There is a lot of information already out and if you haven’t take the time, check out the website, www.TheSCNcoalition.com for training and infographics about soybean cyst nematode, you can bookmark this for as you prepare your fields– while on autosteer. Only on autosteer. Our Ohio site, with updated information is also ready www.u.osu.edu/ohscn/. Take your time to see where this pest has been detected, where some of the hot spots are and what we need to be aware of for management. This pest can not be eradicated or removed from a field once it is there, but there is no reason why it should take a lot of our soybean yield, we just need to manage it and that starts with knowing your number.
The first surveys for SCN, early 1990’s, found it sporadically in the state but some populations were very high. In a survey of fields in southern Ohio during the late 2000s, high populations of SCN were found in fields where yields were consistently low. One of the more recent check-off funded projects, identified that more fields than 20 years ago has SCN. Among the 143 fields sampled at a depth of 6 to 8 inches in 51 counties in Ohio, SCN was detected in 81% of the fields and only 6 of the 147 were above the yield damaging levels.
In the current survey, SCN is now at economically damaging levels in approximately 15% of the fields sampled in the current survey. This is a concern.
In addition to more fields planted more frequently to soybean, there are other potential reasons for this increase. SCN has been managed very well for the last 20 years by the deployment of soybean varieties with the PI 88788 source of resistance. However, in Ohio as well as many areas of the Midwest, certain fields have populations that are adapting to this resistance. This resistance is a “slow shift” where the SCN reproduction on the resistant line is greater than 10% compared to a susceptible control cultivar. In fungi, where resistance has developed towards some fungicide this measurement would be 100%, one mutation and the fungus is good to go. In SCN there are several loci and as we now know many copies of the genes, so it is taking longer to adapt but also it is a slow shift where the SCN reproduction of some populations in Ohio and other areas of the Midwest are in the 15, 20, and 30%. Ultimately this means that the resistance can still be used. But for how long, and what fields are we expecting yield loss even with varieties developed from the PI 88788 source of resistance.
In the current survey, we are picking up populations that are adapting to the PI 88788 and Peking sources of resistance.
We are still accepting samples, but we will not process them until later this spring. If you collect samples just hold them in a cool spot in the barn or cellar, out of the light and heat. The survey will end this summer, so while we are practicing social distancing and you need to get out and get some fresh air, take your soil sampler and hit some of those low spots in the fields.