Answer: Aphids will attack nearly every plant with tender foliage and a good defense would be to hose the pests off with a strong stream of water. This disorients some and kills others without upsetting the balance of nature. Ladybugs typically arrive to feast on aphids when populations are large, so using pesticides to kill the aphids can also kill the beneficial predators such as ladybugs.
As for determining what a plant is prone to (insects or diseases), I'm afraid you'll need to do a search on each specific plant. You'll find a huge array of information if you do a plant search on Google or Yahoo. Unfortunately, there is no list of plants not susceptible to aphids.
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