Details

Autor(en) / Beteiligte

• Chapman, M.H. (California, Univ., Berkeley (USA). Dept. of Entomological Sciences)
• Hoy, M.A

Titel

Relative toxicity of Bacillus thuringiensis var. tenebrionis to the two-spotted spider mite (Tetranychus urticae Koch) and its predator Metaseiulus occidentalis (Nesbitt) (Acari, Tetranychidae and Phytoseiidae)

Ist Teil von

• Journal of applied entomology (1986), 1991-01, Vol.111 (1-5), p.147-154

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

1991

Link zum Volltext

Beschreibungen/Notizen

• Bacillus thuringiensis var. tenebrionis (Btte) wettable powders were tested in the laboratory to determine their relative toxicity to the two-spotted spider mite (Tetranychus urticae Koch) and its predator Metaseiulus (Typhlodromus) occidentalis (Nesbitt). These microbial preparations, when tested at 0.1X, 0.5X, and 1.0X the recommended field rate of 0.9 kg ai/75.7 l/acre (2.0 lb ai/20.0 gal/acre) caused little mortality to adult females of T. urticae but were considerably more toxic to M. occidentalis females at 48 h. Female T. urticae exhibited 90.0 plus minus 14.2 per cent survival vs. 26.0 plus minus 23.4 per cent survival for M. occidentalis at the field rate. Starvation of female predators for 24 h prior to treatment with Btte wettable powder significantly increased mortality. Neiter predator nor spider mite eggs treated with Btte wettable powder at the field rate suffered a depression in hatch rate (98.0 per cent and 97.2 per cent hatch, respectively, of eggs treated when 24 h old). However, only 65.0 per cent of the resulting immature predators reached adulthood compared to 88.8 per cent of the immature spider mites. Female predators which survived treatment as eggs and developed on residues did not show a significant decrease in fecundity. Thus, under these laboratory conditions, Btte was moderately toxic to predator mites. Finally, treatment of M. occidentalis females with other Btte products (Mycogen M-ONE(R) and Sandoz Trident(R) and with Bacillus thuringiensis var. kurstaki (Dipel 2X) also resulted in significant mortality