An immunohistochemical study was conducted to detect the temporal infection sequence of Autographa californica M nuclear polyhedrosis virus in Trichoplusia ni larvae. Staining patterns indicated that the initial infection occurred in the midgut, simultaneously in columnar epithelial and regenerative cells, but that subsequently this tissue recovered. A major envelope glycoprotein stained in a polar fashion when it was expressed in columnar epithelial cells, but not when expressed in other cells types. Systemic infection was mediated by free virus for some tissues whereas infected hemocytes appeared to spread virus to other tissues by an unknown mechanism. A cell to cell spread within several tissues was detected. These results have important implications for baculoviruses engineered for improving their pesticide potential.

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is one of the most destructive cosmopolitan insect pests of brassicaceous crops. It was the first crop insect reported to be resistant to DDT and now, in many crucifer producing regions, it has shown significant resistance to almost every synthetic insecticide applied in the field. In certain parts of the world, economical production of crucifers has become almost impossible due to insecticidal control failures. Consequently, increased efforts worldwide have been undertaken to develop integrated pest management (IPM) programs, principally based on manipulation of its natural enemies. Although over 130 parasitoid species are known to attack various life stages of DBM, most control worldwide is achieved by relatively few hymenopteran species belonging to the ichneumonid genera Diadegma and Diadromus , the braconid genera Microplitis and Cotesia , and the eulophid genus Oomyzus . DBM populations native to different regions have genetic and biological differences, and specific parasitoid strains may be associated with the specific DBM strains. Therefore, accurate identification based on genetic studies of both host and parasitoid is of crucial importance to attaining successful control of DBM through inoculative or inundative releases. Although parasitoids of DBM larvae and pupae are currently its principal regulators, bacteria-derived products (e.g., crystal toxins from Bacillus thuringiensis ) and myco-insecticides principally based on Zoophthora radicans and Beauveria bassiana are increasingly being applied or investigated for biological control. Viruses, nematodes and microsporidia also have potential as biopesticides for DBM. When an insect pest is exposed to more than one mortality factor, there is the possibility of interactions that can enhance, limit, or limit and enhance the various aspects of effectiveness of a particular control tactic. This paper reviews the effectiveness of various parasitoids and entomopathogens against DBM, interactions among them, and their possible integration into modern IPM programs.

No abstract

Wolbachia are obligate intracellular bacteria which commonly infect arthropods. They are maternally inherited and capable of altering host development, sex determination, and reproduction. Reproductive manipulations include feminization, male-killing, parthenogenesis, and cytoplasmic incompatibility. The mechanism by which Wolbachia avoid destruction by the host immune response is unknown. Generation of antimicrobial peptides (AMPs) and reactive oxygen species (ROS) by the host are among the first lines of traditional antimicrobial defense. Previous work shows no link between a Wolbachia infection and the induction of AMPs. Here we compare the expression of protein in a cell line naturally infected with Wolbachia and an identical cell line cured of the infection through the use of antibiotics. Protein extracts of each cell line were analyzed by two dimensional gel electrophoresis and LC/MS/MS. Our results show the upregulation of host antioxidant proteins, which are active against ROS generated by aerobic cell metabolism and during an immune response. Furthermore, flow cytometric and microscopic analysis demonstrates that ROS production is significantly greater in Wolbachia-infected mosquito cells and is associated with endosymbiont-containing vacuoles located in the host cell cytoplasm. This is the first empirical data supporting an association between Wolbachia and the insect antioxidant system.

Summary1. Plant genotypic diversity has important consequences for a variety of ecosystem processes, yet empirical evidence for its effects on productivity, one of the most fundamental of these processes, is lacking. In addition, the performance of insect herbivores in response to high genotypic diversity is unknown, despite previous work demonstrating differential herbivore performance among plant genotypes. 2. We manipulated genotypic diversity of the annual plant Arabidopsis thaliana in both the presence and absence of the generalist herbivore Trichoplusia ni under semi-natural growth conditions. We used nine genotypes (eight ecotypes and one mutant) of A. thaliana known to differ widely in functional traits. Productivity and insect biomass were measured in monocultures and mixtures of all nine genotypes grown at multiple fertilization levels and planting densities. 3. In both the absence and presence of herbivores, genotypic diversity increased plant productivity and survival. This effect was, for the most part, independent of fertility or density. Sampling or selection effects did not appear to be wholly responsible for these results as all genotypes were maintained in equal proportion and no single genotype became dominant for the duration of the experiment. 4. High diversity increased T. ni biomass and survival in all treatments. Insect biomass was positively, but not tightly, correlated to plant biomass, indicating that the higher herbivore performance observed in genotypic mixtures was only partially due to higher productivity. 5. Synthesis. Our data support the idea that even within a single plant species, genotypic diversity can exert strong influences on both the producer and herbivore communities. The exact mechanisms responsible for these effects and the relative importance of genotypic diversity in natural communities warrant further investigation.