The focus of this study was to determine the efficacy of the different particle sizes of the powder of three plant materials, African Nut-meg (Monodora myristica), Black pepper (Piper guineense) and dry bud of Cloves (Eugenia aromatica) in the control of Dermestes maculatus infestation on stored dried African mud catfish, Clarias gariepinus. Each plant material was pulverized, sieved into 0.5 mm and 0.4 mm particle-sizes, rubbed at 5 g of powder onto the body of 55 g dried fish and placed in Kilner jar in triplicates. The weight loss, adult / larvae emergence and adult mortality of treated fish were determined. The results showed that 0.4 mm particle size of the powder of P. guineense and E. aromatica prevented the infestation of D. maculatus as demonstrated by low fish weight loss, low level of adult / larvae emergence and high mean value of adult insect mortality. Higher number of larvae emergence and weight losses were recorded in the fish exposed to 0.5 mm of each plant powder and 0.4 mm of M. myristica. The study revealed that stored catfish could be treated with smooth particle sizes of Piper guineense and Eugenia aromatica, and can significantly serve as protectants of smoked C. gariepinus against Dermestes maculatus infestation.