After about 8 months , the citronella loses its punch .
大约八个月之后,香茅失去了功效。
They 've made cardboard food cartons coated with a substance called citronella oil , which is extracted from grass .
他们在纸装食品的纸盒包装表面涂上一层名叫香茅油的物质,这种物质是从草中萃取得到的。
And past research has shown that bugs avoid the stink of citronella , along with the smells of other plant extracts , such as garlic and pine needles .
过去的研究表明,小虫避开香茅的恶臭味,但是趋向于其他植物如大蒜和松针的萃取物。
Botanical products that contain citronella , eucalyptus oil or melaleuca oil do repel mosquitoes , but only for very short period of time , and you have to reapply four times as frequently as a low-dose deet-based repellent , webb says .