Optimizing Nematode Control Timing and Irrigation Methods for Exported Garden Tree Seedlings.

When exporting garden tree seedlings overseas, plant-parasitic nematode removal through root washing and chemical treatment (hereafter, referred to as nematode control) is imperative. This study focused on Camellia sasanqua, Ilex crenata, and Pinus thunbergii, examining the impact of irrigation methods and mist intervals on their quality during nematode control in September, when it is considered highly effective for plant-parasitic nematode management. We aimed to identify the optimal irrigation method for garden tree seedlings. If nematode control in September significantly reduces the number of exportable individuals, alternative control periods must be considered, regardless of the September period’s efficacy against plant-parasitic nematodes. Therefore, we investigated quality deterioration occurrences during nematode control in April, August, October, and December, determining the optimal period for nematode control in garden tree seedlings. The results showed that during September control, both hand irrigation and mist irrigation were suitable for C. sasanqua and I. crenata, whereas hand irrigation alone was suitable for P. thunbergii. Considering the peak effectiveness of nematode control during their breeding season from September to October, the optimal control period was September–October for C. sasanqua, October for I. crenata when quality decline was less likely to occur, and September–October for P. thunbergii, despite a 20%–30% quality decline.