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.
One of the most economically damaging insect pests of sunflower in South Dakota is the red sunflower seed weevil. Although the National Agricultural Statistics Service (USDA) reports that only 23% of sunflowers in South Dakota are blooming, it is important to scout fields for the red sunflower seed weevil. Last week, we observed adults of this pest on non-flowering sunflower near Onida and Highmore.
It is getting close to that time of year again when sunflower growers should be scouting sunflowers for insect pests that directly affect the head and developing seeds. One of the more important pests to scout for is the banded sunflower moth due to its potential to reduce yields.
During sunflower scouting last week, there were several sunflower plants that had defoliated leaves with webbing present. The insect causing this defoliation was the thistle caterpillar, which is the immature stage of the Painted Lady butterfly.
The pea leaf weevil was introduced into the United States in the 1920’s on both the East and West coast. Although not yet reported in South Dakota, the pea leaf weevil is getting closer. In 2016, researchers at North Dakota State University documented fields that had pea leaf weevil infestations.
While checking on my garden this week I noticed that some heavily defoliated plants including green peppers, radishes, okra, and green beans. I was expecting to find large grasshopper populations present due to the jagged appearance of the holes left in the leaves.