Scale Insects & Bromeliads
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Scale Insects Information for Bromeliad Plants
Scale insects are the superfamily Coccoidea of the insect order Homoptera. About 5,000 species of them have been described. The scale insects are minute to small, highly specialized, and generally spend their entire life near the spot where they hatched. All of their forms that possess legs have one-segmented or two–segmented tarsi, bearing a single claw. Females are always wingless, but males may be winged (with one pair of wings) or wingless. Adult males have no functional mouthparts. First instars (crawlers) have functional legs and are very mobile, but later instars may be legless and sedentary. Immature stages and adult females feed on plant juices by inserting their long stylet mouthparts into a host plant and sucking out the juices.
Worldwide there are 21 families of scale insects. Margarodidae and Ortheziidae are considered “most primitive” because the females have abdominal spiracles and the males often have faceted eyes. The other families are considered “most advanced” because the adult females never have abdominal spiracles and the adult males have simple eyes. The 3 largest families are Diaspididae (armored scales), Pseudococcidae (mealybugs), and Coccidae (softscales).Generally scale insects are considered pests destructive to agricultural crops. However, some species can furnish useful products well known in commerce, such as shellac (from Laccifer lacca), cochineal red dye from (Dactylopius coccus), crimson lake, and other dyes. Some species produce wax of marketable value, such as Chinese wax which is used for candles. Jewelry is fashioned from some of the hard shelled margarodids. Dactylopius spp. have been used as biological control agents for Opuntia cacti in Australia, Ceylon, India, Hawaii, and Mauritius. More than half of the successful biological control projects in the world have been against scale insects. Even with these impressive figures scale insects are still horrendous pests of agriculture. It has been estimated that if they were left uncontrolled by natural means and chemicals their potential damage could reach several billions of dollars in the U.S. alone.
Scale insects attack all parts of plants from roots to buds, flowers, and fruits. Some are subterranean in habit. Some produce honeydew in great quantities, whereas others, such as Diaspididae (armored scales) do not produce the excretion. Some species cause galls to form on their hosts, others cause leaf rolling, surface pitting or other tissue changes. Other species cause disease-like symptoms by injecting irritating salivary products into the host plant. The dispersal of coccids on a plant or plants nearby is by the active first instar or crawler stage. Over longer distances some crawlers may be spread by wind, but generally the movement of infested plant material in commerce has been responsible for dispersal over long distances. Scale is commonly found on Bromeliads and other tropical plants.
Hamon, A.B. 1998. Introduction to Scale Insects.
The Asterolecaniidae, or pit scales, are an unusual group in which many members can cause “pits” to occur on their host plants. Many resemble the soft scales in appearance, being colored light tan to brown to green in color, slightly convex to convex in lateral profile, and being 2-6 mm long. Many are considered as damaging pests on their hosts.
Common Species on Bromeliads
- Asterolecanium bambusicola Boisduval. This is one of the more common pit scales found on various bamboo species. The coloration of this scale is light green to light brown with a cream colored to orange margin. The approximate size of this pit scale is 2-4 mm long.
- Asterolecanium epidendri Bouché (orchid pit scale). This pit scale is very common on orchids and occasionally found on bromeliads. They tend to be brown to yellowish-tan in color. The orchid pit scale is approximately 1-3 mm long.
Unlike armored scales, soft scales are not covered by non-living waxy armor. Instead, they are generally covered by a thin layer of wax which is excreted by various pores located on the insect body. There is much morphological variation within the family. In many cases the bodies of the females are convex in profile but some species have a flat lateral profile.
Reproduction can vary depending upon species. Some require males whereas other species reproduce through parthenogenesis (asexual reproduction). General life cycle for an individual is from egg-crawler-second instar-third instar-adult. Females are often times sedentary and become affixed to a feeding location.
Common Species on Bromeliads
- Coccus hesperidum Linnaeus (Brown soft scale). The brown soft scale is a polyphagous pest species that is common to many ornamental plantings within Florida. The general appearance of this scale is a small (2-5 mm long) light brown “disc” located on the leaves or stems of its hosts. The body shape is generally oval and may range from flat to slightly convex in profile.
Ensign scales are some of the more ornate scale insects that people encounter. The females are generally covered with white waxy plates and often times carrying white ensign-like ovisacs (cottony masses containing eggs) attached to their bodies.
Common Species on Bromeliads
- Orthezia Tillandsiae Morrison. This orthezid is generally found on the leaves of bromeliads in the genus Tillandsia. They are easy to spot and appear as small, grayish white, mobile tubes. The economic importance is unknown but it appears that most Tillandsia can support small populations without too much of an effect on the host plant.
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