Ed Seymore, our soybean aphid scout has reported finding above threshold numbers (500+/plant) of soybean aphid in fields in southwest Fauquier Co and northwest Culpeper Co. These aphid populations have been increasing over the past two weeks and are in late planted beans that are in the R3-R4 growth stage. This fits the scenario for a treshold, as best we understand it.
Category Archives: Soybean
Corn earworm and pyrethroid susceptibility, soybean aphid, and Mexican bean beetle update
Corn earworm and pyrethroid susceptibility, soybean aphid, and Mexican bean beetle update
CORN EARWORM: Moths are continuing to exhibit high levels of survivorship in our adult pyrethroid vial tests (see the attached line graph). We are striving to test several hundred moths each week as we feel this is important information for growers. As of this week, we are hearing of some fields where growers are getting less than satisfactory results with their pyrethroid sprays.
Earworms are reported to be in peanut, cotton and soybean fields in our area. It is time for folks to begin scouting throughout the state. In areas that are mostly dry, the problem is worse. In wetter areas, numbers are slower to build. The moth flight is increasing gradually, but has still not peaked. Rains are keeping the corn green, which tends to hold them in the corn, and in general, moth activity is less during rainy periods. Moth activity is higher in dry areas. If things dry out over the next two weeks, we can expect a large flight. But if it stays wet, the moth flight and subsequent earworm numbers will be suppressed.
SOYBEAN APHID: Weather conditions (generally cool in the low to mid 80s/wet) are nearly perfect for soybean aphid survival in some parts of the state and consequently, we are getting reports of high numbers in some areas. We will provide more detail next week, but as of today, many fields in the Gloucester/Mathews area, the Goochland area and the Shenandoah Valley have populations. I recently spoke with one of the entomologists in the north central states who was part of the large effort to develop the soybean aphid thresholds and here are his main ‘talking points’. Thresholds only apply up to the R5 growth stage. After that, beans can withstand 1000s per plant with no detectable problem. From R1-up to R5, the threshold is 250/plant IF POPULATIONS ARE INCREASING. Even maintaining at 250/plant does not result in a yield loss. An insecticide application at 250, when populations are increasing, prevents that increase. This is an important concept to be aware of. It takes consecutive field visits and good record keeping to determine if the population is holding, increasing, or decreasing due to predation by predators (lady beetles for example). He also warned that tank mixing an aphid insecticide (a pyrethroid) with a herbicide will only provide aphid control if the spray system is set up for high volume (10 + gpa) and small droplet size. The large droplet systems used for herbicides will not work well for aphids. Hollow cone spray patterns with small droplet size are needed to get product to circulate throughout the soybean canopy, to the undersides of leaves where aphids are feeding.
MEXICAN BEAN BEETLE: Prior to when I came to Virginia (in Aug 1988) Mexican bean beetle had been a major pest of soybeans. For a number of debatable reasons, in the years just before I arrived populations crashed. Since then I have seen them a total of two times in isolated areas, only in years and areas where it stayed wet and cool (relatively) all summer. Galen Dively in Maryland reported today that they are seeing a few outbreaks on the Maryland Eastern Shore. As cool and wet as it is in some parts of Virginia, it would not surprise me to hear of a few outbreaks. Keep a watch out for them. They do the worst damage when they go undetected in the first couple of generations. They gradually build to higher and higher numbers until the last generation, and in what appears to be ‘overnight’ they can totally defoliate a soybean field¬ a pretty sight.
Additional information: cew-cyper-aug-13-09-herbert-ppt
Summary of 2009 thrips research in soybean
The attached Word document contains data tables summarizing Dr. Herbert’s 2009 thrips research in soybean. Trials are still in progress. Additional information: soybeanthrips-doc
Slugs in soybean: What to do.
I have been getting a lot of calls this week about slugs in soybeans. They are a bigger problem this year in some areas because of the cooler, wetter spring/early summer. They are also typically worse in high-residue fields. Although we have had slug problems in both corn and soybean (even a few in cotton), we are not experts in management. We have been communicating with Dr. Ron Hammond at Ohio State University, who is an expert. I know Ron well. He and I have been serving on a soybean/insect regional project for many years and I have a lot of respect for him. Because of the more consistent pressure in his state, several years ago he took on the responsibility of doing slug management research.
Here are a few of the common questions that I have been getting, and some of Ron’s comments.
Question: I have lost my soybean stand and am considering replanting. Would tilling the field help get rid of the slugs?
Ron: “Tilling the field would probably help. However, if slug numbers are high, it might not get enough of them. But overall it should help. A good no-tiller will not do this however. As temps and soils warm and dry up, things will get better because seeds will germinate faster and plants will grow. Galen Dively (University of Maryland) normally suggests late plantings for this reason, as that is when the slug cycle tends to end. Just hope and pray for better weather. That’s what we do. Remember that the slugs are still there, just bigger and hungrier!”
Deadline (by AMVBAC) is the only registered product that will provide good, even excellent, control of slugs. It contains the active ingredient, metaldehyde. There are two mini-pellet formulations, M-Ps which are blue colored, and Bullets, which are tan colored. Most growers prefer the M-Ps as they are easier to see on the ground and make it easier to calibrate the applicator. If Deadline is applied when slugs are present, they will be attracted to it and will feed on it. But keep in mind the pellets do not stay active for more than a few days, and almost any amount of rain rinses out the active ingredient. A 10 lb/acre rate is sufficient, expensive, but effective. Consider treating the worst areas.
Question: What about Larvin? I have read that Larvin will kill slugs.
Ron: “Here is the scoop. Back in the 1980s, we had a grower-prepared bait for corn in Ohio that mixed cracked corn, beer, molasses, and mesurol for slug control. It was a state label. Never could get it for soybean. When soybean began being grown no-till, slugs then became a soybean problem. But we could not use the above bait. However, we found out that Larvin has molluscicidal properties, and got the exact same state label for soybean, but with Larvin rather than mesurol. Worked great. Remember that Larvin has a label on soybean as foliar, so has an EPA tolerance. Also remember that being a carbamate, Larvin has more impact on other things then does metaldehyde. Because of supposed bird kills, the company at the time pulled support of the label. So nobody has the ability to legally use it this way anymore. I checked into it for future use and was basically told, don’t bother…but yes, Larvin will kill slugs, is just NOT LEGAL.”
So what should you do? First consider delaying replanting until the weather straightens out. Delaying planting until it is warmer and drier could be the best approach. If you cannot delay planting, Deadline is the only legal and effective option.