We are starting to get reports of soybean aphid populations that are exceeding the economic threshold of 250 soybean aphids per plant in parts of South Dakota. So far, the areas where spraying for aphids is occurring are located in the northern counties, but we are also observing populations that are near threshold near Brookings and Volga.
What are the odds that a soybean plant can be killed by lightning? Very low! In a recent ten year period, Eastern South Dakota had an average of one to two strikes per square kilometer, per year. While quite uncommon for lightning to damage row crops, it does happen. Thunderstorms can have lightning that can burn soybeans plants leading to their death.
Soybeans in South Dakota are in their moisture-critical reproductive stage. Drought stress during this growth stage can significantly impact yield, so here are some things to look for. When soybean is drought stressed, the leaves will flip over to show their silvery-green undersides. This is a defensive mechanism they use to reflect more light, reducing the amount of sunlight the plant takes in through its leaves.
We are still observing small populations of soybean aphids throughout much of Eastern South Dakota. In the fields, these populations are appearing as “hot spots”, where a single plant may have as many as 200 to 300 soybean aphids on its leaves and stems.
In June, we discussed how we were observing quite a few bean leaf beetles in the Southeast Region of the state. Now, as we enter August, we are again observing an uptick in bean leaf beetle numbers.
What does dicamba off-target movement do to soybeans that are not genetically tolerant to the herbicide? This question has been raised many times over the past month in South Dakota as more dicamba is being applied to fields with the introduction of dicamba-tolerant soybeans to the market.
The 2017 IPM Field School was at the Southeast Research Farm during the third week of July. One of the sessions that attendees participated in was “Insect Management: Techniques for Scouting and Identification of Insect Pests.”
Bacterial blight was found in several soybean fields scouted in Brookings, Deuel and Moody counties. Recent heavy storms and/or hail injury may have increase the prevalence of bacterial blight. As the weather heats back up, typically over the optimum 75 degrees, the growth of this bacterium will be stalled.
We have been observing and receiving numerous reports about redheaded flea beetles in soybean throughout South Dakota. These beetles get their name due to the distinct red-brown colored head, which is contrasted by their otherwise shiny black bodies.
Throughout South Dakota we are beginning to notice a lot of small green caterpillars in soybean fields. Currently, these caterpillars aren’t causing too much defoliation due to their small size, but as they grow their feeding may become more noticeable.