Aphids often produce a substance known as honeydew that supports the growth of unsightly black sooty mold. Aphid predators recognize the presence of this sugary material as a sign of aphids (i.e. their lunch) nearby. Gardeners have found that spraying sugar water solutions on plants attracts lady beetles and other predators that can help keep the aphid population in check. Now researchers in various parts of the country have confirmed this technique in a number of field trials and have also found it effective in attracting certain species of tiny parasitic wasps.
To put this strategy to work in your garden, mix a solution of one pound of sugar in one gallon of water and spray it on some leaves in an area where aphids are starting to appear. Mixtures of three parts water to one part lemon-lime soda or one part yeast plus one part sugar to ten parts water have also been suggested for attracting the good guys to a garden. You can also find commercial mixes that attract beneficials under the names "Wheast," "Bugchow," or "BugPro."