CITRUS CANKER
 


-Citrus canker, caused by a bacterial pathogen Xanthomonas axonopodis pv. citri, is a serious disease of most citrus varieties. The disease causes necrotic lesions on leaves, stems, and fruit.

-Severe infestation can cause defoliation, premature fruit drop, twig dieback, general tree decline, and very bad blemishes on fruit. Trees infected with citrus canker become weak, unproductive, and unprofitable.

-Leaf Symptoms: Lesions appear within 5-7 days under optimal conditions. The early symptoms on leaves appear as slightly raised tiny blister-like lesions. As the lesions age, they turn tan to brown and a water-soaked margin appears surrounded by a yellow ring or halo. The center of the lesion becomes raised and corky. The lesions are usually visible on both sides of the leaf.

-Stem and Twig Lesions: Stem lesions often indicate that the infection has been present for a long period of time. Stem lesions serve as a reservoir for persistent inoculum. Symptoms on twigs and fruit are similar and consisted of dark brown or black raised corky lesions surrounded by an oily or water-soaked margin. As the lesions mature, they appear scabby or corky.

-Fruit Lesions. Lesions are dark brown to black and raised, often surrounded by yellow halos. Symptoms may differ with the citrus cultivar. Lesions cause blemishes and early fruit drop, thereby reducing fruit yield. Citrus canker is highly contagious and can be spread rapidly by wind-driven rain, storm events such as tornadoes and tropical storms, flooding, equipment, and human movement within groves.

CITRUS GREENING

-Citrus greening disease is caused by phloem-limited bacteria in the genus Candidatus Liberibacter. Three species are described, including Candidatus Liberibacter asiaticus, Candidatus Liberibacter africanus, and Candidatus Liberibacter americanus.

-Citrus greening pathogens are transmitted by insect vectors in the family Psyllidae. They also can be transmitted by grafting, by dodder, and possibly by seed. Even though the pathogens are bacteria, the disease does not spread by casual contamination of personnel and tools or by wind and rain.

-The disease often can be recognized in the field by foliar and fruit symptoms.

-Early symptoms of citrus greening disease are small yellow leaves on one limb or section of the tree canopy. The most diagnostic symptoms of citrus greening are leaf mottling that often ignores the leaf veins. The newest leaves may show symptoms resembling zinc deficiency, while older leaves have the characteristic greening mottle. Other symptoms are yellow shoots, twig die-back, poor flowering, and stunting.

-Fruit is small, poorly colored, and/or lopsided. Fruit taste is bitter, medicinal, and sour. Seeds usually abort, and fruit set is poor. Symptoms vary according to cultivar, tree maturity, time of infection, stage of disease, and other abiotic or biotic agents that affect the tree. Chronically infected trees are sparsely foliated and display extensive twig or limb dieback.

DISAPPEARANCE OF HONEY BEES
(COLONY COLLAPSE DISORDER)



-Colony Collapse Disorder is a poorly understood phenomenon in which worker bees from a beehive or Western honey bee colony abruptly disappear.

-The cause or causes of the syndrome are not yet well understood. Proposed causes include environmental change-related stresses, malnutrition, pathogens, mites,  and pesticides.

-A colony which has collapsed from CCD is generally characterized by all of these conditions occurring simultaneously:

--Complete absence of adult bees in colonies, with little or no build-up of dead  bees in or around the colonies.

--Presence of capped brood in colonies. Bees normally will not abandon a hive until the capped brood have all hatched.

--Presence of food stores, both honey and bee pollen:

*  which are not immediately robbed by other bees

*  which when attacked by hive pests such as wax moth and small hive beetle, the attack is noticeably delayed.

 -Precursor symptoms that may arise before the final colony collapse are:

      --Insufficient workforce to maintain the brood that is present

     --Workforce seems to be made up of young adult bees

     --The Queen is present 

     --The colony members are reluctant to consume provided feed, such as  sugar
        syrup and protein supplement.