Development and emergence of Sitotroga cerealella (oliver) on stored yellow maize genotypes as affected by physical factors and grain quality

Abstract

Angoumois Grain Moth, Sitotroga cerealella (Olivier) (Lepidoptera:Gelechiidae) is a serious primary pest of stored grain in many parts of the world. A study was carried out in the laboratory to investigate the effects of grain physical and intrinsic properties, temperature, relative humidity, and grain moisture content on the development and emergence of S. cerealella. The experiment was arranged in completely randomized design with three replicates for each maize genotypes used. Daily temperatures and relative humidity were recorded at 8:00 and 16:00 GMT with a Temperature and Humidity Sensor, which was embedded in the polypropylene bag containing six maize genotypes and tied after each reading to prevent emerging insects from escaping. The number of S. cerealella that emerged was observed weekly. Angoumois grain moth emergence on stored husked maize ears began in the 3rd week through to the 6th week in storage. The moth emergence was higher in the season with higher percentage grain moisture content. A significant (P<0.05) difference was observed in percentage grain moisture within almost all the same genotypes during both major and minor seasons. Aburokokoo, Ahoodzin, and Obatanpa had significantly (P<0.05) higher mean numbers of the emerged moth from the 4th to 6th week. The grain physical and intrinsic characteristics such as surface area and weight of Aburokokoo, Ahoodzin, and Obatanpa were statistically different (P<0.05) from the other three genotypes. A significant positive relationship was observed between grain surface area, grain weight, density and total S. cerealella emerged. Abontem, Honampa, and GH2354 with smaller grain surface area and lower grain weight had smaller mean number of the moth emerging. Anthocoris nemorum (L.) an important generalist agricultural pest predator was observed to be associated with the moth when its population was high (13-63) but none when the moth population was very small (0-4) in store. The association between mean daily temperatures and relative humidity during the 6 weeks storage in both seasons was inversely proportional. About 88.25% of the variation in relative humidity depends on temperature. Key words: Maize, insect pest, grain hardness, predator, Anthocoris nemorum