Diaphorina citri
Diaphorina citri
The Asian citrus psyllid (Diaphorina citri Kuwayama, 1908) is an insect belonging to the Liviidae family.
Systematics –
From a systematic point of view it belongs to:
Eukaryota Domain,
Kingdom Animalia,
Sub-kingdom Eumetazoa,
Bilateria branch,
Phylum Arthropoda,
Subphylum Hexapoda,
Insecta class,
Subclass Pterygota,
Exopterygota cohort,
Subcoorte Neoptera,
Paraneoptera superorder,
Rhynchotoidea section,
Order Rhynchota,
Suborder Homoptera,
Sternorrhyncha section,
Psylloidea superfamily,
Liviidae family,
Subfamily Euphyllurinae,
Genus Diaphorina,
D. citri species.
The terms are synonymous:
– Dysphoria citri Kuwayama, 1908;
– Euphalerus citri (Kuwayama, 1908).
Geographic Distribution and Habitat –
The Asian citrus psyllid is an insect native to Asia but which later spread to other parts of the world; it is present in the Middle East, South and Central America, Mexico and the Caribbean and has recently also arrived in the Mediterranean basin.
In the United States, psyllis was first detected in Florida in 1998 from where it spread to various federated states and control and quarantine rules have been adopted in these areas.
Morphology –
Adult Diaphorina citri is an insect about four millimeters long with a tawny and mottled brown body and a light brown head.
The body is covered with a whitish, waxy secretion that makes it look dusty. The front wings are wider in the back and have a dark border around the periphery with a pale space near the apex.
The antennae are light brown with black tips.
It is recognized because it generally adopts an upside-down and tail-up posture while sucking in the lymph.
The nymph of this insect has five moults and is yellow-orange in color and has no abdominal spots. Wing pads are prominent, especially in later stages.
The eggs are recognized because they are about 0.3 millimeters long, almond-shaped, thicker at the base and tapering towards the top. They are pale in color at first but turn yellow and later orange before they hatch. The long axis is positioned vertically to the surface of the leaf.
Attitude and Life Cycle –
The biological cycle of Diaphorina citri begins with the deposition of the eggs; the deposition takes place on the tips of the growing shoots, at the opening point of the leaves.
A female can typically lay up to 800 eggs during her lifetime, which can last for several months.
The entire development cycle of this insect lasts from two to seven weeks depending on the temperature and the time of year.
The nymphs of this insect live on new shoots of citrus trees. As they feed, sucking up the sap, they produce a toxin that causes the tips of plants to die or writhe, preventing the leaves from expanding normally. However, this insect’s direct feed damage is considered less than its role as a vector of Huanglongbing (HLB), also called citrus greening, which is a deadly bacterial disease for citrus trees. Already present in almost all producing regions, HLB is now threatening the Mediterranean basin with the arrival of psylla.
Ecological Role –
Diaphorina citri is a sap-sucking hemiptera insect of the citrus family.
It is one of the two confirmed vectors of citrus greening disease and an increasingly wider distribution range in citrus growing areas.
The feeding of this insect can be a vector of bacteria that cause one of the most devastating diseases of citrus fruits, precisely the disease of greening of citrus fruits. Affected trees produce small, asymmetrical, partially green and unsaleable fruit due to their poor size and quality. In addition, there is laboratory evidence indicating that it can also transmit another serious citrus disease caused by the Citrus tristeza virus (CTV) which is a virus belonging to the genus Closterovirus, which causes the disease called citrus sadness.
Diaphorina citri has a number of natural enemies including hoverflies, various ladybird species, a number of parasitic wasp species and other insects. One of these wasps, Tamarixia radiata, has been shown to be very effective in controlling the parasite and has been successfully released and established in numerous citrus growing areas, such as Florida.
The Brachygastra wasp is also an ide parasite of D. citri and the role of ladybirds can play an important role in containing the insect.
Although psyllium adults and nymphs can be controlled through the use of a wide range of insecticides, it is emphasized that citrus greening disease can best be controlled through an integrated strategy that involves the use of plant material. healthy, vector control and prompt removal of infected trees and branches.
Furthermore, the use of insecticides heavily alters the useful entomofauna, the relationship of biocenoses, and other ecological systems such as birdlife and so on.
Research has also recently focused on understanding the various sensory signals that Diaphorina citri uses to locate its host plant. Understanding the insect’s behavior can lead to better methods for its control. One study showed that the perception of reflected ultraviolet wavelengths increased the attraction to a yellow trap. Attempts to demonstrate psyllid’s attraction to volatile (airborne) odors have failed to produce an effective attractant. It seems that this tiny insect is attracted to color (yellow wavelength and UV) and decides to stay and feed on a particular plant only after it has settled on a leaf and tasted it by probing with its mouthparts. Small molecules such as formic acid and acetic acid stimulate probing activity. These substances can be used in new and innovative traps or other devices.
Further research found that the spatial distribution of eggs and nymphs is a result of the movement patterns of pregnant females in response to egg-laying sites. Dispersion indices were used to confirm the aggregate or contagious distribution pattern of the D. citri population within the tree and could be expressed by the negative binomial distribution. Measurable tests showed that egg and nymph distributions in naturally occurring psyllidae populations were highly aggregated, following initially aggregated migrations of adults and contagious dispersal of adults within trees with increasing population density.
It has also been seen that the increase in population density in the controlled fields has led to a greater dispersion of the population and has been the consequence of the dispersion of females and their selection of spawning sites. Since the exponential increase in dispersion can be predicted by means of the population density of immature stages, a sampling plan was developed from the relationship between dispersal behavior and population density rather than from the relationship between economic damage and population density. .
Beyond the evolution of statistical distribution techniques and insect dynamics, it is clear that the containment of this insect must take into account agronomic and, above all, agroecological practices with a decrease in crop specializations, increases specific and intraspecific biodiversity (using , in this regard, during the planting phase, a greater number of indigenous varieties) and also making use of associations, etc.
The further use of insecticides or other health devices can lead to a further worsening of the ecological status of entire areas with a dangerous collapse of the already delicate natural balance.
In this sense, it is necessary to make use of technicians specialized in biological control and competent in the field of agroeocology.
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Pollini A., 2002. Manual of applied entomology. Edagricole, Bologna.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.
Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/5441533/original.jpg