By Christina DiFonzo... Soybean aphid flights have occurred over the last several weeks. We have also had storm fronts that may have carried soybean aphid greater distances and dropped winged aphids on bean fields. Once a winged aphid finds a soybean field, it moves from plant to plant, depositing several babies each place it stops.

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Christina DiFonzo...You all know I love aphids, and that I can talk endlessly about them. But I really wasn’t kidding the last few weeks when I reminded you to watch fields for my favorite pest. Populations per plant in most of my field plots remained low throughout July, but the percent of infested plants was high, and has increased steadily - nearly 100 percent in some trials last week.

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Christina DiFonzo...Soybean aphids are present, but in low numbers. Last week’s big rain and hail event that hit central and southern Michigan was probably heavy enough to wash aphids off of plants, but in general moderate rains do not remove aphids from plants.

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The Pesticide Application Technology for Soybean Rust and Soybean Aphids is a factsheet put together by the Michigan State University Extension. The factsheet covers the application of peticides to soybean rust and soybean aphids; including management and sprayer characteristics.

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Christina DiFonzo...They’re here…..Soybean aphids are colonizing soybeans just as plants emerge from the ground. The nymphs are on the new growth, and are difficult to see because they are on the hairiest part of the plant. On June 4 at MSU, my graduate student, Desmi, reported that 60 percent of the plants in one of her research plots had winged aphids. No predators were seen on the infested plants.

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Christina DiFonzo...Aphid numbers in many locations in the eastern Great Lakes area have come up, including locations in Michigan. It appears that early last week (July 23-25), a front moved west to east across the Great Lakes, with a counterclockwise circulation. Eventually the eastern edge passed over areas heavily infested with soybean aphid, especially Quebec.

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Christina DiFonzo...As in 2005 Monroe County, this summer we have at least one area, in eastern Saginaw County, where soybean aphids are over threshold (view photos). The fields I saw were specifically near Frankenmuth. I did not see buckthorn in the immediate area, but this part of Saginaw County is downwind from the Shiawassee and Titibawassee Rivers, and a national game area south of Saginaw City, all with a lot of buckthorn.

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Diane Brown-Rytlewski...There have been a couple of reports in Michigan of wheat with a red or yellow discoloration beginning at the flag leaf tip and progressing toward the base of the leaf. There is no stunting of the heads and minimal stunting of the plants. These leaf discoloration symptoms, along with stunted heads, stunted plants and flag leaves remaining in an upright position, are classic symptoms of barley yellow dwarf virus, an aphid transmitted virus.

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Christina DiFonzo...Aphid suction traps have been running in Michigan for the last several weeks. Last week, winged soybean aphids were captured in traps at the Kellogg Biological Station in Kalamazoo County and at the MSUE office in Monroe County. This is the first time winged soybean aphids were found in a suction trap before mid-summer flights in July. The suction trap network is running a bit earlier this year, which may explain why we are able to detect spring flight.

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Christina DiFonzo...There is good news and bad news related to soybean aphids...Entomologists from Illinois, Indiana, Ontario, Ohio and Michigan all report having a surprisingly difficult time finding soybean aphids on buckthorn, given the number of eggs this winter. It appears that the cold weather did reduce populations on exposed trees.

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Christina DiFonzo...This week there are reports of sprays going on for aphid infestations in wheat. Commercial companies are promoting intensive wheat management in Michigan, including managing fertility, weeds, diseases and insects. It is rare to have an aphid population in wheat in Michigan that merits spraying.

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Christina DiFonzo...Based on egg sampling this week at MSU, soybean aphid eggs made it through the winter, and they will hatch as buckthorn buds break in the next few weeks. Over the past four years, soybean aphid nymphs were found by mid-April in mid-Michigan, so egg hatch likely occurs in late March or early April in southern and central counties.

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Christina DiFonzo...This issue of the Field Crop CAT Alert includes an article by Terry Schulz and Kurt Thelen about seed treatments and soybean yield response. From a soybean aphid standpoint, I can confirm many of their findings.

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Christina DiFonzo...And to follow up on the previous article about suction traps, here is the latest update on soybean aphid in soybean.  Dave Ragsdale from the University of Minnesota reports that soybean aphid was found in multiple locations throughout Minnesota on V1 soybeans. The earliest find was in mid-May on volunteer beans along the Minnesota River in south-central Minnesota.

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Christina DiFonzo...Northcentral Regional Aphid Suction Trap Network was turned on last week in at least eight states. As in 2005, Michigan has three trapping locations that cover a north-south transect:  MSU’s Saginaw Valley Bean and Beet Research Farm in Saginaw County; the MSU Entomology Farm in Ingham County; and the Kellogg Biological Station in Kalamazoo County.

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Christina DiFonzo...A few weeks ago I reported that entomologists from Purdue and Illinois found only two aphid colonies in their annual buckthorn survey. Both colonies were found near Bronson, Michigan. (see photos) This week I hit the jackpot and found 22 colonies on a single buckthorn shrub on the MSU campus. Although there are dozens of other buckthorn shrubs in the area, none of the others had aphid colonies.

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Christina DiFonzo...Many of you are aware of the soybean rust web site (http://www.sbrusa.net/) sponsored by USDA last year. That site provides a map that shows soybean rust detections in sentinel plots and on kudzu, an alternate rust host. There is also commentary provided by state specialists. Knowing the progression of the disease north will help producers target scouting and apply preventative fungicide applications.

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Christina DiFonzo...In the first week of May, Dave Voegtlin from the Illinois Natural History Survey and Bob O’Neil from Purdue spent four days (1,300 miles) in Indiana, Ohio and Michigan looking for soybean aphid on buckthorn. Recall that buckthorn is the overwintering host for soybean aphid (SBA). Dave and Bob examined two known buckthorn hosts (Rhamnus alnifolia & R. cathartica) as well as “suspected” hosts (R. frangula and R. caroliniana).

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Kurt Thelen and Terry Schulz...Seed treatment insecticides such as Cruiser and Gaucho have been marketed for early season soybean aphid and bean leaf beetle control. Results from two years of performance trials conducted in Michigan indicate that soybean yield response to these seed-applied insecticides depends primarily upon the aphid pressure experienced during the early growing season.

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Christina DiFonzo...There are now two new seed treatments registered for soybean. Cruiser (thiamethoxam) was available in 2005; Gaucho (imidacloprid) can be used in 2006. Soybean seed can be ordered already treated, or treated by a commercial outfit after purchase. In most cases, insecticide-treated seed will also be fungicide-treated. The prices we were recently quoted for Cruiser and Gaucho treated seed were between $9 and $12 per unit (50 lb bag) = $10 to $14 per acre.

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Christina DiFonzo...General lessons from many trials in 2005
§      Scouting pays: Soybean aphid (SBA) problems were detected early by scouting and variability in infestation (and need for treatment) was also noted.
§      Residuals differ: OPs tend to have better initial kill but shorter residual. Pyrethroids tend to have longer residual.
§      Yields often don’t differ: In the end, however, yield generally depends more on spraying itself, then on choice of insecticide.
§      Coverage counts: Coverage probably explains many of the performance problems with various insecticides.
§      Tank mixing: Tank mixes of pyrethroids with Lorsban did not improve yield.
§      Reduced rates: Reduced rates of insecticides did not provide adequate control or improve yield.

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