We previously demonstrated that exposure to febrile-range hyperthermia (FRH) accelerates pathogen clearance and increases survival in murine experimental Klebsiella pneumoniae peritonitis. However, FRH accelerates lethal lung injury in a mouse model of pulmonary oxygen toxicity, suggesting that the lung may be particularly susceptible to injurious effects of FRH. In the present study, we tested the hypothesis that, in contrast with the salutary effect of FRH in Gram-negative peritonitis, FRH would be detrimental in multilobar Gram-negative pneumonia. Using a conscious, temperature-clamped mouse model and intratracheal inoculation with K. pneumoniae Caroli strain, we showed that FRH tended to reduce survival despite reducing the 3 day-postinoculation pulmonary pathogen burden by 400-fold. We showed that antibiotic treatment rescued the euthermic mice, but did not reduce lethality in the FRH mice. Using an intratracheal bacterial endotoxin LPS challenge model, we found that the reduced survival in FRH-treated mice was accompanied by increased pulmonary vascular endothelial injury, enhanced pulmonary accumulation of neutrophils, increased levels of IL-1β, MIP-2/CXCL213, GM-CSF, and KC/CXCL1 in the bronchoalveolar lavage fluid, and bronchiolar epithelial necrosis. These results suggest that FRH enhances innate host defense against infection, in part, by augmenting polymorphonuclear cell delivery to the site of infection. The ultimate effect of FRH is determined by the balance between accelerated pathogen clearance and collateral tissue injury, which is determined, in part, by the site of infection.

The susceptibility of tomato stems to infection by Botrytis cinerea and the influence of temperature and humidity on disease development were investigated with stem pieces and whole plants. Stem rotting resulted after inoculation of wounded stems with a conidial suspension in water or with dry conidia; no symptoms developed following inoculation of unwounded stems. The proportion of inoculated stems developing Botrytis rot increased as the inoculum concentration was increased from 10 to 10,000 conidia per stem. Stem susceptibility to infection declined from 60 to 8% as wound age increased from 0 to 24 h before inoculation. Wounded stem pieces maintained in a low vapor pressure deficit (VPD) environment (<0.2 kPa) remained susceptible for a longer period than those maintained at a high VPD. Infection and stem rotting occurred at temperatures of 5 to 26°C, with disease development most rapid at 15°C. Sporulation was optimal at 15°C and did not occur within 20 days of incubation at 5 or 26°C. Incubation at high humidity following inoculation of fresh wounds (VPD <0.2 kPa) did not increase infection incidence or tissue rotting, compared with incubation at a VPD >1.3 kPa; however, incubation at the lower VPD did increase the intensity of sporulation.

Two bacterial isolates, Bacillus megaterium (c96) and Burkholderia cepacia (c91), demonstrated to be antagonistic against Fusarium oxysporum f.sp. radicis-lycopersici , the causal organism of fusarium crown and root rot of tomato, were evaluated as biocontrol agents alone and when integrated with the fungicide carbendazim. In an initial screening, these isolates reduced disease incidence by 75 and 88%, respectively. In vitro , both biocontrol agents were highly tolerant to the fungicide carbendazim, commonly used to control fusarium diseases. Carbendazim reduced disease symptoms by over 50% when used at > 50 µ g mL − 1 , but had little effect at lower concentrations. Combination of the bacterial isolates and carbendazim gave significant ( P ≤ 0·05) control of the disease when plants were artificially inoculated with the pathogen. Application of carbendazim at a low concentration (1 µ g mL − 1 ) in combination with B. cepacia c91 reduced disease symptoms by 46%, compared with a reduction of 20% obtained with the bacterium alone and no control with the chemical treatment alone. A combination of B. megaterium c96 with an increased application rate of 10 µ g mL − 1 carbendazim significantly reduced disease symptoms by 84% compared with inoculated controls and by 77% compared with carbendazim treatment alone. In this experiment, the integrated treatment also slightly outperformed application of 100 µ g mL − 1 carbendazim, and bacteria applied without fungicide also provided good disease control.

Plants possess anti-herbivore defences that could be exploited for crop protection. The potential for deploying physical defence traits for more sustainable pest management (i.e. reduced pesticide application) has not been fully realised. Using a perennial crop (red raspberry, Rubus idaeus), we take the novel approach of quantifying within-and between-genotype variation in a resistance trait, leaf trichome density, to determine precisely the effect of trichomes on host plant preference and suitability for two shoot-feeding arthropods, the European large raspberry aphid (Amphorophora idaei) and two-spotted spider mite (Tetranychus urticae). Additionally, we tested whether this trait influenced searching behaviour of a generalist herbivore predator (lacewing larvae, Chrysoperla carnea). Although there was no consistent genotypic variation in R. idaeus suitability for T. urticae, our hypothesis that T. urticae would avoid high leaf trichome density was supported on certain genotypes. The deterrent effect was mainly on egg deposition rather than leaf selection by adults, with up to sixfold differences in leaf preference depending on the genotypes offered. By contrast, there was significant genotypic variation in R. idaeus suitability for A. idaei (10-fold variation in aphid abundance), but, contrary to our prediction, aphid preference and infestation levels were unrelated to leaf trichome density. Instead, A. idaei performed best on vigorous genotypes, indicating that plant tolerance traits contributed to R. idaeus suitability for aphids. Leaf trichomes had little effect on the behaviour of the beneficial control agent C. carnea larvae. We conclude that physical anti-herbivore defences, specifically leaf trichomes, could be deployed to deter particular arthropod pests. However, the mechanistic approach adopted here is necessary to avoid antagonistic effects on other pests or on natural enemies.

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