EVALUATION OF RICE HUSK AND MELON SHELL POWDERS IN THE CONTROL OF CALLOSOBRUCHUS MACULATUS (FABRICIUS) AND SITOPHILUS ZEAMAIS (MOTSCHULSKY)

Abstract

Grains and pulses undergo maximum damage in storage due to weevil attack. Many plant parts have been reported potential protectants with limited application in stores .This study focused on what are mostly referred to as agricultural wastes, like powders and ashes of rice husk and melon shell for the control of cowpea bruchid, Callosobruchus maculatus and the maize weevil, Sitophillus zeamais. The study was carried out under laboratory conditions in Cocoa Research Institute of Nigeria Ibadan, Nigeria. Powders of rice husk and melon shell showed a minimal control on both weevils ashes of rice husk and melon shell showed a significant control on both weevils. In the treated cowpea, Rice Husk Ash (RHA) registered above 80% mortality followed by Melon Shell Ash (MSA) with about 70%; Rice Husk Powder (RHP) with about 40% and MSP more than 20%, unlike the untreated cowpea seeds that recorded 0% adult mortality. Maximum mean number of eggs (101), were laid by by C. maculatus in the untreated cowpea seeds compared to that on the treated seeds (Rice Husk Powder, RHP - 43.91; Melon Shell Powder, MSP - 52.38; Rice Husk Ash, RHA - 0.95 ; Melon Shell Ash, MSA - 29.95.Mean effect of powders and ashes of rice husk and melon shell on oviposition of C. maculatus showed that Rice Husk Ash, RHA had significantly higher percentage of 99.04, Melon Shell Ash, MSA-70.44%; Rice Husk Powder,RHP-56.53% and Melon Shell Powder, MSP with 48.81%. Number of adult C. maculatus that emerged from the control treatment (78.5) was significantly higher than other treatments. Adult emergence recorded with Rice Husk Powder was 34.43; Melon Shell Powder - 38.24; Melon Shell Ash – 25.0 and Rice Husk Ash -0.33). The study also showed that treated Cowpea seeds were protected than the untreated seeds. Seed weight loss was lower on treated cowpea seeds irrespective of the treatment application compared to the control treatment. On the treated cowpea seeds, seed weight loss ranges between 0 - 0.34% which is lower than the control treatment where 1.17% was recorded. Significantly lower numbers of cowpea seeds were holed in seeds treated with Rice Husk Ash where weevil perforation index was 0.80. However the number of holed seeds was higher on cowpea seeds treated with Rice Husk Powder - 34.16 and Melon Shell Powder – 34.10, followed by Melon Shell Ash -24.11, while both Rice Husk Ash and the standard control of P.guinensis recorded lesser than 1 . In this study, maize grains treated with Rice Husk Ash and Melon Shell Ash both had close to 100% death of adult S. zeamais at 96hrs, Rice Husk Powder had 42.4% and Melon Shell Powder 33.8% but the control had 0.8% kill. Control seeds recorded maximum number of adult emergence (20.00) followed by Melon Shell Powder - 11.81, and Rice Husk Powder - 11.38. Furthermore Rice Husk Ash and Melon Shell Ash completely protected the grains with zero adult emergence. Percentage seed weight loss was higher in the untreated control (0.30) followed by Rice Husk Powder -0.24 and Melon Shell Powder - 0.23. Both Rice Husk Ash and Melon Shell Ash recorded zero percentage seed weight loss. Mean percentage germination was high in the treated grains, Rice Husk Ash - 62.86%; Melon Shell Ash - 55.71%; Rice Husk Powder - 51.90%; Melon Shell Powder - 47.14% but significantly low in the control (25.83%). Rice Husk Ash and Melon Shell Ash would be safer alternatives in the control of storage pest of cowpea C.maculatus and storage pest of maize S zeamais.