The heavy rains over the past few days have resulted in standing water in many gardens. This will increase the risk of Phytophthora root rot as swimming spores (zoospores) move through the water to new plants. The biggest risk with standing water is the potential for splashing of the spores in the water onto leaves, which would lead to a foliar infection. Foliar infections lead to airborne spores that can travel great distances on wind currents and lead to infections in new areas of the garden, neighbouring gardens, or many kilometres down the road. Growers should take the opportunity after heavy rains to identify drainage issues and correct them before the next heavy rain. This is especially true for new gardens that have not been seeded yet. It is much easier to correct issues before the garden is in place than to wait until the seedling year.
Alternaria is still an issue in many gardens. Lack of Alternaria control is usually either a timing or a coverage issue. There are numerous effective products for Alternaria control, and assuming they are used at the right rate, according to the label directions and with good rotation of active ingredients, they should provide protection if the pathogen comes in contact with treated surface. However, sometimes the timing of application is out of the growers control if heavy rains interfere with spraying and wash some of the protection off of the leaves.
There are isolated plants in some gardens starting to turn colour as they would normally do in the fall. This is most likely due to root disease, primarily Cylindrocarpon, or another root disease that limits the uptake of water and nutrients. Plants turning colour at this stage should be dug up and the disease diagnosed so appropriate treatments can be applied to prevent further spread.
There have not been many reports of other issues affecting ginseng over the past few weeks. Damage from root lesion nematode is often reported, but appears to be mainly a result of feeding in the seedling year. This damage is often not identified until subsequent years when the crop is stunted.