So what can be realistically be done to deal with pesticide resistance once it happens? When pests develop resistance to pesticides, it is a difficult challenge but in most cases not an impossible one. The key to the effectiveness of these management practices include cost, time, markets and climate. Also remember we are speaking about resistance developing in insects and diseases, not just weeds.
• First, everything possible needs to be done to start with a pest free planting environment which is easier said than done.  It is most practical for weed control. The idea is to provide the crop every opportunity to outcompete and/or outgrow the pests. This has little effect on pests that move in from a distance such as leaf rust or head moth.
• Crop Rotations – These are key to helping controlling pests in the first place and helping prevent the onset of resistance. However, crop rotations are a primary tool once resistance has developed, especially the more host specific the pest is. And the longer and more diverse the rotation the better as it better disrupts pest life cycles. While most beneficial for insects and diseases, it also aids in managing weeds. The length and diversity possible is a function of several factors: climate, market, and cost. Rotation possibilities increase as you move from the Colorado border east due to climatic factors, primarily rainfall, temperature and length of growing season. A crop may be perfect for a rotation in an area but without a practical market, it is of little value. Again, a crop may be perfect for a rotation but if the cost of producing the crop (primarily equipment and inputs) is greater than the value of the crop, it’s not practical. Finally, the producer needs to develop a crop rotation that works from a time and crop management standpoint.
• Pesticide Rotation – Rotating the mode of action, even after resistance develops, can help control pests. A major factor here is often cost or factors such as pesticide persistence (especially for herbicides).
• Except under no-tillage, tillage, both preplant and cultivation, can help, especially with weed control.
• Burning – Like tillage, burning isn’t preferred but a well-timed occasional burning of residue can greatly aid in pest control.
• Cultural Decisions – This includes everything from row spacing and plant population to planting date. Here the goal is to tap dance around pests by disrupting them in time and space. In English that means by adjusting cultural variables, a producer aims to produce an unsuitable pest environment or actually have the pest and crop miss each other in time.
• Multiple Control Techniques – Here a producer doesn’t rely on a single method of control or mode of action but evaluates the situation and determines a combination of techniques to “override” the resistance while maintaining the environment.
• Nothing – This is one not likely to be done often for obvious reasons. It is as simple as the word itself and most likely to be used with more mobile pests such as insects and certain windborne diseases. Simply, a producer stops using any chemical control or at least the mode of action where resistance has developed. The idea is to allow nonresistant pest individuals to move into the area, breed with the resistant members, and the resistance of future individuals will lessen allowing for more effective control.
As you can surely guess there is more but this pretty much covers the basics.