Effects of Kaolin Clay Application on Flower Bud Development, Fruit Quality and Yield, and Flower Thrips [Frankliniella spp. (Thysanoptera: Thripidae)] Populations of Blueberry Plants

Kaolin-based emulsions have multiple modes of action that can offer broader protection to blueberry crops from flower thrips and other blueberry pests (Glenn et al., 1999; Knight et al., 2000; Lapointe, 2000;

Puterka et al., 2000; Unruh et al., 2000). Kaolin clay particles adhere to plant surfaces with the aid of wetting agents. These particles form a physical barrier over the flowers, leaves, stems, and fruit. If these particles attach to the waxy cuticles of pest insects they interfere with feeding, as well as cause irritation and desiccation (Glenn et al., 1999; Swamiappan et al., 1976). Also, kaolin has no nutritional value to herbivorous insects and can potentially reduce the digestibility of plant tissue (Howe and Westley, 1988). Induced plant resistance to pest insects is also possible, as plants sprayed with kaolin can become unrecognizable as suitable hosts (Bar-Joseph and Frenkel, 1983; Glenn et al., 1999). Host suitability to flower thrips can diminish with intensification of reflected UV-light (350 to 390 nm) visible to flower thrips (Glenn et al., 1999; 2002; Lewis, 1997; Parker et al., 1995).