2012年三代黏虫大发生原因初步分析

Preliminary analysis of the outbreak of the third-generation armyworm Mythimna separata in China in 2012

黏虫是我国粮食作物重要迁飞性害虫之一,2012年8月上旬三代黏虫在我国华北北部和东北部分地区突然暴发,发生面积和为害程度为近十年罕见。本文通过探照灯的多年连续监测,结合气象因素、迁飞高峰期的天气背景分析和迁飞路线的轨迹模拟,探讨了2012年三代黏虫大发生的原因。分析结果表明:在二代已积累较高虫源量的基础上,7月中下旬华北和东北地区适宜温度和频繁降雨为二代成虫迁飞、繁殖提供了有利条件,适宜的寄主为三代幼虫取食提供了充足的食物来源,以上是导致华北和东北地区三代黏虫大发生的两个主要因素。虫源分析显示华北北部和辽宁中西部重灾区虫源主要来自本地,部分虫源来自重灾区的周边地区,受降雨和下沉气流影响大部分集中降落华北北部和辽宁中西部地区,一部分继续迁飞进入东北地区。东北重灾区虫源大部分来自本地,受偏西气流和降雨的影响,东北地区二代成虫未形成有效迁出,黑龙江北部二代成虫在气流运载下向南迁飞,受锋面天气影响降落在黑龙江、吉林交界处,与华北地区迁入的成虫汇集后,不断进行短距离迁飞扩散,聚集为害,造成东北地区大面积发生,局部严重发生。

The armyworm Mythimna separata is one of the serious migratory pests of food crops in China.A sudden outbreak of the 3rd-generation larvae occurred in the northern and northeastern China in early August 2012.The areas of occurrence and the degree of damage were the most serious in recent ten years.Based on long-term monitoring using searchlight traps,combined with meteorological factors and trajectory simulation,this study was conducted to analyze the causes of the outbreak of the 3rd-generation armyworm in 2012.The results showed that low temperature and frequent rainfall in late July provided favorable conditions for the breeding of the 2nd-generation adult and suitable host for adequate food sources for the 3rd-generation larvae.These were main factors leading to the outbreak of armyworms.Trajectory simulation showed that the pest sources of North China and Midwest of Liaoning Province were mainly from the local and partially from surrounding areas.Most adults were forced to land by rainfall and subsiding air,and part of the adult continued to fly to the northeast China.The main source areas of 2nd-generation moth immigration in northeast China were local,and the secondary source area was northern China.Because of westerly flow and rainfall in late July,the local 2nd-generation moths did not form an effective emigration;the 2nd-generation moths in northern Heilongjiang mainly landed at the junction of Heilongjiang and Jilin provinces as a result of wind shear associated with heavy precipitation.Short-distance migratory and concentrated landing were the main impact factors causing the damage in northeastern China.