The relatively poorer control from Banvel as a spring dormant treatment is seen again. In several strategies, populations increased markedly after 1987. An explanation could be that we failed to treat plants because they had little if any new growth because they were dormant and thus were missed. 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.