Our first confirmed identification of white sugarcane aphid occurred this week. A BIG thanks to Laura Siegle in Amelia County for her vigilance and sharp eye. What does this mean for sorghum growers? It is time to scout. At least once per week until aphids are spotted in the field. Following that and until threshold is met – scout twice per week. Numbers can increase quickly. Start scouting on the borders of fields. Aphids will infest borders first. Check the underside of leaves. Not every aphid you find is a sugarcane aphid. You can bring samples to me or your local agent.
Corn earworm are likely found in sorghum this time of year. The same products will not kill both sugarcane aphids and corn earworm. Only Transform and Sivanto Prime are labeled for white sugarcane aphids in Virginia. Scout for earworms by beating sorghum heads into a 10-gallon bucket. A rough threshold is 2-4 worms per head. A threshold that includes costs of application and sorghum prices can be found here.
I made an error this week in my Southeast Ag Fax post and referred to the last spray date in cotton as “cutout.” What I should have said is, cotton should be sprayed for an above threshold plant bug population until the bolls that you anticipate harvesting are past susceptibility (~250dd). This may or may not coincide with cut-out (4 nodes above white flower). Keep in mind that, as the season progresses, sprays will offer less of a yield benefit. In Virginia, our critical window of protection is early to mid-bloom. There is a small and real yield benefit in spraying until week 5 or 6, but the lint gain may not offset the cost of applications. Late planted cotton is at high-risk because it overlaps longest with large bug populations and the plants have less time to compensate.
This season, there has been very poor performance of pyrethroids against plant bugs. Bifenthrin (Brigade and generics) performs better than other active ingredients including lambda-cyhalothrin (Karate, Besiege, Warrior II, Lambda-Cy) and beta-cyfluthrin (Baythroid). Acephate (Orthene 97) and sulfoxaflor (Transform) are better products. Diamond, an insect growth regulator that targets nymphs, should be tank mixed with either acephate at 8 oz. or bifenthrin at 6.4 oz. Currently, I do not recommend Diamond with other products without consulting your Amana representative. Diamond is added to prevent infestation and kill nymphs. It may not have quick knock-down. We have tested Diamond’s residual until two weeks post spray. Acephate alone works well at 8 oz. and is not rain fast. I have concerns with acephate and aphid populations that I will discuss this in another post. Both Bidrin and acephate are effective against plant bugs and stink bugs. For bollworms, I recommend Prevathon or Besiege. A well-timed pyrethroid spray may work and it will need to target small worms before they move inside of squares and bolls. Overall, stink bug pressure is moderate and bollworm pressure is light to moderate. Eggs and small worms have been spotted in low numbers in two-gene cotton. Please keep in mind that I am rarely called when insecticides work well. Keep me posted if your specific combination looks terrific!
Our cotton field day is on August 16th at the Tidewater Research Station. Seth Dorman and I will cover insect sprays, scouting techniques, and other topics. Josh Holland, ANR Southampton, and I will provide portable summary tables of product performance (as we have measured in 2019 on-farm trials).
Thanks to Stan Winslow from Tidewater Ag for his advice and video evidence that big-eyed bugs eat plant bugs. Thanks to Josh, Seth, and the TAREC team for their continued scouting efforts.
Corn earworm moth catches are increasing for most black light stations; nightly averages this week were: Greensville=25.1; Prince George (Templeton)=5.7; Prince George (Disputanta)=3.7; Warsaw=46.4; Southampton=9.0; Suffolk=14.6.
Preliminary results from our annual survey of field corn show the following percent infested ears (based on sampling 5 corn fields/county, 50 ears per field, for evidence of corn earworm larvae): Accomack=16.0 percent infested ears; Amelia=15.6; Chesapeake=5.6; Dinwiddie=19.6; Essex=11.6; Greensville=32.8; Hanover=32.8; Isle of Wight=17.6; King & Queen=13.6; King William=24.4; Lancaster=4.8; Northampton=11.2; Northumberland=4.0; Prince George=12.8; Southampton=11.2; Virginia Beach=17.6; Westmoreland=12.8. Thanks to the following for collecting data from their counties: Eastern Shore AREC entomology; Laura Siegle; Watson Lawrence; Mike Parrish; Robbie Longest and Brittany Semko; Sara Rutherford; Laura Maxey-Nay; Livvy Preisser; Trent Jones; Scott Reiter; Joshua Holland; Roy, Bailey, and Fletcher Flanagan; and Stephanie Romelczyk and Amerah Thompson.
We have found bollworm eggs and small larvae in our cotton experiment in Suffolk. Please be sure to scout your fields.
For soybean that is at or near the beginning pod (R3) stage, it is time to consider whether or not a fungicide application is needed to control foliar diseases and protect yield. The Virginia soybean fungicide advisory indicates that disease risk is moderate to high in most locations. Fields with moderate risk should be scouted since foliar diseases will not be an issue in every field every year. Keep in mind that other risk factors also contribute to disease severity and yield loss to fungal diseases. High risk fields include those where susceptible soybean varieties are planted, there is a recent history of soybean foliar diseases, and/or rotations out of soybean are short or soybean is planted continuously over several years. If based on the soybean fungicide advisory or other factors you decide to apply a fungicide, applications are generally the most effective when applied between R3 and R4 stages (no later than R5). The most recent Soybean Fungicide Efficacy Table and instructions on how to use the Virginia soybean fungicide advisory can be found in last week’s blog post. A summary of disease risk and spray recommendations for different locations in Virginia can be found below.
Region of Virginia
Location of weather station
Soybean disease risk
Moderate to high
Low to moderate
Moderate to high
For detailed daily advisories, select the location closest to your field and download the corresponding file here:
As August approaches, now is the time to be scouting peanuts for leaf spot and soilborne diseases and making timely fungicide applications. Calendar-based or advisory-based spray programs can be followed, but be sure to make your fungicide applications before rainy weather makes it difficult to get into fields. Many of our leaf spot outbreaks over the past couple of years were due to extended periods of rainfall and delayed fungicide applications. Cooler, wet weather over the past several days has increased the risk for Sclerotinia blight. In our research plots at the Tidewater AREC, we found small amounts of late leaf spot, Sclerotinia blight, and southern stem rot this week. The leaf spot and Sclerotinia blight advisories, which can be found on the Peanut Cotton Infonet website, indicate disease risk is currently high. For fungicide recommendations, contact your county extension agent or Dr. Hillary Mehl (email@example.com).
Based on research conducted since 2014, we have developed a disease favorable day threshold for predicting when a fungicide application in soybean will be economical. The favorable day threshold is based on daily average temperature and hours of high relative humidity, and these parameters are being monitored from weather stations located at Virginia Tech Agricultural Research and Extension Centers (AREC) throughout the state. We have determined that weather conditions approximately three weeks prior to the beginning pod (R3) stage of the soybean crop are the most critical for determining if disease will impact yield and if a foliar fungicide application will be economical. Fungicide recommendations for different locations throughout Virginia can be downloaded below. To use the advisory, follow these steps:
1) Identify the weather station (AREC) closest to your field. A map of the AREC locations can be found here.
3) Under the “date” column, find the date that corresponds to approximately when your soybean crop has reached or will reach the R3 (beginning pod) stage).
4) In the row that corresponds to your R3 date, determine if disease risk is low, moderate, or high based on the favorable day threshold.
5) The last column indicates if a spray is recommended based on your R3 date.
Keep in mind that other risk factors also contribute to disease severity and yield loss to fungal diseases. High risk fields include those where susceptible soybean varieties are planted, there is a recent history of soybean foliar diseases, and/or rotations out of soybean are short or soybean is planted continuously over several years. If based on the soybean fungicide advisory or other factors you decide to apply a fungicide, applications are generally the most effective when applied between R3 and R4 stages (no later than R5). The most recent Soybean Fungicide Efficacy Table can be downloaded below.
Small Grains in 2019 present results from barley and wheat varietal tests conducted in Virginia in 2017-2019. Small grain cultivar performance tests are conducted each year in Virginia by the Virginia Tech School of Plant and Environmental Sciences and the Virginia Agricultural Experiment Station. The tests provide information to assist with cultivar selection.