The following is information on products from the neem tree that are used for insect and disease control.
Neem pesticides are derived from seeds of the neem tree (Azadirachta indica syn. Melia azedarachta a relative of the mahogany tree), a subtropical shade tree growing or cultivated in many developing nations. Many different forms are available commercially and knowing what's out there can really help. Seed extracts (oils) are common and may contain certain insecticidal ingredients. Soaps or just the general seed oil are also available.
Neem pesticides containing azadirachtin (AZA) kill insects by disrupting their growth and development. They are also strong insect repellents. Neem products with AZA control a broad range of pests, providing superior control of chewing insect pests such as caterpillars, leaf beetles, and sawflies. The amount of AZA present in a formulation varies and may reflect whether the product is a Ready-to-Use (RTU) formulation or a concentrate. Commercial applicators can buy AZA containing brands such as Azatin, Azatrol, Azamax, etc. Home Garden trade names include Safer BioNeem, Neem-Away Insect Spray, and others.
Clarified hydrophobic extracts of neem oil are products that do not contain any AZA and are similar in use pattern to insecticidal horticultural oils and powdery mildew fungicides. Trade names include Green Light Neem Concentrate, Trilogy, and many others. This is the type most often found on retail store shelves.
Fatty acids from neem seed are insecticidal soap (potassium salt fatty acid)/neem blends that vary in their concentration of AZA and should be used with the same care as any insecticidal soap. Trade names include Bon-Neem and Organica K+ Neem.
Many neem products carry OMRI listings that also allow them to be useful tools in organic production. Formulations (particularly those with AZA) provide a level of pest management equal to that of many synthetic counterparts from a botanical source.
Information from Casey Sclar, IPM Coordinator, Longwood Gardens