The Potato Volunteer Survival website for estimating potential survival of potato volunteers in Michigan is now available for 2018 risk prediction. Epidemics of potato late blight are initiated from mycelium of Phytophthora infestans. This organism survives between successive growing seasons by overwintering in infected potato tubers intended for seed, or as volunteer tubers that are left in fields at harvest, or within discarded cull and rock piles.
It is difficult to estimate the probability that infected potato stems will emerge from an infected tuber and several factors can influence the fate of the infected tuber, temperature being one of the most important. Over the past five years of monitoring, it has been recorded that over-winter soil thermal conditions have been conducive for the survival of volunteer potatoes, which may act as potential sources of inoculum in the spring.
By clicking on the help page link, you can access additional information about volunteer survival, including the following.
Studies at Michigan State University have shown that tubers of most cultivars appear to break down after exposure to 27 degrees Fahrenheit for about one day. We have developed a model that predicts the likelihood of volunteer survival over the winter based on soil temperatures between Nov. 1 and March 31, summarized below:
|
Hours below 27 F at:
|
Risk
|
|---|
|
2-inch depth
|
4-inch depth
|
|---|
|
> 120
|
> 120
|
Low
|
|
> 120
|
< 120
|
Moderate
|
|
< 120
|
< 120
|
High
|
Conclusion
All regions experienced soil thermal conditions that placed them in the high-risk category for volunteer survival despite the long 2017/18 winter (Figure 1). This situation should alert potato growers to the high risk of potato volunteers surviving the winter. Therefore, all growers should be implementing their integrated pest management (IPM) scouting programs early in 2018 and considering volunteer elimination programs in adjacent crops and non-potato crops if herbicides are registered.
Please visit the MSU Potato Disease website for more information.
This article was published by Michigan State University Extension. For more information, visit http://www.msue.msu.edu. To have a digest of information delivered straight to your email inbox, visit http://www.msue.msu.edu/newsletters. To contact an expert in your area, visit http://expert.msue.msu.edu, or call 888-MSUE4MI (888-678-3464).