This fall numerous volunteers from private industry and SDSU Extension will hit sunflower fields across South Dakota to participate in the biannual sunflower survey. Every other year volunteers survey one field out of every 10,000 acres of sunflowers being grown in every sunflower producing state and some Canadian provinces.
While scouting sunflower for insects that may cause yield loss, you might spot some small red and gray beetles that are present on the head or close to it. These two insects are the red sunflower seed weevil and the gray sunflower seed weevil.
With growers’ interest emerging, SDSU Extension and research faculty teamed up and initiated a study in 2016 in Northeast SD to evaluate the effects of plant growth regulator. The study was conducted at the SDSU Northeast Research Farm (NERF) near South Shore, SD.
Alternaria leaf spot and powdery mildew were found at low levels in sunflower scouted in east and central South Dakota, in addition to the sunflower rust and Phomopsis stem canker reported last week.
Sunflower is at the growth stage (usually at or after blooming) when most foliar diseases start to develop. Areas of the state that have received frequent rains may begin to see a few diseases including Phomopsis stem canker and sunflower rust.
A couple of weeks ago, we covered red sunflower seed weevil scouting. Last week, we received calls regarding this pest and the population reports were staggering. The recommended threshold for the red sunflower seed weevil is 4-6 adult weevils per head.
One cover crop that has caught attention and has consistently worked in South Dakota environments where pre-dominant rotation is corn-soybean is winter rye. Winter rye is known for its winter hardiness allowing late fall planting and puts on a rapid growth the following spring.
One of the insects that needs to be scouted for after the inflorescences begin to open (R4) through head maturity is the sunflower moth. Sunflower heads are most susceptible to damage caused by sunflower moth caterpillars from the onset of anthesis (R5.1) to when the petals begin drying (R6).
For the last two years, we have been observing large populations of Dectes stem borer in South Dakota sunflowers. This spring, we noticed large numbers of the adults on volunteer sunflowers in field edges.
Interest in using cover crops after small grain is increasing in South Dakota. Cover crops provide diversity into the cropping system, reduce soil erosion, increase soil biological activity, and also help recycle nutrients in the soil.