What are crack and crevice (C&C) treatments and why should I care? Control of pests increases and pesticide use is reduced when crack-and-crevice straws are used and inserted 1/4 inch into a crack during application. Moving the straw along the length of a crack as part of a C&C treatment improves the coverage of liquid insecticide on surfaces contacted by cockroaches and other pests. Crack-and-crevice treatments are usually made with a tip extension on the nozzle. The most common is a 6-inch, flexible-plastic tip. These tips, or straws, are more effective than fan sprays in treating cracks infested with German cockroaches and other pests that live in hidden areas.