With more than a month from planting, UGA Extension Pathologist Dr. Bob Kemerait has some information on nematode thresholds and how we decide to use nematicide and/or resistant variety:
Growers who anticipate a problem with peanut root-knot nematodes and who plan to applpy a nematicide will likely use Telone II or Velum Total. The primary consideration in choosing between a resistant variety, Telone II and Velum Total is the size of the population of nematodes in a field. The economic threshold, that “magic” number that draws the line between when damage from the nematodes is worth treating and when it is not, is 10/100cc soil.
Velum Total (18 fl oz/A) is generally recommended where a grower would have used Temik 15G, 10 lb/A at-plant – which would coincide with “low-to-moderate” nematode populations. Defining “low-to-moderate” populations is unsettling, but I would say anywhere from 10-100 root-knot nematodes per 100cc soil in a FALL-collected sample would be “in the ballpark.” As numbers increase beyond 100/100cc soil, I think a resistant variety or Telone II becomes increasingly important.
Also, given that the root-knot nematodes are generally “clumped” in a field, it is likely that even a field described as “low-to-moderate” will have significant “hot spots” in it. Telone II should be applied in-row at 4.5 gal/A in-row 10-14 days ahead of planting with special awareness of soil conditions during this El Niño season. The possibility of frequent rain events could make fumigation challenging.
An insecticide for management of thrips is still required when Telone is used but not when Velum Total is applied. Velum Total should be applied at 18 fl oz/A for peanuts, and the product can be mixed with other fungicides and inoculants without concern. Whether choosing Telone II or Velum Total, accurate calibration and precise application are critical for maximum success. Growers should ensure that equipment is properly put together and tested for calibration.