Not an organic control, but here is the only thing that worked for me:
I had a serious pest problem on citrus, white sapote, and on a large gardenia bush in my yard. These plants were being farmed by ants (bigheaded ants = Pheidole megacephala), an invasive species to Florida and which proved impervious to all the controls I tried on them. These ants would just stroll right through any treated areas and continue farming. They were farming both aphids and scales on the above mentioned types of plants in my yard.
Eventually, completely frustrated, I decided to try treating systemically for the aphids and scales by broadcasting granular Imidacloprid around the bases of the affected plants and watering it in as instructed. That soon killed the ahhids and scales on the plants and the crazy ants finally moved on since their farming efforts were being thwarted on the treated plants. The Imidacloprid treatement tends to last for about two to three months depending on how rainy it is here at the time.
Unfortunately, once the Imidacloprid's effectiveness would begin to wear off, the ants would return and start farmng the plants again requiring another broadcasting of Imdacloprid.
NOTE: Imidacloprid unfortunately is toxic to honeybees and has now been shown to be a cause of honeybee colony collapse. Bees take nectar from flowers of treated plants and return to the hive and feed the nectar to the incubating bee larvæ, preventing them from maturing. The affected honeybees also eventually die from aging out and because now there are no larvæ to replace those old worker bees, the colony begins to fail. To try to minimize or eliminate its impact on honeybees I now schedule applications of Imidacloprid during times when the treated plants have finished blooming for their season.
OK — HTH
Paul M.
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