Black Oats for RKN Management

Nathan Kleczewski, Extension Specialist – Plant Pathology;; @Delmarplantdoc

Last season we had some questions about the use of black oats for managing root knot nematode (RKN) in various crops. Black oats are purported to be a poor host for RKN, and some growers were interested in knowing if they had any potential value here as a cover crop. Last fall, we conducted a small microplot study in Newark where we installed several 3-gallon pots into the ground, and filled these pots with field soil that was free of RKN. We then placed a single tomato plant infested with RKN into the center of each plot, and allowed the plants to grow until September of 2016. The plants were cut at the soil line and worked into the soil. We then either left the soil fallow, or sowed black oats or barley into microplots at recommended rates, with each treatment replicated six times. The plots were fertilized following UD Extension guidelines. In the spring, the plants were mowed and a single cucumber plant planted into the center of each plot in late May, 2017. The plants were allowed to grow for 2 months, were removed from microplots, and were rated for RKN galling. The scale used was a 0-5 scale where a 0 was free of RKN and a 5 was completely galled. The results of the trial are below. As you can see, we saw that black oats reduced RKN galling somewhat, but that barley slightly increased galling. We also noted that the overall stand and heartiness of the black oats was not overly impressive, even though we had a moderate winter and spring. Black oats do not tolerate freezing temperatures well. Consequently, although this trial provides some indication that black oats may provide some benefit for reducing RKN, other factors, in particular cost and winter hardiness, are likely to prohibit its use in Delaware.

RKN gall ratings on cucumbers planted in microplots previously planted to barley, black oats, or fallow. Different letters indicate significant differences using Fisher’s LSD (0.05). 0= free of galling 5 = completely galled.