Filter Paper Assays for Insecticide Research

In searching for new weapons in their fight against the destructive mountain pine beetle, scientists at the USDA Forest Service are experimenting using filtration techniques to create more effective insecticide treatment. It is estimated that 8% of forests in the United States are at risk to insect or disease outbreaks; among this percentage the mountain pine beetle is considered the biggest threat.

It’s necessary to find new solutions to protect these trees because of concerns about the future availability of one of the most commonly used insecticide chemicals, carbaryl, for environmental reasons. A study published this year examined the effectiveness of different concentrations of carbaryl along with two other known insecticides, cyantraniliprole and Cyazypyr (30 Scrabble points!). For this experiment the researchers performed two different assays, one involved exposing the beetles to insecticide with filter paper and one through a topical treatment. For both tests they used 1 mL of various concentrations of the insecticides along with 934-AH filter paper (1.5 micron pore size, 90 mm diameter) stored in a sterile petri dish and dried in a fume hood. In the filter paper assay, small holes were drilled into the petri dish to provide ventilation and captured beetles were placed on the filter paper. The health of the beetles was then assessed at regular intervals to determine the effectiveness of each insecticide concentration. In the topical assessment, the insecticide was applied directly onto the beetles which were then placed on top of the filter discs. The results of the filter paper assays, which the authors believes more closely approximates field conditions than topical assays, found that is possible that much smaller amounts of carbaryl could be effective in the field, which is good news for the environment as concerns over the toxicity of this chemical have grown. As such, the authors recommend that smaller concentrations of carbaryl be tried in the field. Take that, pesky beetles! Read the full report here