No abstract

SUMMARY The resistance to pirimicarb of populations of Aphis gossypii Glover from several glasshouses in England was studied in the laboratory by topical applications of insecticide and by electrophoresis and isoelectric focusing of aphid esterases. When compared with a known susceptible population, the aphids were found to be resistant to pirimicarb. Esterase patterns produced from resistant populations by poly‐acrylamide gel and starch gel electrophoresis and by isoelectric focusing consistently differed in both numbers of bands and migration rates from the susceptible type. Resistant A. gossypii were found infesting only chrysanthemums and would not transfer to cucumber, the host of the susceptible population.

Individual chrysanthemum cuttings and leaves infested with eggs and larvae of the alien leaf miner Liriomyza trifolii, and batches of pupae, were treated in the laboratory to find an effective quarantine treatment to control the pest in imported cuttings. The laboratory tests were based on a statutory quarantine treatment of 2 days' cold storage at 1-2°C followed by methyl bromide fumigation at 15°C with a concentration time product (CTP) of 54 g h/m3, which is used to control Spodoptera littoralis on imported chrysanthemum cuttings. Treatments of 2 days' storage at 1-2°C followed by methyl bromide fumigation at 15°C with a range of CTPs were used to obtain accurate dose-response lines and estimate the LD99 and LD99.9 for each stage of L. trifolii. The largest estimates of the LD99 for eggs, larvae and pupae up to 3 days old were 40.04, 34.49 and 42.64 g h/m3 respectively. These results indicate that the Spodoptera treatment should give high levels of kill of most stages of L. trifolii. However, the LD99 values for pupae more than 3 days old were greater than those for eggs, larvae and young pupae. Therefore if this treatment were adopted as a quarantine measure against L. trifolii, good prophylactic treatments and rigorous pre-packing inspections in exporting countries would need to be maintained, to minimise any risk of importing pupae. It would also be necessary to ensure that the temperature of the imported cuttings was raised uniformly to 15°C after cold storage and prior to fumigation. The practicality of the technique as a commercial treatment will depend on whether it is possible to achieve this without causing unacceptable phytotoxicity.

SUMMARY The American serpentine leaf miner, Liriomyza trifolii (Burgess), was first seen in England in 1977, at a nursery where chrysanthemums were being grown from cuttings imported from Kenya and Malta. Eradicatory action was taken at this and 14 other nurseries where infestations were found during that year. In 1978, 12 infestations were found, originating on chrysanthemum cuttings from Kenya and the Canary Islands and on Gerbera from the Netherlands. In 1979, 132 infestations were found; by then the sources also included Denmark and the USA. Following the withdrawal of the licence permitting imports of chrysanthemum cuttings from Kenya, 63 infestations were found in 1980 and 48 in 1981. Eradication measures rarely required the destruction of infested crops hut frequently required the selective destruction of infested imported plants, together with the application of various insecticidal treatments. To kill adults, fogs and smokes were used; to kill larvae, foliar sprays were applied and persistent systemic insecticides were incorporated in the planting beds; to kill pupae, soil drenches and sterilants were necessary. By the adoption of this control programme and the vigilance of the plant health authorities, eradication of L. trifolii has been, achieved wherever it has been found in England and Wales.

SUMMARY In May 1979 an outbreak of Liriomyza trifolii (Burgess) was detected on glasshouse chrysanthemums, at Efford Experimental Horticulture Station in Hampshire, England. The pest spread to glasshouse tomatoes and then to cultivated and wild hosts outside. An intensive eradication campaign included pest and weed control, monitoring adults with yellow sticky traps, and extensive surveys of potential host plants to determine the spread of the pest. Eleven new hosts of the pest were recorded. In November 1980, following a series of surveys, the pest was deemed not to have survived in the area.