Low falling numbers, which have struck distinct regions of Eastern Washington periodically, have shown up once again in the 2016 crop. This season’s outbreak is widespread, but on a random basis. Low falling numbers can be caused by two factors: rain at harvest and Late Maturity Alpha Amylase (LMA) activity. This year, LMA is the primary factor causing low falling numbers.
Falling Numbers under 300 could result in a crop insurance claim. Since the 2011 crop year, the Risk Management Agency implemented a Falling Numbers Discount Factor Table as an allowable quality adjustment for crop insurance. If you are experiencing low falling numbers, it is important to consult your crop insurance agent.
Late Maturity Alpha Amylase develops in susceptible germplasm when a temperature shock occurs to the wheat during grain filling. The shock may be from warm to cold or cold to warm, but usually with a significant variance of hot days and very cool nights. This phenomenon kicks on the chemical process leading to starch breakdown without any rain falling on the crop.
Most overseas customers specify a minimum falling number score in their tenders. For soft white, club and hard red winter, that score is 300. For hard red spring it is 330. End users have found scores lower than that can affect the quality of their products. Some customers, such as Egypt and Bangladesh have lower falling number specifications, but with the rise of the Black Sea wheat producers, sales into those markets occur less frequently.
The falling number test was developed in 1960s and has been accepted worldwide since the 1980s. Major buyers have been using the test since 1997. It is difficult to blend for falling numbers, making the job of the elevator industry especially troublesome.
Funded by the Washington Grain Commission (WGC), Camille Steber, a scientist with the Agricultural Research Service of the U.S. Department of Agriculture in Pullman, has been investigating the connection between varieties and falling numbers for the past three years. At the direction of the WGC, she undertook to test all varieties by location to understand their susceptibility to LMA. Her research has been published in Wheat Life, and she has a website which provides falling number scores for varieties at 20 Eastern Washington research locations. Past Wheat Life issues are available here. Camille’s Timely Topic about the falling number issue can be found here.
Mike Pumphrey, spring wheat breeder at Washington State University, said almost all of the falling numbers problems reported until now have been activated by LMA. Rain, under the right conditions, can reduce falling number scores even more, but Pumphrey’s convinced that’s not the primary problem this year.
Rich Koenig, director of extension at WSU, has convened a team of researchers to go beyond the research that has already proven the connection between varieties and LMA. With the help of the Western Wheat Quality Lab, the new goal is to create a listing of varieties, site by site, that are susceptible to low falling numbers and should not be planted. The WGC has also asked WSU to step up their analysis of new varieties that have not been included in previous data.
Pumphrey said there are plans to include that information in a seed buyers or quality publication, much as stripe rust levels of resistance are published now. He said there is also an effort to investigate the weather connection by accessing information compiled by the university’s Ag Weather Net stations, with the onset of the LMA phenomenon.
Ordinarily, wheat plants are most susceptible to LMA 25 to 30 days after flowering. But this year, there was an extra few weeks of grain fill. Pumphrey said that’s unusual and very difficult to factor into the effect on falling numbers.