Refinement of Hot Water Treatment for Management of Aphelenchoides fragariae in Strawberry.

The effects of hot water treatments on a California population of the foliar nematode, Aphelenchoides fragariae, and on five strawberry cuttivars ('Chandler', 'Douglas', 'Fern', 'Pajaro', and 'Selva') were assessed in laboratory and greenhouse tests. Nematodes extracted from fern leaves were placed in water maintained at 44.4, 46.1,47.7, or 49.4 C for different time periods. Exposure periods of 15, 5, 4, and 2 minutes were required to produce 100% mortality at 44.4, 46.1, 47.7, and 49.4 C, respectively. In a water bath, 4 minutes were required for strawberry crowns initially at 25 C to equilibrate with temperatures ranging from 44.4-54.4 C. The maximum exposure periods that did not significantly reduce subsequent plant growth and flowering were 30, 15, and 10 minutes, at 44.4, 46.1, and 47.7 C, respectively. Survival of Selva was lower (P = 0.05) than for the other cultivars. Treatment at 49.4 C for 5 minutes significantly reduced plant growth and flowering of all cultivars. The minimum-maximum exposure periods that killed A. fragariae without damaging the cultivars tested were 20-30 minutes at 44.4 C, 10-15 at 46.1 C, or 8-10 at 47.7 C.