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Citrus trees diseased #283668 - Ask Extension

Knowledgebase

Citrus trees diseased #283668

Asked October 09, 2015, 5:06 PM EDT

My citrus trees are very sick. They have something unusual according to plant experts at buchanans. They suggested contacting you for help. Five infected trees previously very productive. They said it was a disease that usually infects roses.

Harris County Texas

Expert Response

It would have been great to get some descriptions of what the primary problem is with your trees. However, I do see what looked like black molds in the photos you sent and signs of the Asian citrus psyllid and possibly other sucking insects. Infestations of sucking insects often result in accumulation of honeydew exudates on the tree foliage which becomes substrate for the mold fungus to feed on. Therefore the first critical step to take will be to control the insects so as to eliminate the honeydew accumulation and indirectly the mold fungus.
Since you are likely to have inmatures of these insects as well as adults, your best bet will be to treat with a systemic insecticide as a contact pesticide would not be very effective against the nymphs. The active ingredient of choice will be imidacloprid and the brand name Bayer Advanced should do (I am assuming this is a backyard tree). Please remember to follow the label for correct application of the product and use as per the manufacturers' recommendations.
Olufemi Alabi Replied October 12, 2015, 8:49 AM EDT
Just shared the photos with a colleague, Dr. Setamou, who is an entomologist. Besides, the above diagnosis, your tree might also be suffering from severe attacks of mites, in particular the citrus bud mite (Aceria sheldoni). The mite attack the growing bud of leaves or flowers and this results in the deformation of these organs. You may locate these mites if you open up the “bushy symptom”. In addition to treatment with imidacloprid as recommended above, treat your tress also with any miticide or neem oil which could be found in a nearby gardening center.
Thanks!
Olufemi Alabi Replied October 12, 2015, 11:07 AM EDT

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