If this were true, we should have seen similar population increases for Spike because it too was applied when bushes were dormant. Perhaps the same bushes were treated with Banvel from year to year as the control ratings were lower than for other treatments. Most strategies show a rapid and continual decline in percentage of bushes remaining. This suggests that after 3 yr of effective control, treatment frequency can be reduced to a maintenance program. The cost of each strategy is a function of product price and number of bushes treated.
Any economic evaluation is based on certain assumptions.
Our included the following. For simplicity, we used estimated prices for 1992. This has probably overestimated the cost somewhat. We assumed 100 ml of solution were used per bush. We actually applied and average of 60 ml but believe that producers and others would tend to apply more than we did.