Monthly Archives: March 2016

March 11, 2016 · 2:03 AM

Peanut Nematode Control Update

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.

Ambrosia Beetles: First Flight Reported

Ambrosia beetle toothpicks

UGA Extension Pecan Entomologist Dr. Will Hudson confirmed the first ambrosia beetle flight reported yesterday in southern Grady County. ABB initial flight usually occurs when temperatures go over 70 degrees. A few days ago, Dr. Hudson said they will likely fly this week. Growers with young pecan trees, especially under 5 years, need to check their traps. Remember, we are looking for the “toothpicks” on the wood. This is the frass from the beetles as they bore into the tree.

Once we see AAB attacking the traps, we need to spray. Trunks of young trees should be sprayed with a pyrethroid. Barrier sprays of Lorsban will not work for AAB. The beetles are particularly attracted to stressed trees (although they will attack non-stressed trees.) Pay close attention to trees planted in poorly drained soil. Once a flight is observed with the traps, it is advisable to spray each week in problem areas until the trees have leafed out.

Dr. Hudson speaks at 2016 Thomas County Pecan Update in Thomasville

Smutgrass

Seedhead

Smutgrass is a non-native, perennial grass that can be a real issue in our pastures and one where management can be difficult. These pics I took a month ago. The seed head is a long spikelike. Leaves are usually folded but can be flat. They are also smooth. Many times the seadhead or spikelet is infected with black smut.

Ccows will graze the smutgrass for some time then they will stop. When the pastures become infested, large areas of the pasture are not grazed.

Control

In terms of chemical control, hexazinone (Velpar, Velossa), is our main option for smutgrass. One issue is injury to Bermuda. Hexazinone will injure bermuda pretty good and can eliminate the first hay cutting. Bahia and Bermuda will recover from temporary burn and yellowing within two to four weeks of application. We need to target smutgrass around between April and July, when humidity is high and air temperatures are over 80 degrees. Hexazinone is root absorbed and requires about one-half inch of rainfall within two weeks of application. Fall applications are not very effective.

Another point to remember is we need to use low rates on coarse, sandy soils and high rates on clay soils. Hexazinone can injure trees (especially oaks). Caution should be used near desirable deciduous trees.

For additional information, visit Smutgrass Control in Perennial Grass Pastures.