Effect Of Different Corn Stalk Returning Patterns On Population Of Overwintering Larvae Of The Asian Corn Borer Ostrinia Furnacalis(Guenée)

Corn is an important food crop in the world,which can be also used for feed and industrial raw materials,The Asian corn borer,Ostrinia furnacalis(Guenée),is one of the most important insect pest of corn in China.Its distribution area is extremely extensive,and the damage to corn is very serious.The older larvae of the Asian corn borer bore into corn stalk and feed on the pith,not only causing direct yield loss and quality decrease of the corn,but also resulting in corn stalk lodging,which would cause more yield loss by as the development of corn harvesting mechanization.Stalk returning to field is a kind of agricultural control of Asian corn borer which can reduce the number of overwintering larvae of Asian corn borer simply and efficiently,the population of Asian corn borer in the following year will sharply reduce,as well as improving the soil quality.The distribution of Asian corn borer in corn stalk affects the control efficacy for the Asian corn borer by stalk returning to field treatment,and the control effects of different stalk returning patterns on Asian corn borer was differents.The objectives of this work were to investigate the distribution of holes and the overwintering larvae in corn stalk,and also the control effects of different stalk returning patterns on overwintering larvae of Asian corn borer.The main results are as follows:The distribution of holes caused by the 1st and 2nd generation and also the overwintering larvae of Asian corn borer in corn stalk in Qiqihar,Gongzhuling and Wuqiao(the 2nd and 3th generation holes,respectively)were investigated in 2017 and 2018,respectively,Results showed that the holes of 1st generation was mainly in the middle portion of the corn stalks for 69.6%,the 2nd generation mainly in the lower portion for 41.2%,the distribution of overwintering larvae of the Asian corn borer were mainly in the middle portion and the lower portion for 40.6% and 36.6% in Qiqihar,respectively.The distribution of holes of 1st and 2nd generation was mainly in the middle portion of the stalk for 47.3%and47.7%,the overwintering larvae was mainly in the lower portion for 63.2% at harvest,and in the lower portion increased to 75.1% in December of 2018,in the root portion increased to 24.3% in April of 2019,respectively,in Gongzhuling.In Wuqiao,the holes of 2nd generation and the 3rd generation was mainly in the upper portion of the stalk for 77.1% and 67.4%,individually,the overwintering larvae was mainly in the middle portion for 53.6%.The results showed that the distribution of holes caused by Asian corn borer in the 2nd generation was lower than that of holes in the 1st generation,the overwintering larvae of Asian corn borer mainly distributed in the middle and lower portion of the stalk and had a downward trend in winter and following spring in northeast corn region.The distribution of holes in the 3th generation was mainly in the middle portion,the overwintering larvae of Asian corn borer mainly distributed in the middle portion in summer corn region.In the number of the overwintering larvae of Asian corn borer were compared by different stalk returning patterns with corn stalk taking out of the cornfield,the corn stalk smash returning to field combined with intensive cultivation,corn stalk taking out of field,the remaining high stubble,the stalk covered,the stalk chopped and mixed with soil and the ploughing chopped corn stalk under soil,the result shows,the number of live larvae were significantly decreased to by 93.17%,93.32%,57.53%,70.73%,93.66%,89.94%,after treatment,respectively.The effect for for depressing the overwintering larvae of the Asian corn borer by the corn stalk smash returning to field combined with intensive cultivation,the stalk chopped and mixed with soil,and the ploughing chopped corn stalk under soil were much better than that of high stubble and stalk covered,(p < 0.05).There was no significant difference in number of live larvae before and after overwintering among the different treatments,except that of the remaining high stubble,which was 9 live larvae per 100 stalks.And there was almost no live larvae in the treatment of corn stalk smash returning to field combined with intensive cultivation.The results showed that the effect of the remaining high stubble on depressing the number of overwintering larvae of Asian corn borer was poor.The mortality of the overwintering larvae of Asian corn borer in stalk before and after stalk returning was investigated.The total mortality and mortality caused by mechanical injury of overwintering larvae in the stalks of straw returning treatment was significantly higher than that of untreated corn stalks before diapause termination(p < 0.05),however,there was no significant difference in after diapause development.The results showed that mechanical damage during the stalk returning process can further reduce the number of overwintering Asian corn borer.