Weed control is always an issue with peanuts because it doesn’t compete aggressively with several common weed species in the Southeast. Delayed planting can put weed control out-of-synch with spraying for other crops and create some problems in keeping peanuts clean from planting to digging.

Recent research in Virginia indicates yield losses to horsenettle can range from 15-20 percent. Losses to this particular weed may become even more important to peanut growers because horsenettle has shown resistance to a wide range of herbicides, including glyphosate.

Lack of moisture in some areas of the V-C Belt created problems with activation of pre-plant herbicides used to replace glyphosate and to help manage horsenettle.

Common lambsquarters has likewise shown some resistance to glyphosate, especially in the northern third of the Carolina-Virginia peanut belt. Losses of up to 40 percent in heavily infested and poorly managed fields have been documented.

Despite the publicity over the loss of yield to pigweed, the potential risk to this commonly occurring weed in peanuts is less than half that of cocklebur. It was managed routinely as a side benefit to using a wide range of herbicides that go back to the days of using Dyanap and a wide range of so called ‘yellow herbicides.’

While cocklebur is much easier to manage than pigweed, it can be devastating in fields in which it is allowed to compete with peanuts for moisture and nutrition.

Generally, keeping peanuts weed free for 6-10 weeks after planting significantly lowers the risk of yield loss to weeds. However, planting later than recommended, certainly past the first week or two of June puts growers at a heightened risk for all weeds.

Late planted peanuts have the extra risk of competing with weeds in hotter, dryer conditions than May-planted peanuts.

Not only does yield loss occur from competition with weeds, but late-occurring weeds commonly interfere with digging. Harvest time losses in yield and in peanut quality can combine to create significant economic losses with late planted peanuts.

Heat and drought throughout most parts of the Carolina-Virginia belt in July will likely intensify problems growers will have with late planted peanuts at harvest time.

Despite the long planting season and ongoing mid-season problems with heat and drought, peanuts planted on time appear to be on course for an average to good yield and quality year.

rroberson@farmpress.com