From MSU Extension:
Do you have pesticide-resistant spider mites, thrips, whitefly or aphids? Have you attempted to use biological control agents (BCAs) and given up in favor of traditional control methods? The frequent use of insecticides in the greenhouse has led to many pesticide-resistant insects. For example, control of whitefly on poinsettias was more difficult than ever during the 2012 growing season. Some producers are moving to a biological control program because of the decreased effectiveness of traditional methods while some want to reduce the risk of accidental exposure of their employees to chemicals. No matter what the reason is for the switch, there are four critical steps to starting a biological control program.
Unfortunately, there is no half-way when considering a biological control program: if you are considering making the switch from traditional methods to the use of biologicals for one pest, you should consider a complete program of biologicals. While there may be “compatible” traditional sprays with one type of BCA, it might hinder the population of BCA’s for a different pest. Tools such as the Side Effects Manual from Biobest examine the active ingredients of sprays and show how they hamper populations of beneficials and how long the residuals will last. These kinds of tools will quickly tell you that any spray could knock your whole beneficials program.
In addition, know your producer and ask questions. When receiving cuttings, it is important to scout for insects. In addition to examining your cuttings for insects, understand the pesticides or fungicides used to treat the stock plants from which your cuttings came. Residuals can be common on cuttings, but vary with producer. For example, researchers found that poinsettia cuttings going to 10 different growers in Canada had residuals of 24 active ingredients of pesticides and 20 fungicides. While some residuals are short-lived and have no effect on BCAs, some may prevent BCAs from becoming established by the first generation of the pest insect. By asking questions of your producer, you will have some insight on the types of residuals that might be present on your cuttings that could be hampering your efforts to get your biological control program off of the ground. In general, all insecticides are harmful to beneficials and residual effects may last as long as six months.
Click here to read about the last two steps.