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.
Laboratory investigations were made into the effect of cultivar type, prior cold storage, fumigation temperature and methyl bromide concentration, on the efficacy of a fumigation treatment to control Liriomyza trifolii in chrysanthemum cuttings. The tests related to the standard quarantine treatment used in the UK to control Spodoptera littoralis on imported chrysanthemum cuttings : cold storage for 2 days at 1 -2°C followed by methyl bromide fumigation at 15°C with a concentration time product (CTP) of 54 g h/m3. L. trifolii larvae, within detached leaves, and 1 -2 and 2 -3 day old pupae, were treated. Methyl bromide concentrations of 6.75 or 13.5 g/m3 were used to achieve a range of CTPs and thus obtain accurate dose-response lines and estimates of the LD99 and LD99.9 for each insect stage. Fumigation temperatures were 8, 11 or 15°C.Efficacy of the standard treatments differed between the three cultivars tested, but the LD99 for larvae remained below 54g h/m3. Decreasing fumigation temperature to 11°C or less increased LD99 values for larvae and pupae and substantially increased variability. There is therefore little scope for using fumigation temperatures of less than 15°C for quarantine purposes. Omitting the cold storage treatment prior to fumigation did not significantly affect efficacy of fumigation. Reducing the methyl bromide concentration from 13.5 to 6.75 g/m3 did not significantly affect the LD99 for larvae but significantly reduced LD99s for pupae.
Individual cuttings and leaves of chrysanthemum infested with eggs and larvae of the alien leaf miner Liriomyza trifolii (Burgess) and batches of pupae, were treated in the laboratory in order to find an effective quarantine treatment to control the pest in imported cuttings. Cold treatment for 2 days at 1–2°C followed by methyl bromide fumigation at 15°C with a range of concentration time products (CTPs) was used to obtain accurate dose‐response lines and estimate the LD99 and LD99.9 for each stage of the insect. The largest estimates of the LD99 for eggs, larvae and pupae up to 3 days old were less than the CTP specified in the existing (as at September 1983) United Kingdom statutory fumigation treatment designed to prevent the entry of Spodoptera littoralis (Boisd.). This statutory schedule for unrooted cuttings consists of cold storage for 2 days at 1–2°C and then fumigation with methyl bromide at a CTP of not less than 54 g·h/m3 with a minimum treatment period of 4 h at a minimum air temperature of 15°C. Our results indicate that the Spodoptera treatment should give high levels of kill for most stages of L. trifolii provided a CTP of 54 g·h/m3 and a temperature of 15°C (throughout the fumigation) arc achieved uniformly within packs of cuttings when they are fumigated in their transit boxes in commercial practice. The practicality of the technique will depend on whether it is possible to achieve this without causing unacceptable phytotoxicity. 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 prc‐packing inspections in exporting countries would still need to be maintained, to minimize any risk of importing pupae. The results are presented in full by Mortimer E.A. & Powell, D.F. (1984). Development of a combined cold storage and methyl bromide fumigation treatment to control the American serpentine leaf miner Liriomyza trifolii (Diptera: Agromyzidae) in imported chrysanthemum cuttings. Annals of Applied Biology105, (3), 443–454.
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