|Crop Knowledge Master|
Hemiberlesia lataniae (Signoret)
Victoria L. Tenbrick, Research Associate
Arnold H. Hara, Entomologist
Beaumont Research Center
The Latania scale has a very wide host range. Hosts include, avocado, azalea, bamboo, banana, bird of paradise, bougainvillea, breadfruit, carambola, carob, cattleya orchids, coconut and other palms, croton, cycads, guava, hala, lychee, mango, oleander, philodendron, plumeria, rose, sapodilla, soursop, and sugarcane (Zimmerman, 1948; Dekle, 1965). Latania scale infests over 300 hosts in Florida (Dekle, 1965).
Latania scale occurs in all tropical regions of the world. An immigrant to the Hawaiian Islands, it was first found here in 1898 (Zimmerman 1948).
The first sign of latania scale is the presence of armor on upper and lower leaf surfaces, fruits, and stems of plants. The female armor is round and convex, white or dirty white, and 1.5 to 2 mm (less than 1/8 in) in diameter. When the population is large, the shape of the armor becomes irregular. The cast skins of the nymph form a large, yellowish to dark brown spot forming a central or subcentral (off center) exuvium (Zimmerman, 1948; Dekle, 1965). Male armor is smaller and oval rather than round. The armor must be pried off to reveal the insect attached to the plant by thread-like mouthparts that start at the middle of the body and are as long or longer than the body. The adult female insect is flat, pear-shaped, lemon yellow, without wings, legs, or eyes (Dekle 1965, Witherell 1984). Dead scales are dark brown and dried rather than plump. Armored scales feed on plant juices and cause a loss of vigor, deformation of infested plant parts, yellowish spots on leaves, loss of leaves, and even death of the plant (Dekle, 1965; Beardsley and Gonzalez, 1975). Since scales are spread by introduction of infested material they are a quarantine problem on exported potted plants, cut flowers, and cut foliage.
The number of days for each developmental stage and the number of generations per year depend on temperature, humidity, and rainfall (Beardsley and Gonzalez 1975). Based on a generalized life history of other tropical species, 30 days is the approximate time to complete the life cycle from egg to reproducing adult.
Eggs are laid under the armor of the female where they develop and hatch.
The first stage after hatching is the only nymphal stage with legs, so the insects are called crawlers. Crawlers may stay under the maternal armor for several hours until outside conditions, especially temperature and humidity, are favorable. After they leave cover, they wander for a period ranging from minutes to days, but they usually wander for a few hours. At the end of the wandering period, they flatten against the leaf or stem and begin to secrete their armor (Beardsley and Gonzalez, 1975).
Newly settled nymphs insert their piercing-sucking mouthparts into plant tissue and start feeding on plant juices. Female nymphs shed their skin twice as they grow and develop. Males have 5 stages of development (crawler, nymph, prepupa, pupa, and adult) and do not feed or enlarge their armor during the last three stages (Beardsley and Gonzalez, 1975). The cast skins, called exuviae, are incorporated into the armor and form a dot. The armor is non-living and is made of cast skins, threads, and liquid produced by the insect (Beardsley and Gonzalez, 1975).
Female latania scales appear larvae-like. They remain under armor in one place throughout their lives to feed and reproduce. Males are very different in appearance and behavior from females. The males are tiny, winged creatures with eyes and legs. Mature males emerge from the armor in the late afternoon. They do not feed, and they live for only a few hours to mate. Mate-finding is probably aided by pheromones secreted by females (Beardsley and Gonzalez, 1975). Because of the late emergence and short life of males, it is rare to find them in the field. Latania scale has both bisexual and parthenogenetic races (Beardsley and Gonzalez, 1975). Parthenogenic races can reproduce without males, because parthenogenic races reproduce asexually.
Since female armored scales are not capable of wandering once they have settled and started feeding, long range dispersal happens by passive transport of infested plant material. Short range dispersal happens when crawlers search out places to settle and feed (Beardsley and Gonzalez, 1975). It is the crawler stage that can be carried directly from place to place by people, animals, birds, ants, and wind currents (Dekle, 1965; Beardsley and Gonzales, 1975). Wind is an agent of dispersal and also one of mortality, since crawlers dislodged by wind may not land on suitable host plants. Adult males are capable of only weak flight or wind transport. Living only a few hours, they do not feed. The two developmental stages of males prior to the adult stage, prepupa and pupa, also do not feed. Female adults and feeding nymphs feed by inserting mouthparts into plant tissue and sucking plant juices.
Insect names often come from the plants they are associated with. Latania, the specific name as well as part of the common name of this scale, is after a genus of fan palms. However, Latania is often confused with the woody shrub Lantana because of the name similarity (Zimmerman, 1948).
Since armored scales are spread chiefly through movement of nursery stock, only propagative material that is free of scales should be planted. Adequate plant spacing is important, because armored scales seldom spread from plant to plant unless the crowns of the plants are in contact with each other (Beardsley and Gonzalez, 1975). As plants grow, pruning maintains spacing and allows maximum coverage when using insecticides.
Ladybird beetles, or ladybugs, have been introduced to control armored scales in Hawaii. Some of these, such as Telsimia nitida Chapin, (Coleoptera: Coccinellidae) have become established on the major Islands. These beetle adults and larvae are carnivorous; they eat soft-bodied insects. Scale covers that look chewed and have no insect underneath are signs that predators have been feeding on the scales.
Parasitic wasps will lay eggs in developing scales. The developing wasp larvae hatch and become parasites that digest the contents of the scale body. When the wasp is fully developed, the wasp emerges from under the scale armor. Parasitic wasps can be very effective in controlling armored scales (Dekle, 1965). In Hawaii, the wasp Aphytis chrysomphali (Mercet) (Hymenoptera: Aphelinidae) parasitizes latania scales (Zimmerman, 1948).
Scraping and scrubbing to remove scales from plants is an effective mechanical control tactic. Removing scales is especially important on exported plant materials, since intact armor is a sign of scale infestation; plants with armor may not pass quarantine inspection.
Insecticide mode of action and formulation are important because the armor covers and protects all stages but the crawler and the adult male. Contact insecticides target the crawler stage; systemics target adult females and nymphs as well as male nymphs. Since scales have natural enemies, care must be taken to conserve these natural enemies. Populations of other pests, such as white flies and other scales, may rise if their natural enemies are affected by chemical control. Spraying should be determined by presence of scales in the field rather than by the calendar. Scales are best detected by regularly inspecting all areas of the fields for scales. When detected, directing spray at hotspots rather than uninfested areas helps to conserve natural enemies and also helps to delay pesticide resistance.
In the packing house, insecticidal soaps can be used in the cleaning water to kill crawlers while scrubbing off adults. Dipping without scrubbing in a soap-pyrethroid solution for five minutes is only 70% effective against adults and nymphs (Hansen et. al., 1992). Even though scales are killed, it takes several days for the body to dry so removal of the armor is required to assure inspectors that the plant material is insect free.
Beardsley, J. W. Jr. and R. H. Gonzalez. 1975. The biology and ecology of armored scales. Annual Review of Entomology. 20: 47-73.
Dekle, G. W. 1965. Arthropods of Florida Vol. 3, Florida Armored Scale Insects. Division of Plant Industry, Florida Department of Agriculture, Gainesville. 265 pp.
Hansen, J. D., A. H. Hara and V. L. Tenbrink. 1992. Insecticidal dips for disinfesting commercial tropical cut flowers and foliage. Tropical Pest Management 38: 245-249.
Witherell, P. C. 1984. Methyl bromide fumigation as a quarantine treatment for latania scale, Hemiberlesia lataniae (Homoptera: Diaspididae). Florida Entomologist 67 (2) 254-262.
Zimmerman, E. C. 1948. Insects of Hawaii Vol. 5 Homoptera: Sternorhyncha. University of Hawaii Press, Honolulu. 464 pp.