Susceptibility of Myzus persicae, Brevicoryne brassicae and Nasonovia ribisnigri to Fungal Biopesticides in Laboratory and Field Experiments.

The aim of this study was to evaluate the potential of entomopathogenic fungi (EPF) for the control of aphid pests of field vegetable crops. Four biopesticides based on the EPF Beauveria bassiana (Botanigard ES and Naturalis L), Cordyceps fumosorosea s.l. (Preferal WG), and Akanthomyces dipterigenus (Vertalec) were evaluated in a laboratory bioassay against peach-potato aphid Myzus persicae, cabbage aphid Brevicoryne brassicae, and currant-lettuce aphid Nasonovia ribisnigri. There was significant variation in the spore dose provided by the products, with Botanigard ES producing the highest dose (639 viable spores per mm2). Botanigard ES also caused more mortality than the other products. Combining Vertalec with the vegetable oil-based adjuvant Addit had an additive effect on the mortality of B. brassicae. All fungal products reduced the number of progeny produced by M. persicae but there was no effect with B. brassicae or N. ribisnigri. When aphid nymphs were treated with Botanigard ES and Preferal WG, both products reduced population development, with up to 86% reduction occurring for Botanigard ES against M. persicae. In a field experiment, Botanigard ES sprayed twice, at seven-day intervals, against B. brassicae on cabbage plants, reduced aphid numbers by 73%. In a second field experiment with B. brassicae, M. persicae, and N. ribisnigri, Botanigard ES reduced populations of B. brassicae and N. ribisnigri but there was no significant effect on M. persicae.

Investigating the potential of an autodissemination system for managing populations of vine weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae) with entomopathogenic fungi.

Vine weevil, also known as black vine weevil, (Otiorhynchus sulcatus) is an economically important pest affecting soft fruit and nursery stock in temperate regions. We used laboratory and polytunnel experiments to investigate a novel control system based on autodissemination of spores of an entomopathogenic fungus to populations of adult vine weevils. The fungus was applied as a conidial powder, used on its own or formulated with talc, to a simple plastic refuge for vine weevils. The potential for adult weevils to disseminate the fungus was investigated first in polytunnel experiments using fluorescent powders applied to the refuge in lieu of fungal conidia. In this system, 88% of adult weevils came in contact with the powder within 48 h. When the powder was applied to five adult weevils that were then placed within a population of 35 potential recipients, it was transmitted on average to 75% of the recipient population within 7 days. Three isolates of entomopathogenic fungi (Beauveria bassiana isolate codes 433.99 and 1749.11 and Metarhizium brunneum isolate code 275.86), selected from a laboratory virulence screen. These three isolates were then investigated for efficacy when applied as conidial powders in artificial refuges placed among populations of adult weevils held in experimental boxes in the laboratory at 20 °C. Under this regime, the fungal isolates caused 70-90% mortality of adult weevils over 28 days. A final polytunnel experiment tested the efficacy of conidial powders of M. brunneum 275.86 placed in artificial refuges to increase vine weevil mortality. Overall weevil mortality was relatively low (26-41%) but was significantly higher in cages in which the conidial powders were placed in refuge traps than in cages with control traps. The lower weevil mortality recorded in the polytunnel experiment compared to the laboratory test was most likely a consequence of the greater amounts of inoculum required to kill adult weevils when conditions fluctuate between favourable and unfavourable temperatures e.g. below 15 °C. The potential of an autodissemination system for entomopathogenic fungi as a means of controlling vine weevil as part of an integrated pest management programme is discussed.

A strong immune response in young adult honeybees masks their increased susceptibility to infection compared to older bees.

Honeybees, Apis mellifera, show age-related division of labor in which young adults perform maintenance ("housekeeping") tasks inside the colony before switching to outside foraging at approximately 23 days old. Disease resistance is an important feature of honeybee biology, but little is known about the interaction of pathogens and age-related division of labor. We tested a hypothesis that older forager bees and younger "house" bees differ in susceptibility to infection. We coupled an infection bioassay with a functional analysis of gene expression in individual bees using a whole genome microarray. Forager bees treated with the entomopathogenic fungus Metarhizium anisopliae s.l. survived for significantly longer than house bees. This was concomitant with substantial differences in gene expression including genes associated with immune function. In house bees, infection was associated with differential expression of 35 candidate immune genes contrasted with differential expression of only two candidate immune genes in forager bees. For control bees (i.e. not treated with M. anisopliae) the development from the house to the forager stage was associated with differential expression of 49 candidate immune genes, including up-regulation of the antimicrobial peptide gene abaecin, plus major components of the Toll pathway, serine proteases, and serpins. We infer that reduced pathogen susceptibility in forager bees was associated with age-related activation of specific immune system pathways. Our findings contrast with the view that the immunocompetence in social insects declines with the onset of foraging as a result of a trade-off in the allocation of resources for foraging. The up-regulation of immune-related genes in young adult bees in response to M. anisopliae infection was an indicator of disease susceptibility; this also challenges previous research in social insects, in which an elevated immune status has been used as a marker of increased disease resistance and fitness without considering the effects of age-related development.