Start with the least toxic, and then reduced-risk products. Diazinon, for example, has been a popular treatment for aphids. However, these pests can be controlled with hard sprays from the garden hose. Spray daily until the problem is solved. Ladybugs are natural predators.
Insecticidal soap is effective, as are products with neem.
Fire ants can be especially annoying, and diazinon drenches have been one of several mound treatments used by home gardeners. Organic home remedies for treating ants include drenching a mound with straight vinegar, soapy water or boiling water. Be extremely careful approaching and treating a mound. Baits are effective synthetic treatments, and to many, your best bet. Mealy bugs appear on stems and buds.