One drench of the acylalanines CGA-38140 [N-(2,6-dimethylphenyl)-N-(2-furanylcarbonyl)-alanine methyl ester] (72 .mu.g/ml) or CGA-48988 [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-alanine methyl ester] (18 .mu.g/ml) applied 3 days before inoculation controlled Phytophthora root rot of azalea for 24 wk. Rates of 72 and 144 .mu.g/ml of CGA-48988 were phytotoxic to ''Hershey Red'' azalea [Rhododendron obtusum] if applied more frequently than 3 times in 24 wk. Lower rates of CGA-48988 (18 .mu.g/ml) were not phytotoxic. Ethazole (222 .mu.g/ml) was as effective as the acylalanines in control of root rot only if applied at least 4 times in 28 wk. Systemic activity of CGA-48988 was demonstrated 6 days after drenching azaleas at rates 12-36 times the rate that effectively controlled root rot (18 .mu.g/ml). After 5 days, ED50 for linear extension of P. cinnamomi in vitro was 0.11, 0.16 and 0.32 .mu.g/ml for CGA-48988, CGA-38140, and ethazole, respectively. Inhibition of sporangial formation was similar for all 3 compounds with ED50 values ranging 0.11-0.17 .mu.g/ml. The ED50 values for inhibition of chlamydospore formation were 0.01, 0.04 and 1.4 .mu.g/ml for CGA-38140, CGA-48988 and ethazole, respectively. When the compounds were drenched on 6-cm soil columns containing an agar disk of P. cinnamomi at 2 cm, ED50 values for subsequent growth on cornmeal agar were 1.9, 2.2, and 320.0 .mu.g/ml for CGA-48988, CGA-38140 and ethazole, respectively. Ethazole mobility in soil columns was not enhanced by additional water. At the concentration of the acylalanines and ethazole effectively controlling root rot, these materials acted like fungistats rather than fungitoxicants.