Citrus Greening


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Citrus Greening

  1. 1. ABSTRACT • Huanglongbing (citrus greening) is a bacterial disease that is threatening the citrus industry worldwide. An insect known as the Asian citrus psyllid, Diaphorina citri, carries the organism that causes citrus greening, Candidatus Liberibacter asiaticus. Candidatus Liberibacter spp. are phloem-limited plant pathogenic bacteria.The phloem system of the plant transports sugars, which are the food source of the plant, bidirectionally through the plant. The phloem system of the plants transports the sugars from sources of photosynthetic activity (leaves) in the plant to flowers, fruits, roots, seeds. • Psyllids are the main means of transmission to plants. An infected psyllid feeds on a healthy tree and injects the bacterium into the phloem . Candidatus Liberibacter asiaticus enters in sieve tube and uses sugar which are transported by phloem thus changes the shape of phloem cell. It also created gap between phloem cell. In our modeling we have calculated the fractal dimension of normal phloem cell and the fractal dimension of same cell after HLB and we have found that as the disease increases fractal dimension of the cell is decreasing. It decreases from 1.9209 to 1.8541.
  2. 2. Huanglongbing (HLB, formerly known as citrus greening) is one of the most destructive diseases of citrus, debilitating the productive capacity of citrus trees . The HLB disease is caused by a fastidious α proteobacterium, Candidatus Liberibacter spp. The bacterium is phloem limited, transmitted by psyllid vectors, and has not been cultured yet .
  3. 3. Asian Citrus Psyllid The Asian citrus psyllid is a small insect that feeds on the leaves and stems of citrus trees. Once a tree is infected with HLB,there are some cures but the psyllid could have made a loss in economy before you see the symptoms.It’s better to prevent it. The best way to prevent the disease from killing citrus trees is to stop the Asian citrus psyllid by some preventive measures. It is of three types:- 1. Ca. L. asiaticus 2. Ca. L. africanus 3. Ca. L. americanus
  4. 4. Scientific Information About Asian Citrus Psyllid Scientific Classification Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Hemiptera Suborder: Sternorrhyncha Superfamily: Psylloidea Family: Psyllidae Genus: Diaphorina Species: D. citri Binomial name Diaphorina citri
  5. 5. PSYLLIDS Psyllids are the main means of transmission to plants. An infected psyllid feeds on a healthy tree and injects the bacterium into the phloem. Once a tree is infected with the bacterium, there is no known cure for the disease. This in part is because the bacterium is inside the vascular system of the plant (systemic) and is therefore very difficult to access.
  6. 6. Life Cycle Of Psyllid Psyllid’s are small insects about 3 to 4 mm in length with a simple life cycle that processes from egg through 5 nymphal instars to adult stage. Psyllid females lay their bright yellow-orange eggs on tip of shoots.Number of eggs laid depends on the host plant as well as temperature. Example : 1. Mean of 857 eggs were deposited on grapefruit,whereas a mean of 527 eggs were deposited on rough lemon. 2. At 25 C eggs hatch in 2 to 4 days whereas 7 to 9 days at 20 C .
  7. 7. It has an egg stage, 5 wingless intermediate stages called nymphs, and winged adults Adult The pest insect Egg 5 Nymphs (insects molt to grow bigger) 9
  8. 8. The eggs are yellow-orange, tucked into the tips of tiny new leaves, and they are difficult to see because they are so small The pest insect 10
  9. 9. Modes of Transport For Psyllid The Asian citrus psyllid can fly short distances and be carried by the wind. However, a main way the Asian citrus psyllid spreads throughout the state is by people transporting infested plants or plant material. For this reason, everyone in California is asked to not move citrus and to only purchase citrus trees from reputable, licensed nurseries in your area.
  10. 10. How does the psyllid get around? The psyllid can spread naturally by flying or it can hitch a ride on plants into new areas of California Photos courtesy of the CDFA Psyllid-infested curry leaves shipped in boxes from Hawaii Unprocessed fruit from Mexico The pest insect On ornamentals in floral bouquets from Mexico Citrus riding across the border in passenger or cargo vans 12
  11. 11. Candidatus Liberibacter spp. are phloemlimited plant pathogenic bacteria.The phloem system of the plant transports sugars, which are the food source of the plant,bidirectionally through the plant. The phloem system of the plants transports the sugars from sources of photosynthetic activity (leaves) in the plant to flowers, fruits, roots, seeds.
  12. 12. Working Of Psyllid The asian citrus psyllid is a phloem limited bacteria which when attacks a tree creates space between compactly arranged phloem cells.After that it starts taking food from the phloem cell and does not allow the minerals to reach the leaves which ultimately results in dying and turning back of leaf.
  13. 13. The peptidoglycane layer of the Gram negative cell wall can be visualized (PG) in between the inner membrane cytoplasmic membrane (CM) and the outer cell wall membrance (OM).
  14. 14. . Electron micrograph of Ca. Liberibacter cells in a sieve tube of sweet orange leaf in Saudi Arabia
  15. 15. Its Effects • Causes worldwide crop loss. • Reduced profitability for citrus growers. • Mature trees, when infected, decline and become non - productive. • Young infected trees may never bear fruit.
  16. 16. Symptoms Primary leaf symptoms include :     Yellowing of leaves along veins Asymmetrical blotchy mottle. Newly formed leaves become small and upright Shows a variety of chlorotic patterns that resemble various Nutrient deficiency symptoms such as zinc and manganese As infection progresses, characteristic symptoms are : • Lopsided fruit • Color inversion and • Aborted seeds Symptoms do not always occur together on the same tree. Trees may be infected for long periods of time without showing distinct symptoms. Lack of specificity in disease symptoms, unknown latent period of the disease in field trees, and our poor understanding of the effect of environment conditions on symptom development point to the need for field-based diagnostic tests for early detection.
  17. 17. An early sign of the disease is uneven (asymmetrical) yellowing of the leaves Leaves with HLB disease have a blotchy mottled yellow pattern that is not the same on both sides of the leaf. The bacterial disease HLB Leaves with nutrient deficiencies (Zinc is an example) have the same yellow pattern on both sides of the leaf. Zinc 19
  18. 18. Symptoms may not show up in the tree until 1-2 years after it becomes infected The bacterial disease Figure 25. Blotchy chlorosis throughout leaf
  19. 19. Within 3-5 years after infection, the tree stops bearing fruit and eventually dies. The bacterial disease This citrus tree in a backyard in Florida is obviously very sick, with few leaves and no fruit. 21
  20. 20. Countries Affected The disease is widespread in :1. Asian countries 2. South California. 3. Africa 4. Brazil 5. Florida 6. South and Central America 7. Mexico 9. Georgia 8. Louisiana
  21. 21. Where did Asian citrus psyllid and the HLB disease come from? Most likely ACP and HLB came from India or Asia. Both the psyllid and disease are affecting citrus production in Brazil, Cuba and Florida. California has the psyllid in 2 counties in southern California but does not yet have the disease. HLB Disease found in Florida in 2005 and Cuba in 2007 Distribution of the pest and disease Figure 34. Map courtesy of UFL IFAS Extension Map out of date per Brian Both the psyllid and the HLB disease Asian citrus psyllid, but not the disease 23
  24. 24. CONCLUSION
  25. 25. How can I help prevent the pest and disease from establishing? •Buy only certified disease-free trees from a reputable nursery Detection and Reporting •Don’t bring plant material from other states or countries •Learn to recognize the pest and disease symptoms •Check flush foliage of citrus and citrus relatives wherever you go •Call your County Agricultural Commissioners office or the CDFA hotline immediately, if you suspect you have either the pest or the disease
  26. 26. Some Other Ways To Control Citrus Greening • Using temperature-controlled growth chambers, we evaluated the time duration and temperature required to suppress or eliminate one type of psyllid i.e. ‘Ca. L. asiaticus’ • Spraying trees weekly with horticulture grade oils. • Use of soap citrus save-r. • Use of highly toxic pyrethoid. Eg. cyfluthrin (Tempo) • Imidacloprid (Merit) a systemic neonicotinoid • Use of RSVP plant scrub.
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