Monitoring  

In 1996, the city of Sacramento Department of Neighborhood Services, the Sacramento Tree Foundation, and the University of California received a grant from the California Dept. of Pesticide Regulation to implement an IPM program. Each of the agencies was therefore able to hire extra help to implement our monitoring methods in Sacramento. In addition, the group began to look at the development of new methods for large urban areas as well as to evaluate new and existing control methods (Dahlsten et al., 1998). Previous management for ELB consisted of systemic insecticides applied to all susceptible elms throughout the city on a calendar basis [E].

The first goal of the program was to base treatment decisions on monitoring.

  • The monitoring program began with a small pilot study in 1995 with 4 small sites being monitored at egg peak to determine if treatment was needed.
  • The number of trees managed using the monitoring program grew each year until all susceptible trees were monitored in 1999.
  • City and STEP personnel were trained in the use of the degree-day model and ELB monitoring techniques.
  • All susceptible elms were mapped and apprx. 20% of these were chosen as sub-sample trees.
  • Monitoring has been very successful at reducing the number of trees treated. Between 1995 and 1999 only 11.3% of the trees in the monitoring areas required treatment. By treating only the areas with significant numbers of beetles present, monitoring has drastically reduced chemical use when compared to the previous strategy of treating all susceptible trees (Fig. 4).
  • The damage prediction model successfully predicted damage from ELB in the first and second beetle generations and data from Sacramento fit well in the model (Fig. 5).


[E] Before the monitoring program, all trees were injected with a systemic insecticide on a calendar basis.


Fig. 4 The number of elms treated has declined as more elms were managed under the monitoring program in Sacramento, CA from 1994 through 1999.


Fig. 5 Proportion of samples with egg clusters present vs damage for individual trees, generation 1, 9 years combined. Sacramento data fits well in the previous model.