Introduction and Distribution:
This psyllid was first described in Ethiopia, but has been reported in Portugal, Saudi Arabia, and several other African countries including Cameroon, Kenya, Madagascar, Malawi, Reunion, Rwanda, South Africa, Tanzania and Zimbabwe among others. In 2002 it was reported on Tenerife Island in the Canary Islands.
The host range is mainly restricted to members of the Rutaceae family. It has been found on: Clausena anisata, Vespris undulata, Citrus, lemons (C. limon) and limes (C. aurantiifolia). Lemons appear to be their preferred host.
Potential Economic Impact and Description of Damage:
The African citrus psyllid and the Asian citrus psyllid, Diaphorina citri, are both vectors of citrus huanglongbing (HLB or citrus greening). Currently, three species of the bacterium causing HLB have been identified: Candidatus Liberibacter asiaticus, Ca. L. africanus, and Ca. L. americanus. Only the Asian species have been detected in the U.S. The Asian citrus psyllid first arrived in Florida in 1998, and HLB was detected in 2005. A significant latency period occurs for the appearance of symptoms, and it is likely that HLB was present prior to the first find of symptoms. Vector transmission is the primary method of dispersal for any of the HLB species, but the bacterium may also be transmitted through grafting. Asian citrus psyllid has also been reported in Texas (2001), but the African citrus psyllid has not been reported in the continental U.S. If introduced, the African psyllid has the potential to introduce the African form of HLB, and also transmit the Asian form. Among the common symptoms of African citrus psyllid infestation, leaves are severely distorted and appear stunted and galled. Infested leaves often show local chlorosis where nymphs develop on the underside of leaves. In contrast, Asian citrus psyllids form colonies on new plant growth. Once the nymphs mature and leave that site the leaf recuperates its normal color but not its shape. It is common to see the leaves underneath dusted with fecal pellets. The development of pits on the leaves where nymphs have fed occurs only for African, but not Asian citrus psyllids. Although direct feeding damage does occur on the host tree, the ability of the psyllids to vector HLB is when trees are severely diseased general tree decline and leaf drop occurs. Fruit produced by diseased trees is unmarketable because it fails to ripen, from there comes the name “greening”. HLB is highly destructive, and has not been effectively managed to-date in areas where it has been introduced. For more information on HLB symptoms, visit: http://wiki.bugwood.org/Liberibacter_asiaticus.
African citrus psyllid is very susceptible to extreme temperatures. Under hot dry weather, eggs and first instar nymphs are very vulnerable to desiccation. This pest prefers cool moist areas with an altitude over 500-600 meters. Under those conditions citrus growth flushes tend to be more prolonged. Eggs are lemon yellow when just laid and as they mature they turn orange, they are cylindrical with a sharp point. Eggs are commonly laid on the outer margins and shoot tips on the underside of the youngest growth, and sometimes on soft young thorns. Under high populations, females may also lay eggs towards the midrib and the upper side of the leaf. Nymphs vary in color, but in general are pale yellow with bight red eyes. On their fifth instar two pale brown spots appear on the abdomen. They are pretty much sedentary; they get settled on the underside of young leaves and after few days of feeding cup-shaped open galls are formed. Nymphs develop within the open galls and only the dorsal surface of the body is visible. Nymphs only move if disturbed or when under high psyllid densities. Adults are winged; at emergence are pale green with black eyes but then they turn brown as they mature. Wings always remain clear. Males are smaller than females and their abdomen tip is blunt where as the female’s abdomen tip is sharp. Males measure about 2.17 mm where as females measure 2.24 mm. When feeding, adults stand with the abdomen raised at an angle of about 35o to the feeding surface.
Did you knew that an adult African citrus psyllid is able to acquire HLB and transmit the pathogen within 24 hours of initial feeding? In contrast, the Asian citrus psyllid doesn’t transmit the disease until approximately 24 days after initial feeding.
Sex ratios have been observed to fluctuate in the field, but females always predominate. Usually the pre-oviposition period is of 3 to 7 days but in the absence of young foliage it can be much longer. Under those conditions, longevity is also prolonged. Mating may occur two to four times per day and eggs can be laid right away. Eggs have a sharp point that apparently is driven through the epidermis of the leaf and helps maintain good humidity for the egg. In the absence of males, females may maintain fertile for about 11 to 16 days. Each female lays in average 827 eggs but may lay up to 2000 eggs throughout their life. Their life spam is between 17 and 50 days, but there are reports that under experimental conditions these psyllids may live up to 73 days for males and 82 days for females. It takes between 5 and 17 days for eggs to hatch, there are five nymphal stages and it takes between 17 and 45 days to reach adulthood depending on the temperature. After emergence, the first instar nymphs search for a suitable site to feed and settle. They prefer to feed on the youngest growth available, which includes young leaves and soft stems.
Reporting Suspect Samples:
African citrus psyllid is a pest of concern not known to occur in the U.S. Any suspicious specimens should be submitted to your local diagnostic lab (http://www.npdn.org/), or items of concern should be reported to your state department of agriculture (SDA) at: http://nationalplantboard.org/member/index.html. Note that the USDA-APHIS-PPQ and your local SDA may need to implement a quarantine or eradication program if this pest is detected in low population levels. Proper identification is necessary in order to confirm the presence of African citrus psyllid.
Reporting African citrus psyllid in Florida
“If you suspect you have African citrus psyllid infestation, you should contact your local University of Florida County Extension Office (http://directory.ifas.ufl.edu/Dir/searchdir?pageID=3&pl=05), or call the Florida Department of Agriculture & Consumer Services' Division of Plant Industry help line at 1-888-397-1517 or at http://www.doacs.state.fl.us/.”
There are some insecticides that have shown to be effective controlling this psyllid. In Africa, it is recommended that chemical control should be applied as soon as eggs of the psyllid are seen. The use of biological control agents is always preferred. In Reunion-Africa the introduction of the parasite Tamarixia dryi (Waterston) has shown to effectively control this pest. This parasite lays eggs singly under third, fourth or fifth instar nymphs and immatures suck out the body contents. Another important parasitoid that has shown to be effective is Psyllaephagus pulvinatus (Waterston).
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