Mites on Cultivated Orchids

Paul Johnson
Yellow speckles or browning of leaves on your orchids? Webbing of silk on various plant parts and no spiders to be seen? Consider mites as possible culprits. Mites are tiny creatures related to spiders and ticks, and are not insects. Plant-feeding mites can be thought of as plant parasites and are often amongst the most serious pests of cultivated orchids. Common orchid cultural conditions in homes and hobby greenhouses can favor mites, and the use of pesticides removes natural predators and
more » ... al predators and allows development of resistant populations. Sources and Identification Mite species that are pests on cultivated orchids generally fall into two main categories, spider mites, and flat mites. The latter are also called false spider mites, but the name flat mite is preferred as it is accurately descriptive and avoids confusion with spider mites. There are other pest species of mites, but they are generally of less importance. The most common spider mite recognized as a persistent pest of orchids is the common two-spotted spider mite (Tetranychus urticae), but the carmine spider mite (Tetranychus cinnabarinus) may be an unrecognized pest species in North America. The spider mites are a yellowish-green and usually with two large dark areas on either side of the body at about midlength. They are active species that is easily seen wandering the plants. Spider mites received their name because of the silk webbing that they produce, not because they may appear like small spiders. The two-spotted is also known by other common names, including the "red spider mite" because of an orange-red over-wintering form. However, it is possible that in some cases the red form of the two-spotted may actually be the carmine spider mite. Both species are global, feed on many kinds of plants (polyphagous), and are easily transported on many kinds of plants. Flat mites recognized as pests on orchids are the orchid mite (Tenuipalpus orchidarum), the phalaenopsis mite (Tenuipalpus pacificus) and the oncidium mite (Brevipalpus oncidii). Tenuipalpus orchidofilo was described recently and was reported as a pest of