Silwet L-77 Improves the Efficacy of Horticultral Oils for Control of Boisduval Scale <I>Diaspis boisduvalii</I> (Hemiptera: Diaspididae) and the Flat Mite <I>Tenuipalpus pacificus</I> (Arachnida: Acari: Tenuipalpidae) on Orchids


  • Robert A. Cating
  • Marjorie A. Hoy
  • Aaron J. Palmateer


Pest management of insects and mites on orchids has been based on the use of synthetic organic pesticides. However, less-toxic chemical control is needed by hobbyists and small growers. Orchids from 8 genera were treated with Silwet L-77 alone and no evidence of phytotoxicity was seen. Subsequently, 3 petroleum oils in combination with Silwet L-77 were tested to determine efficacy in suppressing Boisduval scale Diaspis boisduvalii Signoret (Hemiptera: Diaspididae) and the flat mite Tenuipalpus pacificus Baker (Arachnida: Acari: Tenuipalpidae). The results indicate Silwet L-77 increased toxicity of the oils and increased removal of the scales and mites from foliage over oil alone, yet no phytotoxicity was observed in any of the plants treated. Petroleum oil + Silwet L-77 is considered low-toxic, may be less expensive than some pesticides, and may conserve natural enemies, making it a potential addition to an integrated pest management program for orchids.

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