I used the chart that suggested a 1/2 tbs per quart and sprayed the plant from top to bottom and under the leaves only to come back a few hours later and find just as many on there as they started alive and crawling around. It was my understanding that it kills on on contact and its should only be used every 7-10 days. As much as I sprayed I figured there shouldnt be many left but there were. Did I use the wrong ratio or do I need to spray again?