Evaluation of maize varieties for resistance to maize weevil (Sitophilus zeamais Motschulsky) (Coleoptera: curculionidae) under laboratory condition

Abstract

Maize is an important crop ranking second in world grain production only preceded by wheat and it is an important component of agriculture and food systems all over the world. A study was conducted with the objective to determine the resistance of maize varieties to maize weevil, Sitophilus zeamais. It was conducted at Jimma University College of Agriculture and Veterinary Medicine in entomology laboratory at room temperature of 25 to 27°c and 40 - 60 % R.H in 2011/2012. The maize varieties were collected from Bako and Holeta Agricultural Research Centers, Ethiopia and the local variety was collected from Jimma area. The varieties are currently under production in different parts of Ethiopia. About 300g seeds from each of the maize varieties were placed in a one liter glass jar with brass screen lids allowing ventilation and preventing escape of the weevils. No choice test method in which the weevils were introduced to each jar was used for the study. The treatments were arranged in a completely randomized design (CRD) with three replications. A total of 13 maize varieties were screened for their relative resistance to S. zeamais. The index of susceptibility was used to classify the varieties in to different reaction categories. Varieties were significantly different in terms of susceptibility index (at 5% probability level). Only the standard checks variety, ‘BHQP-542’, had 3.5 index of susceptibility and was regarded as resistant variety to maize weevil attack. However; most of the varieties, namely BH660, BH670, BH543, BHQPY545, Gibe-1, Gibe-2, Wanchi, Argane, Hora and Local variety-Orome had index of susceptibility 4.6, 5.3, 4.7, 4.8, 4.9, 4.8, 5.2, 5.7, 5.2, 6.0 respectively and are regarded as moderately resistant to maize weevil attack. Two varieties (BH661 and Kuleni) had index of susceptibility 7.11 and 7.09 respectively and are regarded as moderately susceptible varieties to maize weevil attack. The standard check variety produced low numbers of F1 progenies (51.33), had a high median developmental time (48.33 days), a low percentage of seed damage (15.85%), less production of grain dust (powder (0.03%)), low percentage of seed weight loss (4.11%) and high percent weevils mortality (14.24%) and seed germination (93.66 (undamaged) & 86.60% (damaged)).Weevils progeny emergency is significantly and positively associated with seed damage and weight loss but inversely with median development time. The use of resistant varieties in insect pest management is an ecofriendly and cost effective means that should be promoted for S. zeamais management in maize especially for small-scale farmers in the tropics.