The Evolutions Of Corn Borer’s Developmental Rule And The Study On The Application Of Trichogramma Control In Qiqihar Area

The corn planting area in Qiqihar shares the highest proportion around Heilongjiang province,and this has turned up an increasing tendency year by year. In2013, its area had increased to146hm2in Qiqihar (the highest proportion on record), simultaneously the harm of corn borer here wascomparatively serious, whose amount of live overwintering larvae became more than125perhundred plants on average and this amount could even soar over300in serious year. InHeilongjiang province, Trichogramma dendrolimi had been widely applied to control corn borer’sdamage, and the effect was around60%. With the climate warming and the change of cultivatingstructure in recent years, the development rule towards corn borer had varied accordingly.According to some surveys, the harm of corn borer had developed from its original first generationto its incomplete second generation and its complete second generation, furthermore the firstgeneration and the second generation became pest sources to each other and harmed each other aswell, which increased the pest damage greatly. Therefore, in order to improve the control effectcorn borer, it is important to control its both generations, adjust its control times and releasingamount of Trichogramma dendrolimi and compare the control results of different subspecies ofTrichogramma dendrolimi，in which to investigate its optimum control method.Obviously temperature and relative humidity are closely related to agricultural diseases andpests, therefore it is available to involve the former factors in the outbreak of agricultural diseasesand pests and study their relations comprehensively. The life activities of insect, like its survivaland reproduction, its growth and development, its metabolic rate and its migration and spread, aredirectly influenced by temperature, thus it has a great significance to study the influence of climatechange on the insect’s ecological mechanism, to construct the climate warming effects on insect,and to improve the accuracy of pest prediction and the scientificity of pest control. As is known therelation between crops and pests which is closely related to global warming has become a researchfocus to study the rule towards the outbreak and development of pest, therefore it is meaningful tohave a further research on the above topic in explicating the pests towards global warmingresponse mechanism, improving preventions towards the outbreak of pest and exploring its newprevention techniques, and maximize the effectiveness of the current control techniques as well.According to the meteorological datas of Qiqihar in last15years, the thesis applies SAS softwareto analyze the amount of corn borer larvae and its pupation per hundred plants in eachcorresponding year, and then gets the results that the former two parameters are significantlyassociated with the climate conditions. In this paper, the test applies Trichogramma ostriniae,Trichogramma chi and Trichogramma dendrolimi to control corn borer. Trichogramma ostriniaecould effectively decrease the field population of corn borer, for the egg parasite rate highestreached to90.6%while the average control effectiveness to98.4%correspondingly. Comparedwith Trichogramma ostriniae, Trichogramma dendrolimi was less effective, with the statistic that the egg parasite rate highest reached to62.9%while the average control effectiveness to74.8%correspondingly. In terms of the test data, it would breed the corn borer second generation in thearea of Qiqihar, and this pest would last a long developmental cycle because of its physical habitsand its regionalities, which turned out to be blending mode of occurrence with the first generationand the second generation, but mainly the second generation. The second generation takes itsgenesis if completely incubating before July10th and comes into its spawning peak around August10, which can cause severe damage at the corn milk-ripe stage. The first generation of corn borermainly harms plants’ leaves and stems, while the second generation mainly to filaments, tasselsand stems, and these two damage waves will turn to serious yield loss. Therefore, it is urgent todifferentiate the two generations of corn borer that varied in correspondence with climate change,so as to promote the effectiveness of this pest control and provide available referential data.In terms of research results, if Trichogramma’s releasing amount reach to30000, increasingreleasing times （early to June30th for the first time and last to August17th for the last time）can widely improve the control effectiveness corn borer control. When the egg parasite ratehighest reached to98.4%, the average control effectiveness can turn out to be90.6%correspondingly, while the traditional releasing way, when the the egg parasite rate is70-85%, itsaverage control rate is only65.8%. Therefore it is natural to get the conclusion that leadingTrichogramma’s releasing time and increasing its releasing times can improve the effect ofartificial releasing Trichogramma against corn borer in Qiqihar area.