EVALUATION OF MALTOL FOR CONTROLLING WESTERN GALL RUST OF LODGEPOLE PINE

Maltol (3-hydroxy-2-methyl-4H-pyran-4-one) occurs in conifers, is prod uced by the rust hyperparasite Scytalidium uredinicola, is used as a f ood additive, and has been suggested for use in pharmaceuticals. Lodge pole pine (Pinus contorta var. latifolia) seedlings were treated with 5 mL of maltol at 0.0, 1.6, 3.2, 4.8, 6.4, and 8.0 mg/mL, as a soil dr ench prior to inoculation with western gall rust (Endocronartium harkn essii). The protective effect of maltol treatment was proportional to concentration; the highest dose reduced infection by 56.3%. Seedlings were drenched with 5 mL of maltol at 8.0 mg/mL and inoculated 2, 9, 16 , and 30 days later. Infection on seedlings inoculated within 2 days w as reduced by 48%. The protective effect declined with time since trea tment and was positively correlated with the maltol concentration in t he seedlings. Infection was reduced by 28% under field conditions. It thus appears that maltol has some potential as a practical control for western gall rust on lodgepole pine seedlings.