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.
While scouting alfalfa this week we observed a field that had pea aphids at population densities that greatly exceeded the economic threshold of 400 pea aphids per 30 sweeps in alfalfa that is taller than 10”. The populations were so extreme that in 30 sweeps we were collecting approximately 1,000-3,000 pea aphids.
While scouting pea fields last week, we noticed some populations of tarnished plant bugs. Although these insects are rarely an issue in most crops, they can cause considerable damage to field peas due to pod feeding.
Following the first cutting, alfalfa fields should be monitored for the presence of blister beetles. These beetles are usually considered beneficial insects. However, blister beetles can become an issue when large populations of them are present in alfalfa fields.
During the SDSU Extension Field Pea & Lentil Tours in the Harrold and Fort Thompson areas last week, small populations of pea aphids were observed in each of the fields. The aphid populations were well below the recommended thresholds and shouldn’t be much of a concern at this time.
SDSU Extension will be hosting a tour of the Small Grain Crop Performance Trials located near Selby, SD. The tour is set for July 6, 2017 at 5:00pm (CST). Attendees will have the opportunity to view field peas, winter and spring wheat, and oats varieties to see how they perform in the field.
We are finding large numbers of alfalfa plant bugs showing up in alfalfa fields throughout South Dakota. By directly feeding on alfalfa plants, alfalfa plant bugs can become an issue for seed production as well as forage quality.