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Psyllids or jumping plant lice are small plant-feeding insects that tend to be very host specific, i.e. they only feed on one plant species (monophagous) or feed on a few related plants (oligophagous). Together with aphids, phylloxerans, scale insects and whiteflies they form the group called Sternorrhyncha, which is considered to be the most "primitive" group within the true bugs (Hemiptera). They have traditionally been considered a single family, Psyllidae, but recent classifications divide the group into a total of seven families; the present restricted definition still includes more than 70 genera in the Psyllidae.

Psyllid fossils have been found from the early Permian before the flowering plants evolved. The explosive diversification of the flowering plants in the Cretaceous was paralleled by a massive diversification of associated insects, and many of the morphological and metabolic characters that the flowering plants exhibit may have evolved as defenses against herbivorous insects.

Several genera of psyllids, especially among the Australian fauna, secrete coverings called "lerps" over their bodies, presumably to conceal them from predators and parasites.^1]

Coevolution

Insect-plant interactions have been important in defining models of coevolution and cospeciation, referring to whether plant speciation drives insect speciation and vice versa, though most herbivorous insects probably evolved long after the plants they feed on.

Status as pests

Citrus greening, known as "Huanglongbing" is associated with the presence of a bacterium Liberibacter asiaticum is an example of a plant pathogen that has coevolved with its insect vector, the "Asian Citrus Psyllid", ACP, Diaphorina citri, such that the pathogen causes littl e or no harm to the insect, but causes a major disease which can reduce citrus quality, flavor, and production as well as causing citrus trees to die. The ACP was found in Florida in 1998, and has since spread across the southern U.S. into Texas. This disease, also known as Huanglongbing, was found in Florida citrus groves in 2005. Management methods to reduce the spread of this disease and psyllid populations depend on an Integrated Pest Management approach using insecticides, parasitoids, predators, and pathogens specific to the AsCP. Due to the spread of Citrus Greening world wide and the growing importance of psyllid spread diseases an "International Psyllid Genome Consortium" was established.^[2] Insect genomics provides important information on the genetic basis of the pests biology which may be altered to suppress psyllid populations in an environmentally friendly manner. The emerging psyllid genome continues to elucidate psyllid biology, expanding what is known about gene families, genetic variation, and gene expression in insects. Thus far two new psyllid viruses have been discovered, and are being examined as potential biological control agents to reduce psyllid populations. Psyllid cell cultures have also been established by several researchers working with virus propagation, and as a system to propagate the Can. Liberibacter bacterium for molecular studies on infection and replication. Studies on the microbiota have also identified four new species of bacteria. Thus far ten microbial organisms have been identified within these psyllids, among them the primary endosymbiont, whose genome has been sequenced and posted at the NCBI database, as well as a Wolbachia species.

Some of the agriculturally-important pest species are now classified in the family Triozidae.

Psyllid fossils have been found from the early Permian before the flowering plants evolved. The explosive diversification of the flowering plants in the Cretaceous was paralleled by a massive diversification of associated insects, and many of the morphological and metabolic characters that the flowering plants exhibit may have evolved as defenses against herbivorous insects.

Several genera of psyllids, especially among the Australian fauna, secrete coverings called "lerps" over their bodies, presumably to conceal them from predators and parasites.^1]

Coevolution

Insect-plant interactions have been important in defining models of coevolution and cospeciation, referring to whether plant speciation drives insect speciation and vice versa, though most herbivorous insects probably evolved long after the plants they feed on.

Status as pests

Citrus greening, known as "Huanglongbing" is associated with the presence of a bacterium Liberibacter asiaticum is an example of a plant pathogen that has coevolved with its insect vector, the "Asian Citrus Psyllid", ACP, Diaphorina citri, such that the pathogen causes little or no harm to the insect, but causes a major disease which can reduce citrus quality, flavor, and production as well as causing citrus trees to die. The ACP was found in Florida in 1998, and has since spread acros s the southern U.S. into Texas. This disease, also known as Huanglongbing, was found in Florida citrus groves in 2005. Management methods to reduce the spread of this disease and psyllid populations depend on an Integrated Pest Management approach using insecticides, parasitoids, predators, and pathogens specific to the AsCP. Due to the spread of Citrus Greening world wide and the growing importance of psyllid spread diseases an "International Psyllid Genome Consortium" was established.^[2] Insect genomics provides important information on the genetic basis of the pests biology which may be altered to suppress psyllid populations in an environmentally friendly manner. The emerging psyllid genome continues to elucidate psyllid biology, expanding what is known about gene families, genetic variation, and gene expression in insects. Thus far two new psyllid viruses have been discovered, and are being examined as potential biological control agents to reduce psyllid populations. Psyllid cell cultures have also been established by several researchers working with virus propagation, and as a system to propagate the Can. Liberibacter bacterium for molecular studies on infection and replication. Studies on the microbiota have also identified four new species of bacteria. Thus far ten microbial organisms have been identified within these psyllids, among them the primary endosymbiont, whose genome has been sequenced and posted at the NCBI database, as well as a Wolbachia species.

Some of the agriculturally-important pest species are now classified in the family Triozidae.

References

1. ^ Oppong, C.K., Addo-Bediako, A., Potgieter, M.J. & Wessels, D.C.J. 2010. Nymphal behaviour and lerp construction in the mopane psyllid Retroacizzia mopani (Hemiptera: Psyllidae). African Invertebrates 51 (1): 201-205.[1]
2. ^ International Psyllid Genome Consortium

• Oppong, C.K., Addo-Bediako, A., Potgieter, M.J. & Wessels, D.C.J. 2009. Distribution of the eggs of the mopane psyllid Retroacizzia mopani (Hemiptera: Psyllidae) on the mopane tree. African Invertebrates 50 (1): 185-190.[2]
• Burckhardt, D. & Kotrba, M. 2009. A review of Afrotropical plant-lice of the genus Moraniella, with description of a new species (Hemiptera: Psylloidea: Psyllidae: Rhinocolinae). African Invertebrates 50 (2): 287-294. [3]
• Marutani-Hert, M., Hunter, W.B., Hall, D.G. 2009. Establishment of "Asian citrus psyllid" (Diaphorina citri) cell cultures. In Vitro Cellular & Developmental Biology.Animal, 45(7): 317-320.
• Marutani-Hert, M., Hunter, W.B., Katsar, C.S., Sinisterra, X.H., Hall, D.G., Powell, C.A. 2009. "Reovirus"-like sequences isolated from adult "Asian citrus psyllid", (Hemiptera: Psyllidae: Diaphorina citri). Florida Entomologist, 92(2): 314-320.
• Hunter,WB, Dowd, SE, Katsar, CS, Shatters, Jr, RG, McKenzie, CL, Hall, DG. 2009. Psyllid biology: expressed genes in adult "Asian citrus psyllid", Diaphorina citri Kuwayama. The Open Entomology Journal 3: 18-29.
• Boykin, LM, Bagnall, RA, Frohlich, DR, Hall, DG, Hunter, WB, Katsar, CS, McKenzie, CL, Rosell, RC, Shatters, Jr, RG. 2007. Twelve polymorphic microsatellite loci from the "Asian citrus psyllid", Diaphorina citri Kuwayama, the vector for citrus greening disease, "Huanglongbing". Molecular Ecology Notes: online (doi: 10.111/j1471-8286.2007.01831.x).
• Avery, P.B., Hunter, W.B, Hall, D.G., Jackson, M.A., Powell, C.A. and M. E. Rogers 2009. Diaphorina citri (Hemiptera: Psyllidae) infection and dissemination of the entomopathogenic fungus Isaria fumosorosea (Hypocreales: Cordycipitaceae) under laboratory conditions. Florida Entomologist 92: 608-618.

External links

On the University of Florida / Institute of Food and Agricultural Sciences Featured Creatures website

• Blastopsylla occidentalis, eucalyptus psyllid
• Boreioglycaspis melaleucae
• Diaphorina citri, Asian citrus psyllid
• Glycaspis brimblecombei, red gum lerp psyllid
• Pachypsylla venusta, hackberry petiole gall psyllid

The Family Psyllidae is a member of the Superfamily Psylloidea. Here is the complete "parentage" of Psyllidae:

• Domain: Eukaryota Whittaker & Margulis,1978 - eukaryotes
  • Kingdom: Animalia C. Linnaeus, 1758 - animals
    • Subkingdom: Bilateria (Hatschek, 1888) Cavalier-Smith, 1983 - bilaterians
      • Branch: Protostomia Grobben, 1908 - protostomes
        • Infrakingdom: Ecdysozoa A.M.A. Aguinaldo et al., 1997 ex T. Cavalier-Smith, 1998 - ecdysozoans
          • Superphylum: Panarthropoda Cuvier
            • Phylum: Arthropoda Latreille, 1829 - Arthropods
              • Subphylum: Mandibulata Snodgrass, 1938
                • Infraphylum: Atelocerata Heymons, 1901
                  • Superclass: Panhexapoda
                    • Class: Insecta C. Linnaeus, 1758 - Insects
                      • Subclass: Dicondylia
                        • Infraclass: Pterygota - Winged Insects
                          • Superorder: Condylognatha
                            • Order: Hemiptera C. Linnaeus, 1758 - True Bugs, Cicadas, Hoppers, Aphids and Allies
                              • Suborder: Sternorrhyncha - Plant Lice
                                • Infraorder: Psyllomorpha
                                  • Superfamily: Psylloidea
                                    • Family: Psyllidae - Jumping Plant Lice