Much of the ginseng-production area has received little to no rain over the past month. Combined with average temperatures and lower humidity, this has kept disease pressures, especially Alternaria and Phytophthora, lower than normal except in areas with lingering root disease from last fall. No major insect issues are being reported.
When rainfall is minimal and disease pressures are low, consider extending the spray interval. Most products should last up to 10 to 14 days on a plant in the absence of rainfall (consult the label). If spray coverage is poor, more frequent applications may be necessary to ensure different areas of the canopy have some protection. However, given that most growers travel the same direction in the field with each spray to avoid damaging the older canopies, the same areas of the field are likely to be missed during each spray. It is better and more cost effective to diagnose and fix coverage issues than to apply unnecessarily frequent fungicide application.
Given the dry conditions, the focus of ginseng growers should be on irrigation. It is important to schedule irrigation to ensure you are not applying too much and contributing to leaching of nutrients and increased root disease, while at the same time avoiding periods of moisture stress.
Irrigation Scheduling Using ET Values
The following blog post written for fruit crops provides a good summary of irrigation scheduling based on ET values:
Using ET values to make irrigation decisions: https://onfruit.ca/2021/05/27/using-et-data-to-make-irrigation-decisions/
As part of the calculations, you will need the crop factors (Kc) for ginseng. These are estimated to be 0.3 for seedlings, 0.7 for 2-year gardens, and 0.8 for 3-year or older gardens. Since canopies are full at this time of year, there is no need to adjust these for growth stage.
Irrigation Scheduling Using Monitoring Equipment
Irrigation can be scheduled more efficiently using soil moisture monitoring equipment. For more info, consult this previous post along with the embedded links:
Soil moisture monitoring for ginseng: https://onspecialtycrops.ca/2014/07/23/soil-moisture-monitoring-for-ginseng/
Other Irrigation Articles and Resources
How long do I run my drip irrigation lines?: https://onspecialtycrops.ca/2016/07/08/how-long-do-i-run-my-drip-lines/
Irrigation and seed production in ginseng: https://onspecialtycrops.ca/2012/06/14/irrigation-and-seed-production-in-ginseng/
OMAFRA – General Irrigation Resources: http://omafra.gov.on.ca/english/engineer/irrigation.htm