The 2019 growing season in Virginia is one that has been marked by a good planting window in early May resulting in a sizable portion of Virginia cotton planted in the first two weeks, followed by spotty rainfall events across the growing region with most areas receiving adequate rainfall throughout the season. Couple the early planting date with light overall insect pressure early during the reproductive period resulting in higher than normal fruit retention across Virginia. Yes, there have been pockets of high pressure from tarnished plant bugs, but for the most of Virginia pressure as been light through June and July. Cotton was flowering by July 4th in 2019 with early planting and entering week 5 or 6 of bloom by the first week in August. Data in Virginia show that nutrient concentrations in leaves and petiole decrease rapidly from the 1st to 4th weeks of bloom, indicating the plant is beginning to shut down in terms of nutrient uptake. After the 4th week of bloom nutrient concentrations level off at lower concentrations. With dropping petiole and leaf nitrate-N, sulfur, and potassium, fields will begin to show signs of nutrient deficiencies and overall yellowing or reddening. These areas will be more pronounced in sandier areas first then spread into heavier textured soils.

First, producers and/or crop consultants should evaluate nodes above white flowers (NAWF) to determine if cotton has reached “cutout”. Cutout has been described as the point at which NAWF < 4 or 5. Cotton that has fallen below this threshold and exhibiting overall yellowing or reddening will be at “cutout”. These symptoms usually occur towards the latter part of August in Virginia, but given higher fruit retention in 2019 coupled with an early planted crop and high heat unit accumulation these symptoms will occur sooner in 2019.

One may worry if your crop has low boll retention, also commonly referred to as “missing positions” and is exhibiting the symptoms of cutout. . Insect damage and other environmental conditions resulting in low fruit retention typically will delay maturity thus cotton will stay greener longer and exhibit a high level of vegetative growth. In this case, review rainfall data and nutrient management strategies as some environmental condition may have increased nutrient loss thus reducing crop uptake resulting in premature cutout. An example may be a large rainfall event leached a significant portion of nitrogen/sulfur/potassium thus cotton is running out of nutrients. There is no management strategy that will “make up yield” in this situation at this point in the season, however nutrient management strategies could be tweaked in future years to hedge potential losses in the future.

Earlier than normal cutout does not signify the need for higher rates or additional applications of nutrients, especially if boll retention is high and heat unit accumulation is appropriate for that growth stage of the crop. This is the natural senescence (entering dormancy) for cotton and is a positive when discussing defoliation and harvest aid applications. For Virginia, the last effective bloom date is around Aug. 25-31, so even though cotton has reached cutout early this does not mean it is no longer susceptible to insect pressure. Continue to scout and follow Dr. Sally Taylor’s recommendations to protect later bolls, which can represent around 10% of lint yield.

For further questions or concerns feel free to contact me at whframe@vt.edu and/or 757-807-6539.

Please come out to the 2nd Annual Virginia Cotton Growers’ Association Field Day on Friday August 16th from 7:30 AM – 12:30 PM. The field day will be at the Virginia Tech Tidewater Agricultural Research and Extension Center Hare Rd. Farm. The address is 1045 Hare Rd., Suffolk, VA, 23437. Registration starts at 7:30 AM and field tours will begin at 8:00 AM. Topics will include mid- and late season insect management, nematode management, subsurface drip irrigation, enhanced efficiency fertilizers in cotton, variety selection and management (via industry reps), and cover crop management in cotton. There will be Private Pesticide recertification credits. Please contact Dr. Hunter Frame if you have any questions about the field day at whframe@vt.edu or 757-807-6539.

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 16^th 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.

Happy August!