Belg. J. Zool., 135 (supplement) : 179-181 December 2005 Evaluation of thiram and cinnamamide for protection of maize seeds against multimammate mice, Mastomys natalensis, in Tanzania Victoria Ngowo 1 , Loth S. Mulungu 2 , Jens Lodal 3 , Rhodes H. Makundi 2 , Apia W. Massawe 2 and Herwig Leirs 3,4 1 Rodent Control Centre, P.O. Box 3047, Morogoro, Tanzania 2 Pest Management Centre, Sokoine University of Agriculture, P.O. Box 3110, Morogoro, Tanzania 3 Danish Pest Infestation Laboratory, Skovbrynet 14, DK-2800, Kgs. Lyngby, Denmark 4 University of Antwerp Dept. Biology, Groenenborgelaan 171, B-2020 Antwerpen, Belgium Corresponding author : Victoria Ngowo, e-mail : vngowo@hotmail.com or ngowov@yahoo.com ABSTRACT. Farmers in Tanzania consider rodents to be the major vertebrate pest of maize, especially at planting and seedling stages and annual losses are high. We evaluated the potential of two seed-dressing compounds, thiram and cinnamamide, as rodent repellents to protect maize against damage by multimammate rats, Mastomys natalen- sis. In laboratory tests, the two compounds showed a strong repellent effect against M. natalensis and thus the potential to protect maize seeds. The two compounds were evaluated in maize fields using Randomized Complete Block Design (RCBD) with three replications. The results show that these repellents are effective for protecting maize seeds against multimammate rats in the field, but in locations with high population of Tatera leucogaster, seedlings are still damaged after emergence. Therefore, in such locations, other control measures, including applica- tion of rodenticides just before seedling emergence may be necessary. KEY WORDS : cinnamamide, economic loss, Mastomys natalensis, repellents, Tatera leocogaster, thiram, seed pre- dation. INTRODUCTION In Tanzania, farmers consider rodents to be the main vertebrate pest (LEIRS et al., 2003). It has been estimated that the annual economic loss due to rodents in maize fields may amount to 42.5 million dollars (MULUNGU, 2003), a loss that may be preventable by poisoning and trapping (STENSETH et al., 2001). However, poisoning and trapping techniques are frequently ineffective, environ- mentally hazardous and socially unacceptable or uneco- nomic (MYLLYMÄKI, 1987). Thus alternative methods to prevent rodent damage are needed. The deterrence approach to rodent control is not new (NOLTE & BARNETT, 2000, CAMPBELL & EVANS, 1985), although emphasis on chemical repellents as a means of reducing damage by rodents and other animals has increased in recent years. The need for materials to pro- tect maize at planting and seedling stage is generally rec- ognized (NGOWO et al., 2003). Ideal repellent seed dress- ing would prevent rodents from damaging the seed (SIMMS et al., 2000). The toxic effect on rodent should be minimal; otherwise they will act as rodenticides and basi- cally create vacant space that will attract other rodents. Moreover, the repellents must not have phytotoxic effects that would reduce germination rates (NOLTE & BARNETT, 2000, MYLLYMÄKI, 1987, CAMPBELL & EVANS, 1985). Preliminary laboratory studies from a wide range of botanic and synthetic repellents suggest that dressing maize seeds with thiram and cinnamamide can reduce damage to seeds by multimammate rats, M. natalensis. In general, repellents may be classified as either primary or secondary, according to their site of activity in the target species (ROGERS, 1978). Primary repellents provoke instantaneous responses through taste, olfaction, or irrita- tion of the buccal cavity. Secondary repellents produce distressing effects after eating (e.g. gastrointestinal malaise or other illness) which, if associated with a novel cue, may cause the subject to develop a conditioned aver- sion to a given food (GILL et al., 1995). Some repellent compounds have both primary and secondary activity (GILL et al., 1994). For example, the cinnamamide used in the current study is considered bitter and does not smell good (GILL et al., 1995). Thiram has a bad strong smell which probably has olfactory repellence in rodents. The present study, therefore, reports the results of field tests with thiram and cinnamamide. MATERIAL AND METHODS Study locations Two field experiments were conducted in December, 2002 and March, 2003 in Chunya (South -west Tanzania) and Mikese - Morogoro, (Eastern Central Tanzania), respectively, during the maize cropping seasons. In Chunya, maize is planted in November or December depending on the onset of rainfall, while in Mikese, it is planted in March. Initial trapping was carried out for three