Abdominal gland secretion ofBledius rove beetles as an effective defence against predators |
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Authors: | Johannes L M Steidle and Konrad Dettner |
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Institution: | (1) Ecogen Inc., 2005 Cabot Blvd. West, 19 047 Langhorne, PA, USA;(2) Present address: Dept. of Biology, Geneva College, 3200 College Ave., 15 010 Beaver Falls, PA, USA |
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Abstract: | Recent investigations indicated thatBacillus thuringiensis delta-endotoxins (DET) possess aphidicidal activity in an artificial diet bioassay. Crystalline preparations of CryIIA, CryIIIA
and CryIVD solubilized in a slightly alkaline sucrose/amino acid diet clearly imparted toxicity toward adults of potato aphid,Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) after 4–5 days of continuous feeding. No obvious feeding deterrence was noted in these assays,
as copious honeydew was produced and aphids often died in a feeding position. CryIIIA which was solubilized in aphid diet,
but filtered to remove spores or crystalline toxin lacked aphidicidal activity. Spores from an acrystalliferous strain (EG2205)
were not toxic by themselves at 7.75×105 spores/ml aphid diet, but did restore toxicity to the filtered CryIIIA solution. Therefore, low levels of spores may be very
effective in concert with DET for aphicidal activity. Results also clearly demonstrated that a suspension of crystalline CryIIIA
alone, without spores, exhibited toxicity. Therefore, DET may be more toxic to the aphids when imbibed as a fine suspension,
perhaps indicating the need for slow solubilization into the aphid midgut. |
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Keywords: | Bacillus thuringiensis insecticidal crystal protein Homoptera Aphididae Macrosiphum euphorbiae |
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