Controlling Aphelenchoides subtenuis nematodes with a hot water treatment in Crocus and Allium

Several bulbous crops like Crocus, Allium and some species of Tulipa and Narcissus can be infected with the nematode Aphelenchoides subtenuis. The nematodes cause retarded growth, poor or no flowering and eventually death of the bulbs and corms. A hot water treatment after lifting the bulbs has proved to be effective in controlling the nematodes. Due to a high incidence of infected stocks of bulbs a study was conducted to establish if the efficacy of the treatment could be improved by altering the timing and the temperature of the hot water treatment and the storage temperature of the bulbs prior to the hot water treatment. Bulbs and corms of Allium and Crocus were given a hot water treatment of four hours at 43.5 or 45°C. Between lifting and the hot water treatment the bulbs were stored at 25 or 30°C. Prior to the hot water treatment some of the bulbs were immersed in water for 24 hours. The hot water treatment was performed at 7, 10, 12 or 14 days after lifting the bulbs or corms. Controlling Aphelenchoides subtenuis was only effective when the hot water treatment of four hours at 45°C was applied within 10 to 14 days after lifting the bulbs. When Crocus was stored at 30°C a hot water treatment was only effective until 10 days after lifting. When stored at 25°C a treatment was effective until 14 days after lifting. The hot water treatment became more effective when the bulbs were immersed in water for 24 hours prior to the hot water treatment.