The control of Norway rat populations on farms in the UK currently relies heavily on the use of anticoagulant rodenticides, and many infestations are safely and effectively controlled in this way. However, rodenticide use can represent a risk to non-target animals, and the emergence of 'hotspots' of resistance to anticoagulant rodenticides has led to concerns over the long-term viability of a rodenticide-biased approach. This study investigated some non-rodenticide approaches to rat control on farms. Small mammals potentially compete with rats for resources, and managing the habitat to encourage them could indirectly solve rat problems. Field margin surveys were conducted to examine the distribution of small mammals, and identify habitat characteristics that are associated with rat populations. The results were inconclusive, although there was some evidence that dense ground vegetation favours some small mammal species and discourages rat colonisation. In later trials, reducing cover and harbourage around farm buildings reduced rat activity and survival, and compared well with rodenticide use in terms of efficacy and labour input. By reducing cover around farm buildings, good results were achieved within a short space of time. However, the technique is likely to be more useful as part of a long term strategy, whereby greater consideration is given to making the farm environment less suitable for rats, without reducing the quality of the habitat for other species. It is unlikely that a resource management approach would not include the use of other methods, including limited use of traps and rodenticides where necessary. However, less emphasis on rodenticides could potentially offer long-term benefits in the form of reduced risks to non-target wildlife and help to limit the spread of resistant rat populations.

The incidence, influencing factors and mechanisms of resistance to insecticides from a range of chemical groups were examined in UK and European populations of the glasshouse whitefly, Trialeurodes vaporariorum (Westwood). Toxicological assessments of populations from a range of plant production glasshouses and comparisons with the responses of a laboratory susceptible strain disclosed levels of resistance to pyrethroid, organophosphate, insect growth regulator (IGR) and neonicotinoid insecticides. Responses to conventional compounds indicated varying levels of resistance, potentially reflecting disparate usage between collection sites. All strains examined possessed resistance to the IGR, buprofezin; some populations were virtually immune to this commonly used control agent. Selection experiments demonstrated reciprocal crossresistance between buprofezin and a further IGR, teflubenzuron, both of which are frequently incorporated into integrated pest management (IPM) programmes for this species. Results for the leading neonicotinoid, imidacloprid, revealed resistance in both UK and European strains, representing the first documented cases of neonicotinoid resistance in this species worldwide, and the first in any insect species within the UK. The lethal effects of vapour emitted by applications of buprofezin and the anti-feedant effects of imidacloprid were demonstrated in T. vaporariorum for the first time. The potential consequences of these factors for both the control and selection of resistance were highlighted. Mechanistic studies using electrophoresis and kinetic spectrophotometer readings showed that neither non-specific esterases nor modified acetylcholinesterases were involved with resistance to either pyrethroid or specific organophosphate insecticides.