The investigation, he wrote, had been challenging because there were very few research labs able to test for the chemical later identified as the cause of the smell.
他在信中写道，检查遇到了困难，原因是，对于经调查确认造成这种气味的化学物，几乎没有实验室能够测试得出来。
Method: Density investigation: stick catch; Chemical methods: applying high effect cockroach bait.
方法：密度调查采用粘捕法，化学防制采用高效灭蟑毒饵。
Methods:adhesive killing method for density investigation, and cockroach gel bail for chemical control.
方法：密度调查采用粘捕法，化学防治采用高效灭蟑毒饵；
应用推荐