PULLMAN, Wash. — First COVID-19 then DROUGHT-21. We just can’t seem to catch a break. As I drive around the region, I see a lot of green fields, but that green often turns out to be common lambsquarters or prickly lettuce rather than chickpeas or lentils. The very dry spring resulted in poor or no activation of soil-applied herbicides. Combined with poor stands and stressed crop plants, weeds have thrived in portions of many pulse crop fields in Eastern Washington.
Additionally, uneven maturation of pulses across the field is quite common. Areas with poor stand often are greener than areas that had good stand establishment that resulted in greater competition for soil water. Likewise, plants in wetter areas of the field are greener than plants in drier portions of the field. Taken together, uneven ripening and plentiful green weeds makes the need for harvest aid herbicide applications highly likely this year.
There are several products labeled for use as a harvest aid in chickpea, dry pea, and lentil (see the 2021 PNW Weed Management Handbook for details). These include carfentrazone (Aim EC), flumioxazin (Valor EZ), glyphosate (many trade names), paraquat (Gramoxone SL 2.0), and saflufenacil (Sharpen). Do not use saflufenacil as a harvest aid in green lentil varieties or glyphosate in dry peas grown for feed. Except for glyphosate, these products provide rapid desiccation of the crop and weeds. Glyphosate may require up to 14 days to adequately desiccate weeds and crop plants.
Preharvest intervals range from 0 days for carfentrazone to 7 days for glyphosate and paraquat. Minimum carrier volumes for ground application range from 10 gallons per acre for carfentrazone and saflufenacil to 20 gallons per acre for gramoxone. Desiccation is improved with increased carrier volumes because it increases plant coverage, which is particularly important for non-translocated herbicides. Glyphosate is the only translocated herbicide labeled for harvest aid in pulse crops.
Harvest aid treatments should be applied when at least 80% of seed pods are yellow to brown and less than 30% of the leaves are green. Be sure to read the product label before making a harvest aid treatment. Consider treating only the portions of the field where desiccation is needed. Before applying a harvest aid treatment, check with the potential buyers to make sure they will purchase a crop treated with the herbicide you will be using. Some pulse crop buyers will not purchase crops treated with glyphosate.
— Drew Lyon for Timely Topic, WSU
For more Washington news, click here.