J. Korean Soc. Appl. Biol. Chem. 53(5), 598-604 (2010) Article Effects of Azadirachtin and Neem-based Formulations for the Control of Sweetpotato Whitefly and Root-knot Nematode Ohn Mar Lynn † , Woo-Geun Song, Jae-Kyoung Shim, Jang-Eok Kim, and Kyeong-Yeoll Lee* School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea Received February 12, 2010; Accepted May 31, 2010 Toxicity of the plant-derived natural pesticide azadirachtin and two types of commercial neem (Azadirachta indica A. Juss)-based formulations, Neema (liquid type) and Neema-plus (pellet type), were evaluated based on the mortality rate and developmental inhibition of the sweetpotato whitefly (Bemisia tabaci) and root-knot nematode (Meloidogyne incognita). In a laboratory assay, when B. tabaci adults were fed leaves containing 5 or 10 ppm of azadirachtin solutions, the rates of female oviposition, subsequent egg hatch, and adult eclosion were significantly reduced to 23.1, 53.2, and 26.6% of the control, respectively. At a tomato greenhouse, the rates of adult colonization, oviposition and egg hatch were reduced to 78.2, 47.0, and 71.2% by Neema foliar spray and 31.3, 34.1, and 66.8% by soil treatment with Neema-plus relative to the control, respectively. When isolated soil nematodes were exposed to various concentrations of azadirachtin, Neema, and Neema-plus, the immobility of juvenile nematodes showed no change at 2 h after treatment, whereas a reduction of 36.3% was observed at day 1 with 10 ppm of azadirachtin. Nevertheless, the effects of neem formulations were faster and much higher than those of azadirachtin. At a cucumber greenhouse, soil treatments with neem formulations significantly reduced the numbers of soil nematodes and plant root-knots; the reduction with Neema was 12.1 and 9.0%, and with Neema-plus 26.4 and 24.6% of the control, respectively. Furthermore, soil treatment with Neema- plus greatly improved the growth of cucumber plants in nematode-infested pots. These results showed that azadirachtin and neem-based formulations were highly effective on the developmental inhibition of both whiteflies and root-knot nematodes. Thus, soil application of the neem-based formulations would be applicable for the control of both leaf-sucking and soil pests. Key words: azadirachtin, Bemisia tabaci, neem, plant-derived pesticides, root-knot nematodes The neem tree (Azadirachta indica A. Juss) is the most well known plant with powerful insecticidal properties since its discovery in 1966 [Mordue (Luntz) et al., 2005; Morgan, 2009]. Although various parts of the neem plant have been used for pest control, neem seeds have been the main source for the production of commercial neem formulations [Copping and Duke, 2007]. Neem extract contains various compounds that are toxic to insects, among which azadirachtin, a triterpenoid of the limonoid class, is the most active compound for the inhibition of insect growth and development [Schmutterer, 1990; Ascher, 1993; Mordue (Luntz) and Blackwell, 1993]. It is effective on many groups of arthropods, as well as nematodes and annelids, but has no toxic effect on vertebrates [Mordue (Luntz) et al., 2005]. The roles of azadirachtin have been identified in the physiological systems of digestion, endocrine, and reproduction of insects [Mordue (Luntz) et al., 2005]. Azadirachtin has a strong antifeedant activity on various phytophagous insects. In addition, when larval insects ingest this compound, their growth and development are inhibited due to the blocking of the biosynthesis of insect hormones, such as ecdysteroids. Furthermore, when insects ingest this compound, the development of reproductive organs, such as the ovary and testis, is significantly inhibited, and the fertility and fecundity of the adults are also reduced. Recently, there has been a resurgence of research devoted to improving the insect- controlling efficacy in practical applications for a specific pest in the field. In addition, recently developed molecular Present address: Department of Entomology, Yezin Agricultural University, Myanmar *Corresponding author Phone: +82-53-950-5759; Fax: +82-53-950-6758 E-mail: leeky@knu.ac.kr doi:10.3839/jksabc.2010.092