000 in 2001 during a 2-month period each year This production method is discussed with respect to countrywide usage in biological control and integrated control of M. persicae.

Development and use of parasitoids (Hymenoptera : Aphidiidae & Aphelinidae) for biological control of aphids in China

A review of aphid parasitoids in China with special emphasis on their production, utilization, and conservation is presented with a brief history of Chinese biological control. Twenty genera, 99 species of Aphidiidae and two genera, 11 species of Aphelinidae were recorded in China. Each parasitoid is listed with a brief description of aphids, host plants, areas of study such as taxonomy, biology, bionomics, geographic distribution, rearing, and literature citations. Achievements, status, and problems in aphid parasitoid production, utilization, conservation, and future prospects are detailed for dominant aphid parasitoids such as Aphidius gifuensis Ashmead, A. ervi Haliday and Aphelinus mali Haldeman. Finally, opportunities and challenges of commercialization commercialization of natural enemies, especially aphid parasitoids, in China, are analyzed and discussed.

Vertical transmission efficiency and insecticidal properties of Spodoptera exigua Nucleopolyhedrovirus (SeMNPV) genotypes for their use in biological control

El nucleopoliedrovirus de Spodoptera exigua (SeMNPV) es un patógeno natural de las poblaciones larvarias de S. exigua que constituye la base de un bioinsecticida comercializado en España para el control biológico de esta plaga en pimiento. Recientes estudios han demostrado que la transmisión del virus a la descendencia (transmisión vertical) se da con frecuencia y podría ser una característica deseable para su uso en aplicaciones de campo. En el presente trabajo se discute la conveniencia de utilizar una mezcla de dos genotipos SeAl1 (transmisión vertical) y SeG25 (transmisión horizontal) en determinadas proporciones para mejorar las características que cada uno de ellos presenta por separado y así explotar cada una de las vías de transmisión. La patogenicidad (CL50) del genotipo SeG25, y de cualquiera de las mezclas que contienen un 25, 50 o 75 % del mismo, fue más alta que la del aislado SeAl1. Sin embargo, en términos de virulencia (TMM) y productividad (OBs/larva) no se observaron diferencias significativas entre genotipos ni entre sus mezclas. Además se evaluó la capacidad de producir infecciones encubiertas de cada genotipo y sus mezclas sometiendo larvas de S. exigua a infecciones subletales del virus. Se encontraron transcritos del virus para el gen temprano ie0 mediante RT-PCR en los adultos supervivientes a infecciones provocadas por el genotipo SeG25 y todas las mezclas. También se testaron otros dos genes virales que se expresan de manera temprana y tardía en la infección de baculovirus (DNA-polimerasa y polihedrina) para los que en ningún caso se detectaron transcritos.

The relationship between agricultural intensification and biological control: experimental tests across Europe

Agricultural intensification can affect biodiversity and related ecosystem services such as biological control, but large-scale experimental evidence is missing. We examined aphid pest populations in cereal fields under experimentally reduced densities of (1) ground-dwelling predators (-G), (2) vegetation-dwelling predators and parasitoids (-V), (3) a combination of (1) and (2) (-G-V),compared with open-fields (control), in contrasting landscapes with low vs. high levels of agricultural intensification (AI), and in five European regions. Aphid populations were 28%, 97%, and 199% higher in -G, -V, and -G -V treatments, respectively, compared to the open fields, indicating synergistic effects of both natural-enemy groups. Enhanced parasitoid : host and predator : prey ratios were related to reduced aphid population density and population growth. The relative importance of parasitoids and vegetation-dwelling predators greatly differed among European regions, and agricultural intensification affected biological control and aphid density only in some regions. This shows a changing role of species group identity in diverse enemy communities and a need to consider region-specific landscape management.

Persistent negative effects of pesticides on biodiversity and biological control potential on European farmland

During the last 50 years, agricultural intensification has caused many wild plant and animal species to go extinct regionally or nationally and has profoundly changed the functioning of agro-ecosystems. Agricultural intensification has many components, such as loss of landscape elements, enlarged farm and field sizes and larger inputs of fertilizer and pesticides. However, very little is known about the relative contribution of these variables to the large-scale negative effects on biodiversity. In this study, we disentangled the impacts of various components of agricultural intensification on species diversity of wild plants, carabids and ground-nesting farmland birds and on the biological control of aphids.

Biological control of the fish louse in a rainbow trout fishery

Novel egg-laying boards were found to be effective in the biological control of the freshwater fish louse Argulus foliaceus in a 12.9 ha rainbow trout Oncorhynchus mykiss fishery which had a high prevalence and intensity of infection of juvenile parasites in the early spring of 1999. Approximately 228 000d during an extensive 14 week period of egg laying which peaked in June 1999. In contrast, only 1566 clutches were harvested in 2000, when egg laying activity showed a bi-modal distribution, peaking in May and again in July and August. iaceus on rainbow trout in consecutive years was 2.9 : 1 and 2.1 : 1. Estimates of the size of the female A. foliaceus population based on egg-laying activity in 1999 exceeded that derived from measurements of prevalence and intensity of infection, whereas in 2000, this was more in balance. A minimum temperature of 10 degree C was identified for egg laying, which occurred continuously from May to October in a broadly synchronous manner.. Copyright 2002 The Fisheries Society of the British Isles

Bacteriophages of Erwinia amylovora and their potential use in biological control

Forty-four bacteriophage isolates of Erwinia amy/ovora, the causal agent of fire blight, were collected from sites in and around the Niagara Region of Southern Ontario in the summer of 1998. Phages were isolated only from sites where fire blight was present. Thirty-seven of these phages were isolated from the soil surrounding infected trees, with the remainder isolated from aerial plant tissue samples. A mixture of six E. amy/ovora bacterial host strains was used to enrich field samples in order to avoid the selection bias of a single-host system. Molecular characterization of the phages with a combination of peR and restriction endonuclease digestions showed that six distinct phage types were isolated. Ten phage isolates related to the previously characterized E. amy/ovora phage PEa1 were isolated, with some divergence of molecular markers between phages isolated from different sites. The host ranges of the phages revealed that certain types were unable to efficiently lyse some E. amy/ovora strains, and that some types were able to lyse the epiphytic bacterium Pantoea agg/omerans. Biological control of E. amy/ovora by the bacteriophages was assessed in a bioassay using discs of immature pear fruit. Twenty-three phage isolates were able to significantly suppress the incidence of bacterial exudate on the pear disc surface. Quantification of the bacterial population remaining on the disc surface indicated that population reductions of up to 97% were obtainable by phage treatment, but that elimination of bacteria from the surface was not possible with this model system.

Antibody Based Diagnostic for Detection Of Vibrios and their Biological Control using Antagonistic Bacteria in Macrobrachium Rosenbergii Larval Rearing Systems

The main objective of the work undertaken here was to develop an appropriate microbial technology to protect the larvae of M.rosenbergii in hatchery from vibriosis. This technology precisely is consisted of a rapid detection system of vibrios and effective antagonistic probiotics for the management of vibrios. The present work was undertaken with the realizations that to stabilize the production process of commercial hatcheries an appropriate, comprehensive and fool proof technology is required primarily for the rapid detection of Vibrio and subsequently for its management. Nine species of Vibrio have been found to be associated with larvae of M. rosenbergii in hatchery. Haemolytic assay of the Vibrio and Aeromonas on prawn blood agar showed that all isolates of V. alginolyticus and Aeromonas sp., from moribund, necrotized larve were haemolytic and the isolates of V.cholerae, V.splendidus II, V.proteolyticus and V.fluvialis from the larvae obtained from apparently healthy larval rearing systems were non-haemolytic. Hydrolytic enzymes such as lipase, chitinase and gelatinase were widespread amongst the Vibrio and Aeromonas isolates. Dominance of V.alginolyticus among the isolates from necrotic larvae and the failure in isolating them from rearing water strongly suggest that they infect larvae and multiply in the larval body and cause mortality in the hatchery. The observation suggested that the isolate V. alginolyticus was a pathogen to the larvae of M.rosenbergii. To sum up, through this work, nine species of Vibrio and genus Aeromonas associated with M.rosenbergii larval rearing systems could be isolated and segregated based on the haemolytic activity and the antibodies (PA bs) for use in diagnosis or epidemiological studies could be produced, based on a virulent culture of V.alginolyticus. This could possibly replace the conventional biochemical tests for identification. As prophylaxis to vibriosis, four isolates of Micrococcus spp. and an isolate of Pseudomonas sp. could be obtained which could possibly be used as antagonistic probiotics in the larval rearing system of M.rosenbergii.

Characterization and mechanism of action of the biological control agent Pantoea agglomerans EPS125

La soca EPS125 ha mostrat ser un efectiu agent de control biològic de diferents patògens fúngics de postcollita en diferents fruits. Degut a la seva elevada eficàcia, es va plantejar desenvolupar aquesta soca comercialment i per aquest motiu en el present treball es plantejà complementar la informació necessària pel seu registre. D'acord amb els resultats obtinguts mitjançant proves fenotípiques i genotípiques, la soca EPS125 queda inclosa dins l'espècie Pantoea agglomerans (Enterobacter agglomerans-Erwinia herbicola). En relació a la utilització de fonts de carboni, en el perfil i contingut d'àcids grassos cel·lulars i en el polimorfisme en la longitud dels fragments de macrorestricció genòmica (MRFLP), la soca EPS125 mostrà trets característics que la diferencien d'altres soques. Els dos marcadors moleculars (125.2 i 125.3) específics per la soca EPS125 dissenyats en el present treball mostraren ser semiespecífics per la seva detecció mitjançant la tècnica PCR i Real Time PCR. Quedant pendent l'anàlisi d'especificitat de l'ús combinat dels dos marcadors moleculars en una reacció PCR multiplex. P. agglomerans EPS125 ha mostrat ser molt efectiva en el control de Penicillium expansum en poma amb una dosi efectiva mitjana de 2.7x105 a 7x105 ufc/ml, i una ratio de 25-101 cèl·lules de la soca EPS125 per inactivar una espora del patogen segons el model de saturació hiperbòlica. Segons les aproximacions fenotípiques i estudis genotípics realitzats, sembla que els mecanismes de biocontrol utilitzats per la soca EPS125 contra P. expansum en poma estan directament relacionats amb la capacitat de formació de biofilm per aquesta soca.