Yellow insect traps to monitor the population of insects in controlled environment systems are available for free and can be obtained from the Research Greenhouse, DV1012 and DV3092D. These yellow insect traps are effective for insects including whiteflies, leafminers, sciarids, aphids, and many flying insects.
Below is an 11-minute video describing how to properly use these insect traps.
More information is also available here.