Assessment of phosphine fumigation as a plant quarantine measure against Spodoptera littoralis |
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Authors: | C. HAWKES |
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Affiliation: | Rentokil Ltd, Felcourt, East Grinstead, Sussex |
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Abstract: | In laboratory tests first instar larvae of Spodoptera littoralis were killed by phosphine fumigations of 24 and 48 h at a concentration x time product (CTP) of 36 mg h/1. Eggs aged 1–2 days were, however, tolerant to phosphine at a CTP of 144 mg h/1 and this CTP caused severe damage to chrysanthemum cuttings (cv. Freedom). When eggs aged < 1 day and 1–2 days old were preconditioned at 20 oC for 72 h before phosphine fumigation, complete mortality occurred at CTPs at and above 36 mg h/1. Preconditioning for 48 h at 20 oC and for 48 and 72 h at 15 oC did not produce 100% mortality at a CTP of 288 mg h/1. It was suggested that eggs of S. littoralis pass through a phase of tolerance to phosphine which at 20 oC lasts about 4 days after oviposition. There was no indication that phosphine was toxic to chrysanthemum cuttings (cv. Pollyanne) at concentrations of 0–75 mg/1 (CTPs of 18 and 36 mg h/1). Storage at 15 oC was not damaging to cuttings but at 20 oC some damage became apparent. |
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