Texas Invasive Species InstituteToxoptera citricida
Brown Citrus Aphid
Synonyms: Aphis citricidus, Aphis aeglis
Class: Insecta
Order: Hemiptera
Family: Aphididae
Photographer: Florida Division of Plant Industry Archive
Source: www.invasive.org
Adult Description: Brown citrus aphid species can be differentiated from other aphids infesting citrus based on the brown body color. Adults are about .1 inches in length, soft-bodied, pear-shaped with six segmented antennae and two cornicles (triangle-shaped tubes) at the rear of the abdomen. A darker band occurs where the two longest leg segments meets and there 30 hairs on the cauda (also at rear of abdomen) which is another distinguishing feature for Toxoptera citricida.
Larva Description: Immatures resemble adults but are a reddish-brown color and smaller than adults.
Host Plant: All Citrus varieties.
Ecological Threat: Toxoptera citricida is considered one of the most serious citrus pests. It infests and damages buds and flowers. This insect does not directly damage citrus fruits but does prevent bud growth and distorts leaves creating stunted plant growth. Also, the brown citrus aphis is a successful transmitter of citrus tristeza closterovirus (CTV). This closterovirus causes stem pitting, stunting, low yields and poor fruit quality. Also, this virus spreads by fruit budding from infected budwood, both locally and country to country. In North and South America tens of millions of trees have been destroyed by CTV vectored by Toxoptera citricida. The aphid can acquire the virus after feeding on infected plants for 5-60 minutes; but thankfully it loses the ability to transmit the virus after 24 hours. The closterovirus is able to spread quicker with the presence of the brown citrus aphid than through grafting of CTV infected budwood. Finally, honeydew (sugar-rich waste product) excreted by the aphids’ coats the fruits and leaves and promotes the growth of sooty mold fungus that also inhibits photosynthesis, makes fruit un-marketable and weakens the plant. By physically damaging citrus crops, vectoring a dangerous citrus closterovirus and facilitating the growth of a sooty mold fungus; the brown citrus aphid is a dangerous pest.
For more information on Citrus Tristeza Closterovirus click here
Biology: The adults reproduce both sexually and asexually (parthenogenesis) to produce live young. Toxoptera citricida prefers new growth and feeds exclusively on species of Citrus. Winged forms of the brown citrus aphid typically develop when new growth is no longer available on the tree so they can disperse. Aphids are capable of wide dispersal and can travel up to 20 miles.
History: The pest was first reported in Florida at the end of 1995, where it is now well established. Before the presence of Toxoptera citricida the melon/cotton aphis Aphis gossypii was able to transmit CTV. Unfortunately, the brown citrus aphid is a more efficient vector of CTV because it only feeds on Citrus species. Thankfully, this aphid has not been found in any other citrus producing states.
U.S. Habitat: Throughout subtropical citrus-growing areas.
Distribution
Native Origin: China
U.S. Present: Florida
Resembles/Alternatives
The brown citrus aphid resembles the black citrus aphid (Toxoptera aurantii), but the latter is somewhat smaller than the brown citrus aphid.
Management
Overall there are not and biological control agents known to specifically impact the brown citrus aphid, however, there are natural parasites, predators and pathogens that can affect the aphid present in Florida. Studies to find specific biological controls for Toxoptera citricida are continuing.
Chemical treatment may be beneficial in protecting nursery stock and budwood sources. Overall, treatment is warranted only in young groves (< 3 yrs. old) if over 50% of expanding terminals are infested. Surveys for aphids should be conducted early in flushing cycles. Systemic materials, such as Temik or Admire, applied to the soil will give good control with minimal impact on beneficial species, but the time required for uptake of these materials makes them useful for prevention, but not as a response to aphid infestation.
References
Internet Sources
http://edis.ifas.ufl.edu/ch055
http://edis.ifas.ufl.edu/cg004
http://www.eppo.int/QUARANTINE/virus/Citrus_tristeza/CTV000_ds.pdf
http://cisr.ucr.edu/brown_citrus_aphid.html
http://entnemdept.ufl.edu/creatures/citrus/bc_aphid.htm
http://idtools.org/id/citrus/pests/factsheet.php?name=Brown%20citrus%20aphid
