Recently, soybean aphids have been confirmed at higher populations than typically expected in August. While many folks are scouting for worms and stinkbugs, we also recommend looking for aphids in your soybean fields as well. The key variables to consider regarding managing soybean aphids are the number of aphids per plant and the soybean growth stage. Information from our Pest Management Guide on Soybean Aphids in summary including info on thresholds and sampling are as follows (VCE Field Crops PMG, Publication 456-016):
Number of aphids per soybean plant
The current economic threshold for aphids is an average of 250 aphids per plant, on two consecutive field visits spaced about 5-7 days apart. This is because aphid populations can “crash” quickly due to heavy pressure by natural enemies like lady beetles, parasitic wasps, and fungal diseases. When scouting, choose a “Z” or “W” shaped pattern to cover the entire field and sample at least 20 to 30 plants per field by examining the entire plant, including stems and upper and lower leaf surfaces. Use the aphid/plant average for determining the need for treatment.
The soybean growth stage
The threshold of 250 aphids per plant applies to soybeans through the R5 growth stage (3 mm long seed in the pod at one of the four uppermost nodes on the main stem), after which time plants can tolerate 1,000+ aphids with no threat to yield. If an insecticide is applied for aphids, pyrethroids (e.g. bifenthrin, Warrior II, Mustang Max, etc.) can be effective for management, but choosing a more selective insecticide can preserve natural enemy populations and limit future flare ups of aphids or other pests.
Captures of AGB adults in our Sussex County, VA black light trap dropped sharply in July and we shut down the trap. Here is the graph for the entire season:
Thanks to the folks at this location for allowing us to conduct a second year of monitoring this insect!
Asiatic garden beetle numbers in our Sussex County, VA black light trap dropped this week, with 60 adults total caught in the past 3 nights (Figure below).
Carrie Ortel, Extension Soybean Agronomist, Virginia Tech Tidewater AREC
Mark Reiter, Soils and Nutrient Management Extension Specialist, Virginia Tech Eastern Shore AREC
Joseph Haymaker, Postdoctoral Associate, Virginia Tech Eastern Shore AREC
Many of the full-season soybean fields in Virginia are beginning to flower, which is a great time to start tissue testing if there is a concern for crop nutrition. Tissue testing is an effective way to monitor crop nutrition when done correctly. To get reliable results, choose the correct, uppermost fully expanded soybean leaf during optimal conditions and carefully interpret the results. Tissue testing may begin as early as V4 but is most reliable during flowering and can continue through pod filling.
Step 1: Plan Your Sampling During Good Field Conditions
Time It Right – Field Conditions Matter
Field conditions at sampling time greatly affect the accuracy of tissue tests. Aim to collect samples when plants are actively transpiring, which usually means:
Adequate soil moisture (not drought or waterlogged).
Moderate temperatures and healthy plant function.
Avoid sampling during:
Drought, which can limit nutrient uptake even when nutrients are present in the soil.
Saturated soils, which can temporarily inhibit root function.
Shortly after foliar nutrient applications—wait at least a week and ensure a rain event has occurred to allow nutrients to be absorbed and leaf surfaces to clear.
Address In-Field Variability
Soybean nutrient levels can vary within a field due to differences in soil texture, drainage, or previous management practices. For meaningful results:
Divide fields into management zones based on known variability.
Take one composite sample per zone, collecting at least 18 trifoliolate leaves randomly throughout that area (Ortel et al., 2023).
This helps identify localized deficiencies and supports more precise nutrient management.
Step 2: Collect Your Leaf Sample
Choose the Right Plant Part
To get consistent and accurate results, it’s critical to sample the correct, uppermost fully expanded trifoliate leaf, as nutrient concentrations differ between leaves. The uppermost fully expanded trifoliate leaf is typically located on the second, third, or fourth node from the top of the plant (Figure 1, shown below).
Figure 1. Soybean plant at the full flower (R2) growth stage. The uppermost fully developed leaf is shown as the leaf on the third node from the top of this plant.
Look for the highest leaf that is dark green, full-sized, and has a coarse texture.
Avoid leaves with a velvety feel or are lighter in color than others—these are still developing and can falsely indicate nutrient levels.
Check with your testing lab for specific guidelines. Some labs also recommend sampling the whole plant during vegetative stages or including/excluding the petiole (the stalk attaching the leaf to the stem). Be sure your sampling method agrees with the lab’s interpretation standards.
Collect the Sample Properly
Once you identify the correct leaf, follow these best practices:
Collect 18–25 leaves per sample for a good composite.
Take samples across a consistent management zone (based on yield history, soil type, or other field characteristics).
Place leaves in a paper bag (not plastic) to allow drying and prevent mold.
If your lab uses critical nutrient thresholds without the petiole (e.g., Virginia Tech), remove the petiole before bagging.
Step 3: Interpret Results with Context
Getting accurate lab results is only half the process—understanding them correctly is essential.
Use growth-stage-specific critical concentrations when available, such as potassium in soybean (Slaton et al., 2021). These values indicate the threshold below which yield may be affected.
If no critical values are available, use sufficiency ranges cautiously—they are less precise and based on broader surveys instead of replicated research.
Also, consider nutrient mobility:
Mobile nutrients like nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) can move within the plant and are often relocated from leaves to developing seeds and pods (Bender et al., 2015). Lower concentrations in leaves during reproductive stages may not signal a deficiency.
Immobile nutrients like calcium (Ca), sulfur (S), and most micronutrients remain in their original locations and offer more stable indicators.
Although some nutrient deficiencies may not be visually apparent (hidden hunger), only take action with a corrective application of fertilizer if a deficiency occurs. Prophylactic foliar fertilizer applications have not been shown to increase yields (Matcham et al., 2021). When a nutrient deficiency does occur, a corrective application of granular fertilizer should be used to correct macronutrients, while a foliar fertilizer may be used to correct micronutrients.
Take Home Points
Collect a composite sample of at least 18 of the uppermost fully expanded soybean trifoliate leaves from each management zone.
Only collect tissue samples during favorable field conditions and adequate soil moisture.
Consider the plant part collected (petiole included or excluded), growth stage, and nutrient mobility with interpreting results.
Bender, R. R., Haegele, J. W., & Below, F. E. (2015). Nutrient uptake, partitioning, and remobilization in modern soybean varieties. Agronomy Journal, 107(2), 563–573. https://doi.org/10.2134/agronj14.0435
Matcham, E. G., Vann, R. A., Lindsey, L. E., Gaska, J. M., Lilley, D. T., Ross, W. J., Wright, D. L., Knott, C., Lee, C. D., Moseley, D., Singh, M., Naeve, S., Irby, J. T., Wiebold, W., Kandel, H., Lofton, J., Inman, M., Kleinjan, J., Holshouser, D. L., & Conley, S. P. (2021). Foliar fertilizers rarely increase yield in United States soybean. Agronomy Journal, 113(6), 5246–5253. https://doi.org/10.1002/agj2.20889
Ortel, C. C., Roberts, T. L., Hoegenauer, K. A., Poncet, A. M., Slaton, N. A., & Ross, W. J. (2023). Mapping variability of soybean leaf potassium concentrations to develop a sampling protocol. Agrosystems, Geosciences and Environment, 6(4). https://doi.org/10.1002/agg2.20439
Slaton, N. A., Drescher, G. L., Parvej, R., & Roberts, T. L. (2021). Dynamic critical potassium concentrations in soybean leaves and petioles for monitoring potassium nutrition. Agronomy Journal, 113(6), 5472–5482. https://doi.org/10.1002/agj2.20819
The entomology program at the Tidewater AREC has continued to monitor Asiatic garden beetle adults in our black light trap. The population peak in early June 2025 (see Figure) is very similar to what we saw in early June of 2024. Much of our cotton now has enough growth on it that some defoliation can be tolerated–but similar to thrips, I would recommend keeping an eye on anything that has not reached 4-5 true leaves.
Asiatic garden beetle (AGB) captures in our Sussex, VA black light trap spiked the first week of June, totaling 1,281 adults over a 7-day span. Some severe AGB foliar injury to seedling cotton was reported near Wakefield (image below). We dug up cotton plants and marestail in AGB hotspots, finding adults under each, but we do not have evidence that they feed on cotton roots. For more information, please see our Virginia Cooperative Extension publication, “Asiatic Garden Beetle in Cotton”
On Monday, May 26 the Tidewater AREC entomology team collected tobacco thrips from cotton throughout southeastern Virginia. These populations were sent to the University of Tennessee where they were tested in the lab for susceptibility to acephate, spinetoram (Hemi SC or Radiant), and dicrotophos (Bidrin). Across all the sites, the results were very consistent with;
75-79% mortality with acephate 100% mortality with spinetoram 47-50% mortality with dicrotophos
We would classify this as tobacco thrips having reduced susceptibility to acephate in southeastern Virginia. Acephate resistance was also previously confirmed in northeastern North Carolina, just across the state line. This year we have found a high proportion of flower thrips, which are harder to kill with acephate, and now have confirmed that acephate has reduced efficacy for tobacco thrips. If you still plan to make a foliar thrips application, or are making a second application after a previous acephate application, Hemi SC (spinetoram) should be considered for more effective control. See this previous blog post for more details on the importance of timing your foliar application for maximum economic return.
We’d like to thank Sebe Brown at the University of Tennesee and his team for running the lab tests and the Virginia Cotton Board for sponsoring this research.
It has been a cool and wet start to the cotton season in southeast Virginia, and growth is slow. With a slow start to the season some folks are considering a second foliar application for thrips management. There are a couple key things to consider…
The first thing to consider for effective thrips management is timing
The most consistent return on investment comes from a foliar application early in the first true leaf stage. An application at the second leaf stage sometimes pays off, which is more likely to be the case with our current growing conditions. If cotton reaches the three or four-leaf stage, foliar applications made for thrips rarely pay off.
The next consideration is what insecticide to chose.
One of the most commonly used products to control thrips with a foliar spray is acephate. There are two thing to consider when using acephate; 1) western flower thrips are not as susceptible to acephate as tobacco thrips, and 2) acephate resistance has been documented in tobacco thrips in northeastern North Carolina, just across the state line from us in southeastern Virginia.
Populations of western flower thrips have been high so far in southeastern Virginia.
In several trials at the Tidewater AREC in Suffolk, we found around 80% western flower thrips in a foliar insecticide trial. Additionally, collections made from grower fields throughout Suffolk and Southampton counties on May 23 averaged 73% western flower thrips. While most fields did have a majority of western flower thrips, it is important to note that it varies between fields even across a relatively small area, and some sampled fields had a larger proportion of tobacco thrips. A table of thrips collections from May 23 can be found below. Each row represents a sample of five cotton plants in a field in Suffolk or Southhampton county.
Field
Tobacco thrips
Western flower thrips
% Western flower thrips
#1
2
6
75%
#2
2
13
86%
#3
1
4
80%
#4
4
23
85%
#5
11
3
21%
#6
1
9
90%
#7
1
8
88%
#8
4
4
50%
In the foliar insecticide test at the TAREC, acephate (at 3 oz/ac) did not provide better control than not treating with these high populations of flower thrips. Hemi SC (spinetoram), provided good thrips control at both the 2.5 and 3 oz rates. Hemi SC is the same active ingredient found in Radiant and is available for use in Virginia and the Carolinas this year for thrips suppression. It is important to mix Hemi SC with a non-ionic surfactant or with an herbicide which already contains a surfactant, to get good thrips control.
If you are using acephate, you should carefully monitor the performance of the application in your field. If you are not satisfied with the performance of an acephate application, the cotton growth stage and the growing conditions at that time should be assessed before considering a second application. If a second application is made, Hemi SC should be considered for more effective control and to rotate the insecticide mode of action. Bidrin should not be used for a second application after acephate, as these two insecticides are the same mode of action.
Both acephate and spinetoram can be washed away by rain up to 8 hours after application (or possibly longer), but acephate is slightly less susceptible to being washed away when comparing the two. However, some protection from a foliar application is better than none under current conditions, which are expected to extend through this weekend.
As a reminder, if you are planting Thryvon cotton, it provides excellent thrips control and does not need a foliar application. If you have any thrips questions contact Tim Bryant (757-621-8804, btim2@vt.edu), field crop entomologist at the TAREC in Suffolk, VA.
Douglas S. Higgins, Assistant Professor and Extension Specialist, Virginia Tech Eastern Shore Agriculture Research and Extension Center
In Virginia, wheat is currently at varying growth stages across the state. Many fields are at the boot stage (Feekes 9) or beginning to head (Feekes 10.1 to 10.3), while in some areas and in early-maturing varieties heads are fully emerged (Feekes 10.5).
For those choosing to make a fungicide application, the optimal timing for managing scab is at early flowering (Feekes 10.5.1) and up to seven days afterward (see figure below). Reminder: Do not use products that contain strobilurins (FRAC 11) to manage scab.
Warm, humid, and wet conditions leading up to and during flowering favor infection by the scab-pathogen. As of April 25, 2025, conditions in Virginia are not favorable for disease development in flowering wheat. However, for fields expected to flower in the coming days or weeks, monitor your local weather closely and consult the Fusarium Risk Tool (https://www.wheatscab.psu.edu/) for updates on disease-conducive conditions.
