Activity and Biological Effects of Neem Products Against Arthropods of Medical and Veterinary Importance

Journal of the American Mosquito Control Association' 15(2):133-152, 1999 Copyright O 1999 by the American Mosquito Control Association, Inc. ACTIVITY AND BIOLOGICAL EFFECTS OF NEEM PRODUCTS AGAINST ARTHROPODS OF MEDICAL AND VETERINARY IMPORTANCE MIR S. MULLA ENN TIANYUN SU Depdrtment of Entomobgy, University of Califomia, Riverside, CA 92521-O314 ABSTRACT. Botanical insecticides are relatively safe and degradable, and are readily available sources of biopesticides. The most prominent phytochemical pesticides in recent years are those derived from neem trees, which have been studiedlxtensively in the fields of entomology and phytochemistry, and have uses for medicinal and cosmetic purposes. The neem products have been obtained from several species of neem trees in the family Meliaceae. Sii spicies in this family have been the subject of botanical pesticide research. They are ATadirachta indica A. Jrtss, Azadirachta excelsa Jack, Azadirachta siamens Valeton, Melia azedarach L., Melia toosendan Sieb. and Z1cc., and Melia volkensii Giirke. The Meliaceae, especially A. indica (Indian neem tree), contains at least 35 biologically active principles. Azadirachtin is the predominant insecticidal active ingredient in the seed, leaves, and other parts of the neem tree. Azadirachtin and other compounds in neem products exhibit various modes of action against insects such as antifeedancy, growth regulation, fecundity suppression and sterilization, oviposition repellency or attractancy, changes in biological fitness, and blocking development of vector-borne pathogens. Some of these bioactivity parameters of neem products have been investigated at least in some ipecies of insects of medical and veterinary importance, such as mosquitoes, flies, triatomines, cockroaches, fllas, lice, and others. Here we review, synthesize, and analyze published information on the activity, modes of action, and other biological effects of neem products against arthropods of medical and veterinary importance' The amount of information on the activity, use, and application of neem products for the control of disease vectors and human and animal pests is limited. Additional research is needed to determine the potential useful- ness of neem products in vector control programs. KEY WORDS Meliaceae, neem, azadirachtin, insecticides, mosquitoes, flies, triatomines, cockroaches, fleas, lice, pest control INTRODUCTION (Mulla 1997). Interest in botanical insecticides start- ed in the early 1930s and continued to the l950s The extensive and widespread use of synthetic in- (Campbell et al. 1933; Jacobson 1958), but the insecticides during the past half century, since the dis- terest in their development and use was phased out covery of DDT during World War II, for the control when synthetic insecticides appeared on the scene. of household, agricultural, and sylvan pests, as well Interest in the development of natural products has as human disease vectors has caused some concerns been revived during the last 2 decades. Thus far regarding the toxicity and environmental impact of about 10,000 secondary metabolites or phytochem- some of these agents. Some inherent features and use icals have been isolated, but their total number is patterns of the conventional synthetic insecticides estimated to be much higher, close to 500,000 that lead to these concerns are toxicity to mammals (Ascher 1993). More than 2,000 plant species re- including livestock, fish, birds, and beneficial organ- portedly possess chemicals with pest control prop- isms; human poisoning, especially in Third World erties (Ahmed et al. 1984), and among these about countries; adverse effects on the environment, caus- 344 species ofplants have been shown to have some ing contamination of soil, water, and air; resurgence degree of activity against mosquitoes (Sukumar et of insect pest populations because of the emergence al. 1991). The most prominent phytochemical pes- and widespread occurrence of physiologic resistance ticides studied in recent years are those based on the to conventional insecticides; the high cost of the de- neem prducts, which have been researched exten- velopment of new synthetic insecticides, which puts sively for their phytochemistry and exploitation in the new agents out of the reach of pest control pro- pest control programs. This paper presents a concise grams in Third World countries; and not meeting the review of recent advances in research on the activity, modern criteria of use in integrated trrestmanagement efficacy, and potential uses ofneem products for the programs. control of arthropods of medical and veterinary im- Because of these problems and concerns, the portance. search for new, environmentally safe, target-specific insecticides is being conducted all over the world. OVERVIEW OF NEEM PRODUCTS To find new modes of action and to develop active agents based on natural plant products, efforts are Neem tree being made to isolate, screen, and develop phyto- Six species in the family Meliaceae have been chemicals possessing pesticidal activity. These cat- studied for pesticidal properties in different parts of egories of pesticides are now known as biopesticides the world. They are Azadirachta indica A. Juss 133 t34 JounNer- op tHe AN4BRrcnNMosguno CoNTRor- AssocrnrtoN VoL. 15,No.2 (syn. Melia azadirachta, Antelaea azadirachta\. have been reported to contain AZ (Morgan and commonly known as the neem tree, Margosa tree, Thornton 1973). The detailed chemistry of AZ cart or Indian lttlac1'Aaadirachta excelsa Jack (syn. A. be found in Ley et al. (1993). integrifoliola), called the Philippine neem tree or In addition to AZ, a number of other active in- marrango; Azadirachta siamens Valeton, or the Si- gredients have also been isolated and identified from amese neem tree or Thai neem tree: Melia azedar- different parts of the neem tree. Compounds such as ach L., commonly known as Persian lilac, china- salannin, salannol, salannolacetate, 3-deacetylsalan- berry, Australian bead tree, Chinese umbrella tree. nin, azadiradion, l4-epoxyazadiradion, gedunin, or pride of India; Melia toosendan Sieb. andZrtcc.; nimbinen, deacetylnimbinen, 23-dihydro-23p-meth- and Melia volkensii Giirke. Varieties of these oxyazadirachtin, 3-tigloylazadirachtol, and l-tigloyl- named species occur, some of which have been as- 3-acetyl- 1 1-methoxyazadirachtin were isolated from signed species status in some countries. Generally, oil extracted from neem seed kernels (Schmutterer the neem tree is referred to A. indica. However. 1990). Vilasinin derivatives, meliantriol, azadiradi- herewith we use neem products for all of the bio- one, l4-epoxyazadiradione, 6-0-acetylnimbandiol, 3- active components originating from this group of deacetylsalannin, and deacetylazadirachtinol were plants in the family Meliaceae. Plants in the family also recovered from neem seed oil (Schmufterer Meliaceae, especially A. indica, contain at least 35 1990), whereas nimocinolide and isonimocinolide biologically active principles (Rao and Parmar were recovered from fresh leaves (Siddiqui et al. 1984) and these products have many industrial, me- 1986). Some other compounds, such as alkanes, dicinal, and pesticidal uses. Various components of were isolated from dried leaves (Chavan 1984, the tree have potential uses in toiletries, pharma- Chavan and Nikam 1988), and nonterpenoidal con- ceuticals, the manufacture of agricultural imple- stituents, isocoumarins, coumarins, and saturated hy- ments and furniture, cattle and poultry feeds, nitri- drocarbons were recovered from fresh, uncrushed fication of soils for various agricultural crops, and twigs (Siddiqui et al. 1988). Although the bark, pest control (Koul et al. l99O). heartwood, leaves, fruit, and seeds of neem have been investigated chemically for their main biocidal components, the renewable parts (seeds and leaves) Active ingredients received major research attention. A number of bioactive components have been isolated from various parts of the neem ffee. These Mode of action chemical compounds have different designations, among which azadirachtin (AZ) (C..ItoO,) is the Neem products are capable of producing multiple major component. The insecticidal properties of effects in insects such as antifeedancy, growth reg- products from the neem tree were flrst reported by ulation, fecundity suppression and sterilization, ovi- Chopra (1928). Forty years later, AZ, a steroidlike position repellency or attractancy, and changes in tetranotriterpenoid (limonoid), was isolated by But- biological fitness. These aspects are discussed in terworth and Morgan (1968) from A. indica. How- detail in recently published comprehensive reviews ever, it was not until 1987 that the chemical struc- (Ascher 1993; Mordue and Blackwell 1993; ture of AZ was completely elucidated by Kraus et Schmutterer 1988, 1990). Most of the information al. (1987). Azadirachtin is the predominant insec- reviewed in these papers was gathered with regard ticidal active ingredient in the seeds of the neem to phytophagous insects. Some of these phenomena tree. The AZ content in neem oil was highly cor- are briefly reviewed and discussed below. related with its bioactivity against test insects (Is- Antiftedancy.' Chemical inhibition of feeding has man et al. 1990). A marked difference has been been studied in detail for a few phytophagous in- reported in the yield of AZ from neem seeds from sects. The mechanism of feeding inhibition could different geographical origins (Schmutterer and Ze- be a blockage of the input from chemoreceptors

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