African citrus psyllid

Scientific name

Trioza erytreae (Hemiptera: Triozidae)

Similar species

Asian citrus psyllid, Diaphorina citri

• The African and Asian citrus psyllid can be distinguished using wing characteristics.
• Adult Asian citrus psyllids have front wings that are widest near the tip and can have either transparent wings with white spots or light brown wings with a central beige band.
• Adult African citrus psyllids have front wings pointed at the tip. All four wings are clear and unspotted.
• In juveniles, wing padswing pads:
  undeveloped or incomplete wing structures that are found on the immature individuals of insects that do not undergo complete metamorphosis, e.g., stink bugs, leaf-footed bugs, grasshoppers
  of the African citrus psyllid are smaller than the Asian citrus psyllid.

Immature psyllids are sometimes confused with aphids and whitefly pupae.

• Psyllids and aphids can be easily distinguished by examining the rear of the abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  . Adult aphids have two dark tubular structures called siphunculisiphunculi:
  paired, triangular-shaped tubes projecting from the rear of an aphid abdomen; also referred to as cornicles
  . The African citrus psyllid does not have siphunculisiphunculi:
  paired, triangular-shaped tubes projecting from the rear of an aphid abdomen; also referred to as cornicles
  on the rear of its abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  during any developmental stage.
• Adult psyllids are also differentiated from aphids by behavior. Psyllids are very active and able to jump whereas aphids move slowly when disturbed.
• Whitefly pupae have fringe-like projections encompassing the body with eyes and antennae not readily viewable from a top-down view compared to immature psyllids.
• Psyllid nymphs have eyes and antennae that are easily seen and smaller, more conspicuous fringe-like projections surrounding certain areas of the body.

Distribution

United States: Not known to occur.

Worldwide: Africa, Madeira, Saudi Arabia, Portugal, and Yemen.

Native to Africa.

Diagnostic characteristics

Adults

• 1.9 - 2.5 mm (0.07 - 0.10 in.) in length; 0.5 mm (0.02 in.) in width.
• Pale green upon emergenceemergence:
  used to describe the completion pupation that culminates in the appearance of the adult form of an insect
  , but the headhead:
  one of the three main body segments in insects; the anterior-most segment containing the many sensory structures including the eyes, antennae, and mouthparts
  , top of the abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  (dorsum), antennae, feet (tarsi), and leg segments immediately above the feet (tibiae) turn from brown to black as the insect matures.
• Hind legs are stouter than front legs.
• Females have a pointed tip (ovipositor) on the posteriorposterior:
  orientation pertaining to the rear of the body
  end of the abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  .
• Males have a blunt tip on the posteriorposterior:
  orientation pertaining to the rear of the body
  end of their abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  .
• Four, clear unspotted wings. The two forewings are pointed at the tip and are approximately 3 mm (0.12 in.) in length.
• At rest, the wings are held tent-like above the body.
• The abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  is inclined at least 35° from the headhead:
  one of the three main body segments in insects; the anterior-most segment containing the many sensory structures including the eyes, antennae, and mouthparts
  at the surface of the host planthost plant:
  the plant the provides sustenance for an insect
  during feeding.

Immatures

• Five nymphal instars.
• 0.3 - 1.7 mm (0.01 - 0.07 in.) in length.
• Pale yellow but yellowish-orange, olive green, or dark grey are also possible.
• Red eyespotseyespots:
  markings on an insect, usually the wing, that resemble a large eye
  .
• Flattened (dorso-ventrally compressed).

Eggs

• 0.28 mm (0.01 in.) in length and 0.13 mm (0.005 in.) in width.
• Pale yellow to orange.
• Cylindrical.
• Deposited on new flushflush:
  period of rapid growth in the terminal shoots of citrus trees that may be associated with flowering or may be vegetative
  (actively growing foliage).

Hosts

Citrus hosts

• common mandarins (including tangerine), Citrus reticulata
• grapefruit, Citrus paradisi
• lemon, Citrus limon
• Mexican (or Key) lime, Citrus aurantifolia
• pummelo, Citrus maxima
• sour orange, Citrus aurantium
• sweet orange, Citrus sinensis
• trifoliate orange, Citrus trifoliata

Non-citrus hosts

• curry leaf, Murraya koenigii
• kumquat, Fortunella japonica
• limeberry, Triphasia trifolia
• mock orange, Philadelphus spp.
• orange boxwood, Severinia buxifolia
• orange jasmine or orange jessamine, Murraya paniculata

Host damage

Fruits

• African citrus psyllid is a vector of citrus greening disease, a disease that causes misshapen, bitter fruit and ultimately kills the tree (see Comments section).
• Honeydew honeydew:
  the sugar-rich waste product excreted by aphids, mealybugs, and scales insects as a result of feeding on the phloem of plants
  excreted by psyllids coats the outside of fruits and leaves and promotes the growth of sooty mold fungus that inhibits photosynthesis, weakens the plant, and makes fruit unattractive.

Leaves

• Yellowed or chlorotic.
• Sometimes stunted and galled on new plant growth.

Biology

The African citrus psyllid is extremely temperature sensitive and will not develop at temperatures exceeding 25 °C (77 °F). Their lifespan is 17 - 50 days, and females are capable of laying up to 2000 eggs during their lifetime. Nine to ten generations may occur per year. Eggs are laid on the leaf margins of young citrus foliage. The nymphs emerge from small cup-like pit galls to congregate, feed, and mature on the underside of the leaves. The African citrus psyllid prefers cool and humid conditions, whereas the Asian citrus psyllid prefers lower elevations and warmer areas.

Comments

The African citrus psyllid is an extremely efficient vector of citrus greening (Candidatus Liberibacter asiaticus), a highly virulent and fatal bacterial disease that inhabits the food transport tissue (phloem-limited) of citrus trees. Common symptoms of citrus greening are mottling and yellowing (chlorosis) of the leaves that can resemble some nutrient deficiencies, especially zinc deficiency. Trees are frequently stunted and have partial defoliation. Twig dieback, leaf and fruit drop, and off-season blooming are other common symptoms. The fruit is affected as well, appearing misshapen, improperly colored, and with a bitter taste.

All phloem-feeding, honeydew-producing insect pests have the potential to be tended by ants. The ants feed on the honeydewhoneydew:
the sugar-rich waste product excreted by aphids, mealybugs, and scales insects as a result of feeding on the phloem of plants
excreted by the pest and protect the pest from natural enemies. This protection can disrupt biological control programs.

References

Carter, K. 2009. A brief review of the Asian citrus psyllid (ACP). Cooperative Extension, University of California-Riverside. (http://groups.ucanr.org/CLUH/files/72671.pdf).

(EPPO/ CABI) European and Mediterranean Plant Protection Organization/Centre for Agricultural Bioscience International. 1979. EPPO data sheet on quarantine organisms, No. 46, Trioza erytreae. (http://www.eppo.org/QUARANTINE/insects/Trioza_erytreae/TRIZER_ds.pdf).

Espinosa, A., and A. C. Hodges. 2009. NPDN Master Gardener Bugwood Wiki fact sheet. (http://wiki.bugwood.org/Trioza_erytreae).

Gottwald, T. R., J. V. da Graça, and R. B. Bassanezi. 2007. Citrus Huanglongbing: The pathogen and its impact. Plant Health Progress. (http://www.plantmanagementnetwork.org/sub/php/review/2007/Huanglongbing/Huanglongbing.pdf).

Halbert, S. E., and K. L. Manjunath. 2004. Asian citrus psyllids (Sternorrhyncha: Psyllidae) and greening disease of citrus: A literature review and assessment of risk in Florida. Flor. Entomol. 87: 330-353. (http://www.fcla.edu/FlaEnt/fe87p330.pdf).

Mead, F.W. 1976. The South African citrus psyllid, Trioza erytreae (Del Guercio) (Homoptera: Psyllidae). Entomol. Circ. 168. Fla. Dept. Agric. Consumer Serv., Div. of Plant Industry. (http://www.doacs.state.fl.us/pi/enpp/ento/entcirc/ent168.pdf).

Samways, M. J. 1987. Prediction of upsurges in populations of the insect vector (Trioza erytreae: Hemiptera: Triozidae) of citrus greening disease using low-cost trapping. J. Appl. Ecol. 24: 881-891. (http://www.jstor.org/stable/2403987).

Sullivan, M., and R. Zink. 2010. Sampling and survey considerations for citrus greening in the Western states: potential differences for huanglongbing between Florida and the western states. USDA, Center for Plant Health Science and Technolgy, Nationwide Weeds Management Laboratory. (http://www.aphis.usda.gov/plant_health/plant_pest_info/citrus_greening/downloads/pdf_files/hlb.pdf).

Tsai, J. H. 2009. Citrus greening and its psyllid vector: Crop and commodity management. In E. B. Radcliffe,W. D. Hutchison, and R. E. Cancelado [eds.], Radcliffe's IPM World Textbook, University of Minnesota, St. Paul, MN. (http://ipmworld.umn.edu/chapters/TsaiGreening.htm).

(USDA) U.S. Department of Agriculture, Citrus Health Response Program. 2008. Known host plants of huanglongbing (HLB) and Asian citrus psyllid. Fla. Dept. of Agr. and Consumer Serv., Division of Plant Industry. (http://www.doacs.state.fl.us/pi/chrp/greening/hostlist.pdf).

Van Den Berg, M. A., and C. D. Fletcher. 1988. A bibliography of the citrus psylla, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), up to 1987. Phytoparasitica. 16: 47-61.

Van Den Berg, M. A. 1990. The citrus pyslla, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae): A review. Agric. Ecosyst. Environ. 30: 171-194.

Van Den Berg, M. A., V. E. Deacon, and C. D. Thomas. 1991. Ecology of the citrus psylla, Trioza erytreae (Hemiptera: Triozidae), mating, fertility, and ovipositionoviposition:
the act of depositing eggs
. Phytophylactica 23: 195-200.

Authors

Martin, K.W., A.C. Hodges, and N.C. Leppla