Specialty Crop Report – Ginseng Edition

Crop Update
Rhizopus – A Disease of Wet Soils
New Crops Workshop

Crop Update
Many ginseng areas have received heavy rains over the past week. Phytophthora, Cylindrocarpon and Pythium are the main diseases showing up in ginseng gardens at this time. Under these wet conditions, Phytophthora root rot can spread rapidly from plant to plant. It is very important to maintain protection of the crop from Phytophthora through a rotation of Aliette and Maestro. Botrytis is also present on senescing tissues. While Botrytis pressure has not been high in many gardens, pay close attention to your gardens and apply Elevate once the disease begins to increase. Alternaria levels have been low so far this year. However, it is important to continue to protect the crop against all foliar diseases. Continue to monitor gardens closely for all foliar and root diseases. 

After heavy rains, it is a good time to monitor new gardens for areas where water pools. Drainage should be improved in these areas before the new ginseng crop is seeded. Also watch for ponding in trenches of existing gardens and consider subsoiling or adding bark chips or straw to these trenches to avoid splashing when machinery or field workers move through the garden. 

Rhizopus – A Disease of Wet Soils
With the very wet weather in some areas, Rhizopus may begin to show up in ginseng gardens. Rhizopus is a common soil fungus. It is also commonly found in the air and you may have seen it as a bread mould. It would appear as a fluffy white growth with tiny black dots. The dots are spore cases and they release tiny spores that disseminate on air currents. It is not a serious problem on ginseng every year, but because it is present in the soil, it can invade damaged roots when conditions are right. In wet gardens, it can cause a mushy rot of the lower stem on older roots and a stem and crown rot of seedlings. It does not usually move from the lower stem to the crown on older roots unless conditions are wet and warm and the crown is damaged by another disease. It can easily be mistaken for Pythium. On older roots it can infect roots that are already infected with Cylindrocarpon and the resulting rot causes the root to become a white gooey mass covered with soil. The only way to control Rhizopus in the field is to reduce soil water by proper site location and drainage and to reduce damage to roots by other diseases. 

Rhizopus can also be a problem in the kilns. Rhizopus can remain alive on roots through the cooling, washing and drying procedures. It is usually present in soil that clings to the roots or can be present in the kiln itself if it was not properly disinfected. Rhizopus usually develops slowly until it is placed in the kiln. If the air is very humid in the kiln at the start of drying, the fungus can develop rapidly. Infected roots, once they are dried, exhibit grey patches (Figure 1) with a slight blistering. When sliced, these roots will have a dark or grey discolouration and dark rings inside (Figure 2). They will also have an off taste and smell. To avoid Rhizopus damage to roots in the kiln, ensure that dryers are properly disinfected. Also, avoid overfilling kilns because humidity will remain high for a longer period of time, and this will allow a longer window for Rhizopus to develop on the roots. 

Figure 1. A dried root with extreme darkening due to Rhizopus infection in the kiln.

Figure 2. Moderate damage from Rhizopus after drying. Note the darkened interior in spite of little darkening at the surface. 

New Crops Workshop

New Crops, Old Challenges:
Non-traditional crops integrated crop management workshop

Come out to the Simcoe Research Station to learn about:

-          Non-traditional and specialty crops: demonstration plots of example crops
-          Pest management and sprayer technology: discuss with provincial specialists
-          Cover crops: opportunities to save your nitrogen dollars 
-          Current nitrogen research conducted by the University of Guelph
-          Enjoy refreshments, meet with other producers and take the opportunity talk
            with University of Guelph staff and OMAFRA specialists

Date: Tuesday August 18, 2009
(Rain Date: Thursday August 20, 2009)
Time: 1:30 p.m.-5:00 p.m.
Place: Simcoe Research Station

PLEASE RSVP BY AUG. 14 BY CALLING 519-426-7127 ext. 323

Questions about ginseng can be directed to Sean Westerveld, OMAFRA’s Ginseng and Medicinal Herbs Specialist at 519-426-4323; E-mail: sean.westerveld@ontario.ca.