I have an infestation of aphids on my citrus and pomegranate trees. The bugs are being "farmed" by ants. I read they might actually be bringing the aphids to the trees.
Is this at all a problem? Can my trees still produce good fruit while they're infested?
If not, how can the problem be controlled? What safe insecticides suitable for fruit trees can be used?
I had a similar problem on a newly-planted apple tree. It wasn't fruiting, but the aphid infestation was severely stunting new growth. Although aphids don't infest fruiting plant parts, aphid attacks will weaken the plant as a whole, so a severe infestation will most likely lessen fruit production in some way.
The most affective, 'organic' mode of control for the aphids and the ants (at least for me) was to use a combination of ladybugs (larvae or adult) to attack the aphids in combination with a sticky barrier (like fruit tree grease or a glue band) around the trunk of the tree to stop the ants.
By the way, I found that the glue band works far better than the gloopy gel-type barriers that are available. Glue bands are a product specially made for wrapping around fruit trees to keep climbing pests off. They're a strip of plastic(?) with a very sticky adhesive on one side. You wrap this around the tree, adhesive side out, and tie it on with twine to keep critters from sneaking under it. Here's what it looks like:
If your tree is not too large, you could also spray the aphids with safe insecticidal soap or even just a strong jet of water to knock them off.
I used a Pyrethrum-based spray with success. Pyrethrum is a natural and effective insecticide made from the Chrysanthemum flower. Its lethal dosage for insects is so low that its toxicity is negligible for mammals.
Here are some links with more information:
I found that using Johnson's baby shampoo and water worked well. I used a 64oz spray bottle, about one tablespoon of shampoo and the rest water. It kills the ants and the aphids; I washed it off a few hours later, but found it really didn't make difference -- the next day I found no more ants or aphids anywhere.
I also had a problem with garden snails: I made a regular cup of coffee and diluted it with water, then sprayed the trunk and leaves and now I have great big leaves that are dark green and no more pests. I found the coffee and shampoo also works on many other plants.
