Study On The Sitophilus Zeamais Motschulsky In Wheat And The Harm Critical Values

In this paper, wheat were infected with different density of Sitophilus zeamaisMotschulsky in sealed storage environment,we study the carbon dioxide concentration, bulkdensity, worm-eaten rate, fatty acid and flour quality indexes of the wheat during4monthesin different time.Then discuss the relationship between insect infection degree and graincondition,and grain quality,inorder to through the non-contact manner monitor insectoccurrence. The result were as following:The results involve in that in the chamber with no insects the concentration of carbondioxide went up from0.046%to0.752%at20℃and that did from0.044%to0.820%at25℃. In the sample with two adults per kilogram of wheat the concentration increased to5.638%at20℃and to7.505%at25℃. For the grain with ten adults per kilogram theconcentration risen to17.381%at20℃and to18.244%at25℃, severally Whereas theobvious ascend of the gas concentration was existed in the initial ten days for all infestedgrain. Furthermore there was a positive correlation between concentration of carbon dioxideand insect density, temperature and infected time. The concentration change of carbondioxide in sealed environment of grain is likely to reflect the insect infection state in somedegree.In the under20℃after the120d,Sitophilus zeamais Motschulsky density no insect andtwo adults per kilogram of wheat was little changed. When the insect number was five adultsper kilogram of wheat,the bulk density of wheat746.3g/L was reduced from767.7g/L to, thecritical value appears in the110d. When the insect number was ten adults per kilogram ofwheat,the bulk density of wheat740.0g/L was reduced from767.7g/L to, the critical valueappears in the80d. In the under25℃after the120d, When the insect number was ten adults,the critical value appears in the60d.In the chamber with no insects the concentration of fatty acid went up from36.401mgKOH/100g to50.633mgKOH/100g at25℃, For the grain with ten adults per kilogram thefatty acid risen to74.627mgKOH/100g. Infection of insect pests has important effects onfatty acid value in wheat. And up under a temperature of25℃higher fatty acid value of wheatin wheat sample rate significantly greater than20℃samples.In20℃，the storage time of wheat without insects is obviously in positive correlation with wheat’s water absorption and Degree of softening, and in negative correlation withDevelopment time, stabilization time and farinograph quality. In25℃，the storage time ofwheat without insects is obviously in positive correlation with wheat’s water absorption andDegree of softening, and in negative correlation with Development time, stabilization timeand farinograph quality.Temperature is a key factor to quaicken the pest reproduction rate. Asthe temperature climbs, the reproduction rate of Sitophilus zeamais Motschulsky becomesfaster.