Pacific flatheaded borer may be controlled on established deciduous fruit and nut trees with a preventive dieldrin spray when the application is made before eggs are deposited in the spring. However, this treatment is an expensive substitute for good cultural practices to keep the trees in healthy vigor and free from sunburn.

Assistance with plot work was obtained from the following farm advisors: D. H. Chaney, C. A. Ferris, M. H. Gerdts, L. Hendricks, D. M. Irving, L. B. McNelly, G. R. Post, D. E. Ramos, A. H. Retan, and R. R. Sanborn. Aid in plot designs and statistical analysis was obtained from G. R. Rowe, Extension Economist, U. C., Berkeley.