The survival of three species of Tetranychidae mites: Tetranychus evansi (tomato red spider mite), Tetranychus ludeni (bean spider mite) and Tetranychus urticae (two-spotted mite), exposed to gamma irradiation doses of 200, 300, 400, 500 and 600 Gy was investigated. The aim was to identify an irradiation dose capable of killing or sterilising mites infesting horticultural produce to prevent movement to and colonisation of host plants in non-infested regions or countries. Eggs were irradiated separately; otherwise, to simulate naturally occurring mite populations, mixed life stages (immatures and adults) were combined and the treatment effects compared to nonirradiated controls. Irradiated eggs of all species failed to develop and hatch at 200 Gy and above. Tetranychus urticae was the most tolerant species, requiring an irradiation dose of 300 Gy to ensure all adult females were sterilised. Sterilised adults continued to lay eggs, but these eggs failed to develop or hatch. Tetranychus evansi and T. ludeni were sterilised when irradiated at 200 Gy. Based on these results, a dose of 300 Gy is recommended as a phytosanitary measure to prevent the survival of these species of Tetranychidae pests of horticultural produce in non-infested regions. Combined with data from other studies this study proposes a generic dose for Tetranychidae mites of 375 Gy.

Summary The effect of two lemon by‐product aqueous extracts at different concentrations (14, 7, 3.5 and 1 mg mL−1) was tested against the in vitro growth of Alternaria alternata. Prior to extraction, one batch of by‐product was dehydrated by freeze‐drying (untreated by‐product), while the other batch was treated by microwave irradiation in conjunction with freeze‐drying (microwave‐treated by‐product). High‐performance liquid chromatography (HPLC) was employed for the identification of individual phenolic compounds with potent antifungal activities. Both lemon by‐product aqueous extracts inhibited the mycelial growth and suppressed the spore germination of the fungus in a concentration‐dependent manner. In general, the extracts obtained from the microwave‐treated lemon by‐product displayed enhanced antifungal activity than those obtained from the untreated one. Scanning electron microscopy (SEM) revealed that both lemon by‐product extracts affected the hyphal morphology of the fungus. The antifungal activity of the extracts was attributed to their phenolic acid and ascorbic acid contents.

The survival of four species of thrips (Frankliniella occidentalis, Frankliniella schultzei, Thrips tabaci and Thrips imaginis) exposed to gamma irradiation at doses of 0, 200, 300, 400 and 500 Gray was investigated. The aim of the work was to identify a generic dose of gamma radiation capable of killing or sterilising thrips infesting horticultural produce to prevent movement to, and colonisation of host plants in noninfested regions or countries. To simulate naturally occurring thrips populations, mixed life-stages were irradiated, and the effects compared with a nonirradiated control. The eggs of F. occidentalis and T. tabaci were more tolerant to irradiation than those of F. schultzei and Thrips imaginis, but none of the F. occidentalis or T. tabaci eggs developed beyond first stage larvae when irradiated at a target dose of 200 Gy. In mixed life-stage tests, all species had a similar tolerance to gamma irradiation. At a target dose of 200 Gy, all species were sterilised and no further offspring were produced. Based on these results, a minimum generic dose of 200 Gy would be sufficient to control these species of thrips in fresh horticultural produce destined for export to thrips-sensitive regions. A target dose of 250 Gy will provide a further margin of safety, until large-scale confirmatory trials are completed.

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