The approach is successful because it is unlikely that a virus will have traits to protect it from all three forms of attack. The combination approach, at about U.S. $18,000 per year per HIV patient, is standard treatment in the United States.
"Using anything other than the full arsenal of weapons is very dangerous and ultimately very expensive," says Palumbi.
The overkill strategy is also relevant when dealing with agricultural pests. Rather than relying on chemicals alone to destroy unwanted plants or bugs, farmers should attempt to physically control the populations of these species. For weeds this means removing resistant individuals by hand.
Using a range of herbicides is also another way to slow the appearance of resistant species. A genetic variation that enables a weed to survive an herbicide during one season is unlikely to protect it the following year from a different chemical that kills through another mode of action.
To slow the evolution of resistant bugs also requires alternating insecticides. Additionally, Palumbi recommends planting some crop varieties that contain toxin-producing genes and some that do not. This crop diversification creates a varied environment in which both resistant and non-resistant insects can thrive; this prevents only resistant bugs from engulfing the population.
None of these approaches are anything but common sense, provided you accept that evolution is happening continuously, says Palumbi.
The bottom line: Evolutionary trajectories of unwanted species should be included when analyzing the use of new drugs and chemicals.
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