Differential crop damage by healthy and nucleopolyhedrovirus-infected Mamestra brassicae L. (Lepidoptera: Noctuidae) larvae: a field examination

Baculovirus infection in Lepidoptera can alter both larval mobility and feeding rates, which can in turn affect pathogen transmission and dispersal in the field. We compared the damage to cabbage plants in the field caused by healthy and nucleopolyhedrovirus-infected Mamestra brassicae L. (Lepidoptera: Noctuidae) larvae released as second and fourth instars. There was no significant difference in plant consumption by healthy and infected larvae for the first 4 days after release. From day 5 onwards, infected larvae caused significantly less defoliation. This pattern was similar for larvae at both larval instars. Defoliation was greater for fourth instars throughout the experiment.     

Toxicities of 26 pesticides against 10 biological control species

To determine selective effectiveness for specific pesticides on biological control species we evaluated the contact toxicity of 16 insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides. Targeted species included 3 predatory mites (Phytoseiulus persimilis Athias-Henriot, Amblyseius swirskii Athias-Henriot, and Neoseiulus californicus McGregor), 5 hymenopteran parasitoids (Diglyphus isaea Walker, Aphidius colemani Viereck, Encarsia formosa Gahan, Eretmocerus eremicus Rose and Zolnerowich and E. mundus Mercet), and 2 hemipteran predators (Orius laevigatus Fieber and Nesidiocoris tenuis Reuter) in laboratory condition. In addition, residual toxicity was evaluated on P. persimilis, E. formosa, and O. laevigatus. For contact toxicity, five insecticides (spinetoram, spinosad, lepimectin, chlorfenapyr, and dinotefuran + spinetoram) showed high toxicity to predatory mites. Most pesticides tested were highly toxic to all hymenopteran species except for D. isaea which showed low susceptibility to 11 pesticides. Bistrifluron + flubendiamide and B. valismortis were less toxic to A. colemani, and only B. valismortis was safe to both E. mundus and E. eremicus. Insect growth regulators (methoxyfenozide and bistrifluron), chlorantraniliprole, and bistrifuron + flubendiamide were not toxic to hemipteran predators. Fungicides and biopesticides were safe to hemipteran predators except for two biopesticides (B. subtilis and P. fluorescens). Most pesticides had low residual toxicity to P. persimilis, with the exception of chlorfenapyr whose toxicity persisted over 7 days. One insecticide (cyantraniliprole), 2 acaricides (spiromesifen and fenpyroximate), 1 fungicide (metrafenone), and 4 biopesticides (B. subtilis, P. polymyxa, P. fluorescens, and B. valismortis) showed a much lower residual toxicity to E. formosa. Eight insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides showed low residual toxicity to O. laevigatus.     

Surface coating aids survival of Serratia entomophila (Enterobacteriaceae) in granules for surface application

The nonspore-forming bacterium Serratia entomophila may be used to control the New Zealand grass grub (Costelytra giveni) but is sensitive to environmental stress and must be formulated to improve survival. Existing formulations require subsurface application limiting the area that can be treated. Formulations that allow delivery by broadcast methods are desirable to reduce application costs and increase the potential for aerial application to inaccessible areas. Two formulations were prepared for use in experiments examining the persistence and movement of inoculum through soil. When granules were applied to the soil surface, bacterial survival was negligible in uncoated core, but improved with increasing thickness of the coating. Both survival of bacteria and release into the soil were influenced by soil moisture content. Granules at <12% soil moisture showed high bacterial mortality and reduced delivery to the soil, while at 28% soil moisture most bacteria were released to the soil. There was a high level of survival of the applied bacteria within granules at 20% and 28% soil moisture. The formulations maintained viability of S. entomophila in granules stored under ambient conditions for more than 6 months. In laboratory and field tests, the application of granules caused disease in the target grass grub larvae, whether application was applied to the surface or subsurface. In field trials, broadcast applied granules could produce equivalent disease to thin-coat granules drilled into the soil, but these levels of disease were associated with the occurrence of precipitation shortly after application.     

Potential of a Dried Mycelium Formulation of an Indigenous Strain of Metarhizium anisopliae Against Subterranean Pests of Cranberry

We demonstrated that a dried mycelium formulation of an indigenous strain of Metarhizium anisopliae has good potential as an effective biopesticide against the black vine weevil (BVW), Otiorhynchus sulcatus (F.), and the cranberry girdler (CG), Chrysoteuchia topiaria (Zeller). The formulation was produced at moderate sized batches scales (~ 100g product per batch) using inexpensive and easily obtainable equipment (< US$1000). Levels of conidiation were consistent among production batches and storage intervals with the product remaining viable for long time periods at 4&#176;C, in one case for more than a year. Levels of contamination by yeasts and other benign fungi were also consistent. Fewer BVW and CG were found in small plots treated with the dried mycelium formulation than in untreated plots, but differences were not always significant. A waxmoth ( Galleria mellonella ) bait bioassay demonstrated the formulation remained viable in the soil over long time periods (> 7 months). Percentage of M. anisopliae infected waxmoth larvae was significantly affected by rate.     

Effect of Application Time on the Efficacy of Sclerotinia sclerotiorum as a Mycoherbicide for Cirsium arvense Control in Pasture

An experiment was conducted in sheep-grazed pasture in three regions of New Zealand over three years to evaluate the effect of application time on the efficacy of a dry granule myceliumon-wheat formulation of Sclerotinia sclerotiorum for the biological control of Cirsium arvense . At each site, the experimental mycoherbicide was applied to a previously untreated plot in each month of the year for three years at a dose of 50 g m -2 . Applications made during the spring and early summer months of October, November and December significantly reduced the ground cover of C. arvense for 67, 67 and 44%, respectively of these applications. Reduced ground covers ranged from 38 to 81% of the cover on untreated plots. Applications in late summer and autumn were less effective. Correlations of ground cover by C. arvense with climate parameters suggested that free moisture promoted treatment efficacy, but that intense rainfall after treatment reduced efficacy through wash off. The importance of leaf wetness for the efficacy of the mycoherbicide was confirmed by comparing disease development and mortality in C. arvense shoots with and without enhanced moisture levels under field conditions. A water miscible formulation applied as a slurry was less dependent upon leaf wetness than the dry granule formulation.     

Microbial and viral chitinases: Attractive biopesticides for integrated pest management

The negative impact of the massive use of synthetic pesticides on the environment and on human health has stimulated the search for environment-friendly practices for controlling plant diseases and pests. Among them, biocontrol, which relies on using beneficial organisms or their products (bioactive molecules and/or hydrolytic enzymes), holds the greatest promise and is considered a pillar of integrated pest management. Chitinases are particularly attractive to this purpose since they have fungicidal, insecticidal, and nematicidal activities. Here, current knowledge on the biopesticidal action of microbial and viral chitinases is reviewed, together with a critical analysis of their future development as biopesticides.     

Insecticidal crystal proteins from native <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>: numerical analysis and biological activity against <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis>

Fourteen strains of Bacillus thuringiensis collected from both larvae showing disease symptoms and soil samples in northwest Argentina were characterized by insecticidal activity against Spodoptera frugiperda. First instar larvae and protein profile SDS-PAGE analysis of whole cell proteins not only allowed the differentiation of native Bacillus thuringiensis but also revealed the possibility of applying protein profile analysis in classification of toxicity patterns. Cluster analysis showed that there were two main groups. Interestingly, one of them only contained the most pathogenic native strains. The biomass-bound protease activity of native pathogenic isolates and the reference strain Bt 4D1 is also reported.     

Production of Choristoneura fumiferana Nucleopolyhedrovirus in C. fumiferana (CF-2C1 Cells) in a 3 Litre Bioreactor Using Serum-free Medium

The purpose of this study was to develop a cell culture process in a bioreactor for the production of a viral insecticide for the spruce budworm, Choristoneura fumiferana . Several cell lines were tested for their growth in serum-free medium suspension cultures. One cell line, CF-124T-2C1 (CF-2C1), was successfully adapted to grow in suspension cultures in SFM. Serum-free Ex-Cell 405 medium produced a much higher cell density (6.3 x 10 6 cells ml -1 ) than the Grace's medium supplemented with 10% fetal bovine serum (2.5 x 10 6 cells ml -1 ). Also, a higher yield of virus was obtained in the former medium. Ex-Cell 405, was used to study the growth of CF-2C1 cells and the production of C. fumiferana nucleopolyhedrovirus (CfMNPV) in a 3 l bioreactor. Under these conditions, a specific growth rate ( μ) of 0.027 h -1 was obtained during the exponential growth phase, and the specific carbon dioxide evolution rate, as determined by on-line measurement, was 0.9 x 10 -16 mol cell -1 s -1 and 1.78 x 10 -16 mol cell -1 s -1 during growth and infection phases, respectively. Virus production in bioreactor cultures infected at 1.3 x 10 6 cells ml -1 was consistently lower than that obtained in Erlenmeyer shake flasks. Only 26% of the cells were infected in the bioreactor compared to 44% in the shake flasks. However, a higher yield of occluded virus was obtained in the bioreactor cultures than in shake flasks. The production of occlusion bodies (OB) achieved in bioreactor cultures was 2 x 10 6 OB ml -1 .     

Quality Control of Fungal and Viral Biocontrol Agents - Assurance of Product Performance

An essential feature of the production of all microbial control agents is an effective quality control system. Well-defined product specifications with accompanying quality control procedures help to maximize product performance, ensure product safety, standardize manufacturing costs and reduce the risks of supply failure, thus building user confidence. A production system that does not have a quality control system is one whose output is uncontrolled and a lack of thorough quality feedback can result in batches of product with variable concentrations of active agent. This results in products with variable performance leading to control failures by users and serious loss of user confidence. Strict quality control procedures are not only essential for product consistency, but also for safety. Where quality control is inadequate, microbial contamination of the final product is inevitable. In most of such cases this will merely lead to a loss of efficacy due to dilution of the active ingredient by competing microorganisms, but also the potential of producing human pathogens must be ruled out. Recognition of contaminants and quantification of the degree of contamination are therefore important in determining any possible risk to human health. Many low technology production systems in use around the world have minimal or no quality control procedures. This is unacceptable and can damage the reputation of microbial control in addition to possibly posing health risks to those that produce or are exposed to the product. Two case studies from developing countries, are used to illustrate how the lack of quality control procedures can lead to the production of low viability, highly contaminated products with low or negligible concentrations of the active ingredient. However, it is also demonstrated that low technology production systems in developing countries can produce high quality products, provided appropriate quality control procedures are firmly implemented. It must be recognized that quality control procedures can be more complex and technologically demanding than the production procedures themselves, but it is largely on the effectiveness of these control procedures that the long-term acceptability of fungal and viral products depends. This paper details the quality control procedures considered necessary in the mass production of fungi and viruses for use as biocontrol agents, and attempts to suggest reasonable standards that can be achieved by all producers.     

Microbial control in Southeast Asia

Beginning in the 1980s, concerns about the deleterious effects of synthetic pesticides have driven a significant Southeast Asian research and development effort directed towards alternative pest control strategies, including the use of microbial control agents. Despite this effort, use of microbial control agents has grown slowly in the region. This is the result of an interplay between internal factors such as economics, national research programs, farmer education, manufacturing capabilities and regulatory frameworks, and external factors such as the influence of neighboring countries (particularly China), the availability of competitive pest control products, import regulations on pesticide residues and the activities of donor agencies. The role of these factors in providing both incentives and barriers to the adoption of microbial control are explored, and examples of promising projects are examined as a means of pointing the way forward towards increased progress in the future.