Sunday, April 26, 2009

Oleander plants?

we have several oleander trees and started to notice that the leaves started turning brown and dying, it would then jump to the other trees and so on and so on. I thought it was some type of disease and trimmed them down ( way down) now some are coming back healthy but others are still brown, does anyone know what this can be and what I can treat them ? any suggestions would be appreciated


thank you

Oleander plants?
Its hard to say what your problem may be without having a little more detailed info, but I will try to give you my professional opinion and you can decide if it applies.





Providing your oleanders have not been subjected to any kind of cultural stress, such as pesticide phytotoxicity, salt burn (salinity) in the soil, severe drought, or freezing temperatures, a possible cause could be what is called "Oleander Leaf Scorch" (Xylella fastidiosa) which is a xylem infecting bacterium that is spread by certain leafhoppers (insects) while feeding, primarily the glassy-winged sharpshooter. The leaf margins or tips of the leaves including the edges appear scorched, turn yellow, then brown, and dry out. These symptoms can appear at anytime of the year but spread rapidly when the weather starts to warmup. The reason some of your plants appear to be more infected than others may be due to the fact that you have two or more different cultivars (varieties) or flower colors planted together. Some cultivars are less succeptible than others. Some plants will only live about 2 yrs once the disease is discovered and others may last for 3-5 yrs. There is no known cure for this disease once it gets established inside the plant! By pruning them heavily, you have temporarily supressed the visual symptoms. The new growth will appear healthy for a while, but will eventually go back to looking diseased and brown. The only thing you can do is to get on a scheduled spray program to control the leafhoppers and stop them from feeding on your plants. Also, the only way to detect this Xylella fastidiosa bacterium is to do an "ELISA" test, which must be done by an agricultural laboratory. Sorry to bring you this negative info, but I'm letting you know what you may be dealing with here. Good luck...


http://cals.arizona.edu/PLP/plpext/disea...


http://www.plantmanagementnetwork.org/pu...


http://ag.arizona.edu/yavapai/anr/hort/b...





...$Billy Ray$
Reply:Thank you! And great question btw. It had my brain working overtime!...Billy Ray Report It

Reply:It sounds like they have freezer burn.





If you are in a hot climate, it could be they need more water:





From:


http://www.oleander.org/culture.html#Anc...





"Care





Water Requirements - Established plantings of oleanders are considered tolerant of ordinary drought conditions, with most plantings on Galveston Island receiving little or no supplement to natural rainfall. However, drought stress does have adverse effects, such as causing a reduction in growth rate and flower production. Supplemental watering at the rate of 1-2 inches per week, during dry weather conditions, promotes continuous flowering and constant growth of plants.





Fertilizer Requirements - As in the above case of water requirements, established plantings of oleanders generally do not require fertilization, but plants may respond favorably when fertilized by increasing growth rate and flower production. Signs of unfavorable soil nutrient levels for oleanders include light green, often small leaves, short internodes, lack of terminal growth of stems and sparse flowering. A general recommendation can be used where two pounds each of actual nitrogen, phosphorous and potassium are applied for 1000 square feet area occupied by roots of the plants. The first application made in early spring followed by a second application made in early fall. Oleanders growing in lawns that are properly fertilized generally will not require supplemental fertilization."


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