Soybean Aphids Surface

Start Scouting For Soybean Aphids

From the University of Nebraska

 

The first soybean aphids of the season were found on July 3 in Dixon County, NE near Concord. Aphids are generally found in late June to early July in Nebraska, so this is not unexpected. The infestation was very small and lady beetles were already feeding on them; however, current weather conditions are favorable for aphid survival and reproduction, so they bear watching. In any case, if you have not begun scouting soybeans for soybean aphids, now is the time to begin.

The aphid is light green to pale yellow, less than 1/16 in. long, and has two black-tipped cornicles (cornicles look like tailpipes) on the rear of the abdomen. It has piercing-sucking mouthparts and typically feeds on new tissue near the top of soybean plants on the undersides of leaves. Later in the season the aphids can be found on all parts of the plant. It is the only aphid in North America that forms colonies on soybean.

Soybean aphid populations can grow to extremely high levels under favorable environmental conditions. Reproduction and development is fastest when temperatures are in the 70s through the mid 80’s. The aphids do not appear to do well when temperatures are in the 90s, and are reported to begin dieing when temperatures reach 95 degrees. When populations reach high levels during the summer, winged females are produced that migrate to other soybean fields. Like a number of other insect species (e.g. potato leafhoppers), these migrants can be caught up in weather patterns, moved great distances, and end up infesting fields far from their origin. These summer migrants were most likely the major source of infestations in Nebraska during the last couple of years.

Soybean aphids injure soybeans by removing plant sap with their needle-like mouthparts. Symptoms of soybeans infested by soybean aphids may include yellowed, distorted leaves and stunted plants. A charcoal-colored residue also may be present on the plants. This is sooty mold that grows on the honeydew that aphids excrete. Honeydew in itself makes leaves appear shiny. Soybean plants are most vulnerable to aphid injury during the early reproductive stages.

In much of the soybean aphid’s range, significant aphid infestation has often occurred in the early vegetative stages. These infestations then undergo rapid population growth to reach high populations during the flowering stages (R1, R2). In Nebraska aphid populations can reach economically damaging populations in late July, but most reach economically damaging populations in August, when soybeans are in the mid-reproductive stages (R4-R5). During 2004 there were many fields where aphid populations peaked in late R5 (beginning seed) to early R6 (full seed)

Efficient spraying- more for your money

Applying efficiency to your spraying routine
By Shelby Haag

When is comes to spraying, the chemical is only as effective as the application process itself. With a better knowledge of equipment and product, producers can increase spraying efficiency.

Robert Klein, University of Nebraska- Lincoln extension cropping systems specialist, has been offering producers advice through workshops, which include more than simply sprayer calibration. “Calibration is very important, but before we start spraying we take a pressure gage and check the pressure on the boom,” Klein said. “This is critical because often it’s found that there is not even pressure throughout the boom. If the pressure is not even across the boom, calibration is a waste of time.” Klein also recommends checking the pressure gage in the cab to determine if there is a difference, either high or lower in the boom.

Calibration of sprayers includes speed, spacing and nozzle flow rate. Robert Wolf, K-State extension application technology specialist, stresses the importance of setting up a sprayer properly. “Producers need to be actually putting out the amount of chemical that they think they are in order to get effective coverage,” Wolf said. “A lot of times a farmer or commercial applicator is going through the field and paying attention to the rate controller and may not have a good feel for what’s going on in the droplet situation.”

Spray nozzle tip selection is a topic producers should become familiar with. “It’s important to know where various nozzles should be used and what pressure it should be used with,” Klein said. “Different nozzle materials offer different advantages – brass, plastic, stainless steel – you really have to know what your purpose is and what type of droplets are desired.”

A concern is that the nozzles are not putting out the correct amount, or that there is a pattern problem and coverage might not happen as accurately as it should, Wolf said. That’s really a critical issue when you’re trying to get coverage on the targeted surface. “Some producers in Kansas are operating on the edge with low volume of application, and with lower volume of application the more risk you have because it’s smaller droplets and less material being put out,” Wolf said. “If it’s a hot, dry windy day the coverage lessens, and that is something to keep in mind.”

Wolf said it’s important to get the sprayer set up to deliver the right size of droplets. “Applicators are getting more and more focused on that because we are learning that certain types of weed targets are going to require different kinds of coverage and droplet size aspects than others, and the sprayer must be set up for it,” Wolf said. “That is going to require applicators to have a pretty good knowledge on the type of nozzle they are using.”

Klein and Wolf both exhibit a nozzle demonstration at their various spraying workshops and seminars. By using a spray table and strobe light to show the various particle sizes and nozzle types, producers are able to see side-by-side the advantages and disadvantages of each nozzle. “We try to illustrate what the different nozzle technologies will do through our demonstrations,” Klein said. “It gives the operator a visual picture of how the nozzle will perform and after seeing the difference producers understand why it’s so important.”

Chemical companies are starting to do more research to identify what droplet sizes might be in order for farmers to better set-up the sprayers, Wolf said. Also, nozzle manufactures are providing data to the farmers, that information can be used to select the right nozzle for the job. “Chemical labels are also starting to address the droplet size issue,” Wolf said. “The American Society of Agricultural and Biological Engineers has adopted a standard which the EPA is promoting and chemical companies are starting to use. That standard specifies a droplet size spectrum broken down into six categories; very fine, fine, medium, coarse, very coarse and extra coarse.”

Other technologies such as auto-steer and boom control provide opportunity for more efficient application. “Boom height control can be used to maintain a uniform height across the field,” Wolf said. “Boom swath control with GPS and a rate controller system keeps track of areas that are sprayed and not sprayed. The boom will turn on and off in segments so that applicators don’t double spray or miss spots.”

Wolf has noticed that more farmers in the Midwest are doing their own spraying than in previous years. “With the technology changing everyday and the newer nozzles it’s very important that we have the various programs through extension service to get information to applicators,” Wolf said. “From my experience producers are very interested in learning more about the topic, they will come to the meetings and ask good questions – this education something that’s needed.”