Silwet L-77 Improves the Efficacy of Horticultral Oils for Control of Boisduval Scale Diaspis Boisduvalii (Hemiptera: Diaspididae) and the Flat Mite Tenuipalpus Pacificus (Arachnida: Acari: Tenuipalpidae) on Orchids (Report‪)‬

The Orchidaceae is believed to be the largest family of flowering plants (Bechtel et al. 1992; Dressler 1993; Tsavkelova et al. 2008) with approximately 19,000 named species (Atwood 1986; Dressler 1993). Orchids are the second most economically important flowering plant produced in the United States and sales continue to grow (Jerardo 2006). As orchid popularity continues to grow, so will the desire for pest and disease information, as illustrated in the question and answer section of Orchids magazine published by the American Orchid Society, which frequently contains questions submitted by hobbyists and commercial growers concerning the identification and control of orchid pests and diseases. Common arthropod pests of orchids that can be difficult to control include the Boisduval scale Diaspis boisduvalii Signoret (Hemiptera: Diaspididae) and several species of mites. Boisduval scale is one the most important orchid pests and can be difficult to control with traditional chemical methods because females possess a hard covering (Hamon 2002; Johnson 2009). Boisduval scale is commonly introduced into an orchid collection on an infected plant and scales can move quickly to a variety of orchids (Johnson 2009). Mites also can be a major problem on cultivated orchids (Johnson 2008). Mite species that are known pests of orchids include the two-spotted spider mite (Tetranychus urticae Koch, Arachnida: Acari: Tetranychidae) and several flat mites (Tenuipalpidae) such as the orchid mite (Tenuipalpus orchidarum Parfitt), the phalaenopsis mite (Tenuipalpus pacificus Baker), and the oncidium mite (Brevipalpus oncidii Baker) (Johnson 2008).