No abstract

The industrialization of livestock production and the widespread use of nontherapeutic antimicrobial growth promotants has intensified the risk for the emergence of new, more virulent, or more resistant microorganisms. These have reduced the effectiveness of several classes of antibiotics for treating infections in humans and livestock. Recent outbreaks of virulent strains of influenza have arisen from swine and poultry raised in close proximity. This working group, which was part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards—Searching for Solutions, considered the state of the science around these issues and concurred with the World Health Organization call for a phasing-out of the use of antimicrobial growth promotants for livestock and fish production. We also agree that all therapeutic antimicrobial agents should be available only by prescription for human and veterinary use. Concern about the risk of an influenza pandemic leads us to recommend that regulations be promulgated to restrict the co-location of swine and poultry concentrated animal feeding operations (CAFOs) on the same site and to set appropriate separation distances.

No abstract

Phytoviruses including tospoviruses are known to affect the behavior and fitness of their vectors both positively and negatively. In this study, we investigated the effects of Tomato spotted wilt virus (TSWV) (family Bunyaviridae, genus Tospovirus) infection on the fitness and feeding ability of tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) using peanut, Arachis hypogaea L. (Fabaceae), as a host. Potentially viruliferous F. fusca laid more eggs than non‐viruliferous F. fusca. In contrast, fewer potentially viruliferous F. fusca developed into adults and required a longer developmental time than non‐viruliferous F. fusca, indicating a direct negative effect of the virus on thrips fitness. In addition, no‐choice feeding tests indicated that non‐viruliferous F. fusca fed more rapidly than potentially viruliferous F. fusca. Typically, phytovirus infections are known to enhance the availability of vital nutrients such as free amino acids in infected host plants and to affect other important physiological processes negatively. Free amino acids are known to play a vital role in egg production and development. Further investigations in this study revealed that leaflets of infected plants had ca. 15 times more free amino acids than non‐infected leaflets. TSWV‐infected leaflets were used to rear potentially viruliferous thrips. Higher amino acid levels in TSWV‐infected leaflets than in non‐infected leaflets could have contributed to increased oviposition by potentially viruliferous F. fusca compared to non‐viruliferous F. fusca. Taken together, these results suggest that increased concentrations of free amino acids in TSWV‐infected plants might serve as an incentive for thrips feeding on otherwise unsuitable hosts, thereby facilitating TSWV acquisition and transmission.

Tomato spotted wilt virus (TSWV) severely affects peanut production in the southeastern United States. Breeding efforts over the last three decades resulted in the release of numerous peanut genotypes with field resistance to TSWV. The degree of field resistance in these genotypes has steadily increased over time, with recently released genotypes exhibiting a higher degree of field resistance than older genotypes. However, most new genotypes have never been evaluated in the greenhouse or laboratory against TSWV or thrips, and the mechanism of resistance is unknown. In this study, TSWV-resistant and -susceptible genotypes were subjected to TSWV mechanical inoculation. The incidence of TSWV infection was 71.7 to 87.2%. Estimation of TSWV nucleocapsid (N) gene copies did not reveal significant differences between resistant and susceptible genotypes. Parsimony and principal component analyses of N gene nucleotide sequences revealed inconsistent differences between virus isolates collected from resistant and susceptible genotypes and between old (collected in 1998) and new (2010) isolates. Amino acid sequence analyses indicated consistent differences between old and new isolates. In addition, we found evidence for overabundance of nonsynonymous substitutions. However, there was no evidence for positive selection. Purifying selection, population expansion, and differentiation seem to have influenced the TSWV populations temporally rather than positive selection induced by host resistance. Choice and no-choice tests indicated that resistant and susceptible genotypes differentially affected thrips feeding and survival. Thrips feeding and survival were suppressed on some resistant genotypes compared with susceptible genotypes. These findings reveal how TSWV resistance in peanut could influence evolution, epidemiology, and management of TSWV.

This study describes the identification of an aggregation pheromone for the pepper weevil,Anthonomus eugenii and field trials of a synthetic pheromone blend. Volatile collections and gas chromatography revealed the presence of six male-specific compounds. These compounds were identified using chromatographic and spectral techniques as: (Z)-2-(3,3-dimethylcyclohexylidene)ethanol, (E)-2-(3,3-dimethylcyclohexylidene)ethanol, (Z)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-(3,3-dimethylcyclohexylidene)acetaldehyde, (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid), and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol). The emission rates of these compounds from feeding males were determined to be about: 7.2, 4.8, 0.45, 0.30, 2.0, and 0.30µg/male/day, respectively. Sticky traps baited with a synthetic blend of these compounds captured more pepper weevils (both sexes) than did unbaited control traps or pheromone-baited boll weevil traps. Commercial and laboratory formulations of the synthetic pheromone were both attractive. However, the commercial formulation did not release geranic acid properly, and geranic acid is necessary for full activity. The pheromones of the pepper weevil and the boll weevil are compared. Improvements for increasing trap efficiency and possible uses for the pepper weevil pheromone are discussed. A convenient method for purifying geranic acid is also described.

Four studies were conducted in Georgia during spring 1999, 2000, 2001, and 2002 to evaluate various management tactics for reducing thrips and thrips-vectored tomato spotted wilt virus (TSWV) in tomato and their interactions relative to fruit yield. Populations of thrips vectors of TSWV, Frankliniella occidentalis (Pergande) and Frankliniella fusca (Hinds), were determined using flower and sticky trap samples. The management practices evaluated were host plant resistance, insecticide treatments, and silver or metallic reflective mulch. Averaged over all tests, the TSWV-resistant tomato 'BHN444' on silver mulch treatment had the largest effect in terms of reducing thrips and spotted wilt and increasing marketable yield. Of the insecticide treatments tested, the imidacloprid soil treatment followed by early applications of a thrips-effective foliar insecticide treatment provided significant increase in yield over other treatments. Tomato yield was negatively correlated with the number of F. fusca and percentage of TSWV incidence. F. occidentalis per blossom was positively correlated with percentage of TSWV incidence, but not with yield. No significant interactions were observed between cultivar reflective mulch main plot treatments and insecticide subplot treatments; thus, treatment seemed to be additive in reducing the economic impact of thrips-vectored TSWV. Control tactics that manage thrips early in the growing season significantly increased tomato yield in years when the incidence of TSWV was high (>17%).

Environmental pests may serve as reservoirs and vectors of zoonotic pathogens to leafy greens; however, it is unknown whether insect pests feeding on plant tissues could redistribute these pathogens present on the surface of leaves to internal sites. This study sought to differentiate the degree of tissue internalization of Escherichia coli O157:H7 when applied at different populations on the surface of lettuce and spinach leaves, and to ascertain whether lettuce-infesting insects or physical injury could influence the fate of either surface or internalized populations of this enteric pathogen. No internalization of E. coli O157:H7 occurred when lettuce leaves were inoculated with 4.4 log CFU per leaf, but it did occur when inoculated with 6.4 log CFU per leaf. Internalization was statistically greater when spinach leaves were inoculated on the abaxial (underside) than when inoculated on the adaxial (topside) side, and when the enteric pathogen was spread after surface inoculation. Brief exposure (∼18 h) of lettuce leaves to insects (5 cabbage loopers, 10 thrips, or 10 aphids) prior to inoculation with E. coli O157:H7 resulted in significantly reduced internalized populations of the pathogen within these leaves after approximately 2 weeks, as compared with leaves not exposed to insects. Surface-contaminated leaves physically injured through file abrasions also had significantly reduced populations of both total and internalized E. coli O157:H7 as compared with nonabraded leaves 2 weeks after pathogen exposure.