1. The authors are in the Department of Nematology (E.P.C.-C., J.C., E.E.L., and S.A.N.) and the Department of Entomology (E.E.L. and J.R.C.) at the University of California, Davis, CA 95616, USA; the Department of Plant Pathology (G.W.D.) at the University of California, Riverside, CA 92521, USA; and the Center for the Economics and Demography of Aging at the University of California, Berkeley, CA 94720, USA (J.R.C.).(E.P.C.-C.)