Richard T. Cook

Slug preferences for winter wheat cultivars and common agricultural weeds

1. Slugs are a serious pest of many crops, including winter wheat, but current methods of control are unreliable. As part of research study into the possibility that alternative food sources may reduce slug damage to winter wheat crops, the relative palatabilities to field slugs (Deroceras reticulatum) of different wheat cultivars and common agricultural weeds were examined. 2. Individual slugs were given one of 12 winter wheat cultivars for 72h, either as seeds, germinating seeds or young leaves. Individual slugs differed considerably in the amounts of wheat eaten, but there was no clear correlation between slug weight and amount consumed. The slugs did not exhibit any preferences for cultivars at any stage of development. 3. When individual slugs were offered a choice of the leaves of one of 12 common weeds together with wheat leaves, they manifested a hierarchy of preferences for the weeds, some of which were preferred to the wheat leaves. There was some evidence to suggest that when slugs were exposed to less preferred weeds, they consumed less overall, but they ate more wheat than slugs given palatable weed species. 4. The results indicate that the choice of wheat cultivar would not affect levels of slug damage. Weeds could potentially act as a readily available source of alternative food for slugs in the field as part of an integrated pest management programme for slugs. However, because weeds vary considerably in their palatability to slugs, the degree of protection afforded to a wheat crop would depend on the palatability of the weed species present.

The potential for common weeds to reduce slug damage to winter wheat: laboratory and field studies

1. Slugs are serious pests of winter wheat crops in temperate climates, but current methods of chemical control are often unreliable. This paper investigates the potential for common agricultural broad-leaved weeds to act as an alternative food source for slugs, thereby reducing damage to the crop, as part of an integrated approach to pest slug management in wheat crops. 2. An experiment carried out in the field examined the relative effectiveness of metaldehyde pellets and three weed species in reducing damage to wheat seeds and seedlings. Treatments were carried out in open-topped arenas, each containing eight adult field slugs Deroceras reticulatum. The presence of weeds that were palatable to slugs did limit damage to the crop but, over a 72-h period, metaldehyde provided the most effective level of control. 3. A laboratory experiment was carried out to study the feeding behaviour of the slugs in more detail. A single slug was placed in an arena containing food items attached to electronic probes that could detect bites by a slug. The presence of dandelion Taraxacum officinale leaves, a palatable species, reduced the number of wheat seeds damaged, but chickweed Stellaria media leaves, which are less palatable to slugs, had no effect. Most slugs ate the first food item encountered. When dandelion was eaten first, significantly fewer wheat seeds were damaged, and slugs subsequently took fewer bites on seeds than when either a seed or chickweed was eaten first. Slugs were more likely to ignore wheat seeds after a meal on dandelion. 4. Metaldehyde pellets tend to degrade a few days after application. It is suggested that weeds could provide an on-going degree of protection to the crop after the pellets have degraded and until the wheat plants have developed beyond the vulnerable stages. However, the importance of the palatability of the weeds to slugs, and a high weed density to ensure an early encounter with a weed plant during a foraging session, are highlighted by the laboratory study.

Unravelling the riddle of Radix: DNA barcoding for species identification of freshwater snail intermediate hosts of zoonotic digeneans and estimating their inter-population evolutionary relationships

Radix spp. are intermediate host snails for digenean parasites of medical and veterinary importance. Within this genus, species differentiation using shell and internal organ morphology can result in erroneous species identification, causing problems when trying to understand the population biology of Radix. In the present study, DNA barcoding, using cox1 and ITS2 sequences, identified populations of Radix auricularia and Radix balthica from specimens originally morphologically identified as Radix peregra from the UK. Assessment of cox1 and ITS2 as species identification markers showed that, although both markers differentiated species, cox1 possessed greater molecular diversity and higher phylogenetic resolution. Cox1 also proved useful for gaining insights into the evolutionary relationships of Radix species populations. Phylogenetic analysis and haplotype networks of cox1 indicated that R. auricularia appeared to have invaded the UK several times; some haplotypes forming a distinct UK specific clade, whilst others are more akin to those found on mainland Europe. This was in contrast to relationships between R. balthica populations, which had low molecular diversity and no distinct UK specific haplotypes, suggesting recent and multiple invasions from mainland Europe. Molecular techniques therefore appear to be crucial for distinguishing Radix spp., particularly using cox1. This barcoding marker also enables the population biology of Radix spp. to be explored, and is invaluable for monitoring the epidemiology of fluke diseases especially in the light of emerging diseases and food security.

Identification of a major causative agent of human cercarial dermatitis, Trichobilharzia franki (Müller and Kimmig 1994), in southern England and its evolutionary relationships with other European populations

BackgroundTrichobilharzia is the most species rich and widely distributed genus of schistosomes and is known throughout Europe and North America as an agent of human cercarial dermatitis. The disease is caused by an acute allergic reaction in the skin that develops as a consequence of repeated contact with water containing schistosomatid cercariae. However, despite historical outbreaks of the disease, there are no published records of accurately identified Trichobilharzia species from the UK.MethodsTwo hundred Radix auricularia (L.) were sampled from a recreational fishing lake in Hampshire and emerging schistosomatid cercariae were collected for microscopy and DNA extraction. General morphological description of the cercariae was performed, alongside sequencing and phylogenetic analysis of the 28S ribosomal DNA for accurate species identification as well as comparisons of ITS1 in order to identify evolutionary affinities with other European populations. All molecular comparisons were performed using published sequences.ResultsThe phylogenetic analysis of 28S sequences identified the cercariae as Trichobilharzia franki. Two unique British ITS1 haplotypes were identified which were most closely related to haplotypes of T. franki populations from France. Haplotype network analysis indicated the mixing of T. franki populations throughout Europe. It is suggested that parasite distribution is the probable result of the movement of migratory waterfowl.ConclusionsThis is the first accurate record of T. franki in the UK. The movement of T. franki with waterfowl could pose a considerable human health risk, as in mainland Europe, and signifies T. franki-associated human cercarial dermatitis as a re-emerging disease in the UK.

Correia Repeat Enclosed Elements and Non-Coding RNAs in the Neisseria Species

Neisseria gonorrhoeae is capable of causing gonorrhoea and more complex diseases in the human host. Neisseria meningitidis is a closely related pathogen that shares many of the same genomic features and virulence factors, but causes the life threatening diseases meningococcal meningitis and septicaemia. The importance of non-coding RNAs in gene regulation has become increasingly evident having been demonstrated to be involved in regulons responsible for iron acquisition, antigenic variation, and virulence. Neisseria spp. contain an IS-like element, the Correia Repeat Enclosed Element, which has been predicted to be mobile within the genomes or to have been in the past. This repeat, present in over 100 copies in the genome, has the ability to alter gene expression and regulation in several ways. We reveal here that Correia Repeat Enclosed Elements tend to be near non-coding RNAs in the Neisseria spp., especially N. gonorrhoeae. These results suggest that Correia Repeat Enclosed Elements may have disrupted ancestral regulatory networks not just through their influence on regulatory proteins but also for non-coding RNAs.