Insect Control: Biological and Synthetic Agents - Index of

5 Azadirachtin, a Natural Product in Insect Control
A J Mordue (Luntz), University of Aberdeen,
Aberdeen, UK
E D Morgan, Keele University, Keele, UK
A J Nisbet, University of Melbourne, Werribee,
Australia
ß 2010, 2005 Elsevier B.V. All Rights Reserved
5.1. Introduction 185
5.1.1. The Neem Tree 186
5.2. Azadirachtin Research up to 1985 186
5.3. Chemistry of Neem Products 187
5.3.1. Neem Limonoids 188
5.3.2. Isolation of Azadirachtin 188
5.3.3. Analysis 188
5.3.4. Stability and Persistence 189
5.4. Neem Insecticides in Pest Control 190
5.4.1. Background 190
5.4.2. Use in Integrated Pest Management 191
5.4.3. Toxicity to Nontarget Organisms 191
5.4.4. Resistance 191
5.4.5. Systemic Action 192
5.5. Antifeedant Effects of Azadirachtin 192
5.6. Neuroendocrine Effects of Azadirachtin 193
5.6.1. Insect Growth Regulation 193
5.6.2. Reproduction 194
5.7. Studies on the Mode of Action of Azadirachtin 195
5.7.1. Studies using Insect Cell Lines 195
5.7.2. Effects on Cell Cycle Events 195
5.7.3. Binding Studies 196
5.7.4. Effects on Protein Synthesis 197
5.7.5. Studies Using Mammalian Cell Lines 197
5.7.6. Resolving the Mode of Action of Azadirachtin 197
5.1. Introduction
The dominance of synthetic pesticides, which began
with the introduction of DDT in the 1940s, almost
displaced completely the natural pesticides used
before that time. Only pyrethrum and derris (the
active compound is rotenone) survived in specialized
uses. In the following half-century the problems of
persistence and toxicity of the synthetics grew and
regulation followed them. Slowly, one after the other
was restricted in use, until we have reached the point
where there are no longer available synthetic crop
protectants for certain uses. At the same time fundamental
research has uncovered entirely new ways
of dealing with pests that range from use of pheromone
traps through parasitoids to feeding deterrents.
Unique among these new discoveries is the
compound azadirachtin.
Azadirachtin is a colorless crystalline compound,
found in the seeds of the neem tree, Azadirachta
indica A. Juss. 1830. The compound is of great
interest because it is a powerful feeding deterrent
for a number of phytophagous insects, and has the
power, at parts per million concentration, to inhibit
growth and development of all insects ingesting it.
This substance, together with a few compounds of
closely related structure in the same seeds, provides
the most powerful natural pesticide discovered since
the era of synthetic pesticides. Its spectrum of activity
includes many other arthropods and even annelids
and nematodes. Yet it appears to have little or no
toxicity for vertebrates. Its isolation, structure determination,
synthesis, toxicity, mode of action, spectrum
of activity, and practical application have all
absorbed the interest of scientists of many disciplines