Thrips dispersal and foliar sprays

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Virginia cotton requires a thrips control product at planting to preserve yield and avoid maturity delays. This is especially true since the arrival of tarnished plant bugs. Any maturity delay early-season will likely magnify plant bug injury. Cotton planted at the end of April and first week of May has put on 1-2 true leaves. It is time to scout for thrips injury and make foliar applications when necessary.

Levels of injury to cotton seedlings rated from ‘0’ (no damage) to ‘5’ (dead terminal
or plant) from thrips. Injury at ‘2-3’ or above approximates a threshold for intervention with an
insecticide application. (Photo and caption from Kerns et al., 2018)

Using a seed treatment alone will likely require a foliar spray based on research from the Tidewater AREC. In-furrow aldicarb and in-furrow imidacloprid with a seed treatment should not need a foliar spray. Scout cotton planted with in-furrow imidacloprid alone and determine if a foliar application is necessary (often it is not – saving you time and money).

All cotton planted in Virginia is under high risk for thrips injury. NCSU prediction model shows risk increasing in later-planted cotton. This model was highly accurate in 2018.

Tips for foliar applications: Consider plant-date and growing conditions. Cotton planted late-May into warm soil may not need a foliar spray. Do not apply foliar acephate if plants are growing fast with no to minimal thrips injury. Thrips injury is likely for all cotton planted in Virginia and risk will be high until plants are no longer susceptible. The three diagrams below from the NCSU model show when seedling susceptibility declines based on planting date (May 1, May 8, May 15). The blue line on these diagrams shows you when risk for thrips injury is highest.

Spraying is most effective when the first leaf is the size of a pencil tip to a mouse ear. I recommend a 6-8 oz. rate of acephate. Several scenarios may be responsible for reduced efficacy of sprays:

1. Rain. Acephate is not a rain fast product. Consider reapplying if necessary.

2. Resistance. Acephate at 3 oz. per acre has become less effective in spray tests. Rotate to Radiant if another spray is required or use a higher rate.

3. Species composition. Tobacco thrips are most common in VA, but western flower thrips can co-infest. Acephate is less effective on this species. Rotate to Radiant if another spray is required.

As always, call/text/email me with any questions. Good luck and happy planting!

Wheat Disease Update – May 9, 2019

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Fusarium head blight (FHB) risk is continuing to increase in parts of Virginia. Upcoming rain events will increase risk over the next three days (see figure below). Much of the wheat in the southern part of the state is past the vulnerable flowering stage, but wheat that is at or about to enter flowering may be at risk. Consider applying a fungicide if risk is moderate to high, especially on susceptible or moderately susceptible varieties. Fungicides should be applied at early flowering or up to one week later. Do not apply a strobilurin-containing fungicide since this can increase DON contamination. Recommended fungicides include Prosaro, Caramba, Proline, and Miravis Ace. Increased incidence and severity of leaf blotch and powdery mildew have been observed in some fields, and these fungicides will also provide control of foliar diseases.

Wheat Disease Update – May 1, 2019

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There is increased risk of Fusarium head blight (FHB) in some parts of Virginia, especially near the Northern Neck and Eastern Shore of Virginia. Wheat in much of the state is flowering, and if a field is in a high risk area a fungicide application is recommended. Recommended fungicides for control of FHB and DON contamination include Caramba, Prosaro, Proline, and Miravis Ace. Do not apply a strobilurin-containing fungicide after the flag leaf stage since this has the potential to increase DON concentrations in the grain. To maximize their effectiveness, fungicides for FHB and DON control should be applied at early flowering or up to one week later. Fungicides that control FHB and DON will also control foliar diseases including powdery mildew, leaf rust, stripe rust, and leaf blotch.

Wheat varieties vary in susceptibility to FHB and DON, and this should be considered when making decisions of whether or not to apply a fungicide at flowering for FHB control. The FHB Risk Tool (http://www.wheatscab.psu.edu/) allows you to select the susceptibility of your wheat variety to determine risk. You can find information on FHB susceptibility of your wheat variety from your seed dealer or in the Virginia Cooperative Extension Small Grains publication. The FHB Risk algorithm adjusts the relative risk based on the variety susceptibility as illustrated below. For assistance with small grains disease identification or for additional management recommendations contact Dr. Hillary Mehl, Extension Plant Pathologist (hlmehl@vt.edu).

FHB risk for susceptible (S) wheat, May 1, 2019.

FHB risk for moderately resistant (MR) wheat, May 1, 2019.

Wheat Disease Update – April 25, 2019

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Most of the wheat crop in Virginia is currently between flag leaf emergence and heading with some wheat close to the flowering stage. Foliar diseases including powdery mildew and leaf blotch have been observed in some fields, but overall levels of disease have been low so far. As wheat reaches the flowering stage, it is susceptible to infection with Fusarium head blight (FHB), and this is the critical stage for making fungicide applications. Currently, the risk for FHB infection is low throughout Virginia. In addition, the 3-day forecast indicates risk will remain low. FHB risk can be monitored using the Fusarium Risk Assessment Tool (http://www.wheatscab.psu.edu/).
Recommended fungicides for control of FHB and DON contamination include Caramba, Prosaro, Proline, and Miravis Ace. Do not apply a strobilurin-containing fungicide after the flag leaf stage since this has the potential to increase DON concentrations in the grain. To maximize their effectiveness, fungicides for FHB and DON control should be applied at early flowering or up to one week later. Fungicides that control FHB and DON will also control foliar diseases including powdery mildew, leaf rust, stripe rust, and leaf blotch. For specific wheat disease management recommendations or assistance with disease identification, contact Dr. Hillary L. Mehl (hlmehl@vt.edu). The 2019 Fungicide Efficacy Table for Wheat can be downloaded below.

NCERA 184 Wheat fungicide table 2019_Final

Aphids in alfalfa

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Large aphids populations have been observed in alfalfa this year following insecticide applications targeting alfalfa weevil. If you haven’t scouted for alfalfa weevil in Virginia, you should. See the bottom of this post for a weevil summary.

Aphids, typically pea aphids, can be problematic when their natural enemies are disturbed. They can reduce vigor and cause wilting in first cuttings. If early cutting is not an option, several insecticides (mostly pyrethroids) are labeled for their control. Low label rates are generally effective as long as you ensure good coverage. Scout for aphids by pulling 30 random stems per field and counting the number of aphids. This guide from Iowa State can help you make treatment decisions.

Most of the aphids I have seen in Virginia alfalfa are pea aphids (left) and cowpea (right). If you think you have another species, please give me a call or send an email.

Photos Erin Hodgson, Iowa State

My thanks to Lane Grow from Southern State Cooperative for his ongoing efforts to scout and report problems in western Virginia.

Alfalfa weevil information

Scout fields by pulling 30 random stems and inspecting foliage for weevils. Weevil larvae are small, can be white, yellow, or green, and have black heads. They are often tucked tight into new growth. It’s possible to dislodge larger larvae so be careful or collect stems into some container that catches these. I use a plastic freezer bag and insect stems in the shop or truck. This guide from Penn State can help you make spray decisions. Cutting alfalfa is an option if you don’t want to use pesticides. I recommend using clorpyrifos based on spray tests in 2018 and 2019. Some people have been successful with indoxacarb (Steward) or pyrethroids (many brand-name and generic options). Coverage is essential with any product.

 

Would Soybean Yields Rise If We Started Planting in April?

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April planting is thought to have an advantage over May planting because we can shift the development of soybean to an earlier time of the year  where there is more sunlight.   More total sunlight per day should result in greater yields.  But, does this hold up in Virginia?  Likewise, an earlier variety will also shift maturity, and the critical stages of development, to a time of the year when the days are longer.  So in theory, planting early-maturing varieties early should result in the greatest yields.

My concern is that when you shift your development to earlier times of the year, you are also placing the most critical pod and seed development stages in a hotter and drier time of the year.  While you could possibly alleviate the dry part with irrigation, I know of no way to keep the temperature from rising.

To test these hypotheses, we planted 10 to 12 varieties ranging in maturity from late-3’s to early-6’s in April, May, and June at three Virginia locations in 2017 and 2018.  I’m not going to show the data because we found relative maturity responded differently depending on location, and it would just take up too much room to show all the graphs.  However, we have seen no benefit to planting soybean in April versus May, although April plantings did not usually yield less than May plantings.  Maturity group response depended more on location and when the rain fell.

So, I suggest that you base your planting date and or relative maturity decisions on your need to spread out planting or harvesting.  April planting date is OK, but not necessary for greater yields.  Keep in mind that soils are usually cooler in April, so it will normally take soybean longer to emerge than when planted in May.  Fungicides will be needed for April and early-May plantings.

Planting a slightly earlier maturing soybean is usually OK also.  For more information on maturity selection, see my previous blog, “Improving Your Soybean Variety Selection Decisions – What maturity is best?”

If you do plant in April and/or want to use early-maturing varieties, then do this on your best soils.  If you move the critical stages of development to a hotter and drier time of the year, you’ll need the greater water-holding capacity of those soils.

Full-Season Soybean Seeding Rates: Maximize Your Yield and Reduce Your Risks

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In general, high seed costs have resulted in a reduction in the number of soybean seed planted per acre.  For our full-season production system, most have reduced their seeding rate to 140,000 or less.  Some have even had success with rates as low as 80 to 100 thousand seed/acre.  My research over the years has shown that we only need, on average, about 70 to 80 thousand plants/acre to maximize our yield.  But is this too low? Yes, it could be – in some situations.

There is also interest in varying seeding rates.  I said many years ago that it appears that this is possible.  But our approach to variable-rate soybean seeding will be just the opposite of how we vary our rates with corn.  With corn, we increase seeding rate as our yield potential increases.  With soybean, we do just the opposite – we reduce our seeding rate as yield potential rises.  But, how much can we reduce seeding rate with rising yield potential?

To answer both questions – Is a final stand of 70 to 80 thousand plants too low? and How do I vary soybean seeding rates?, I analyzed over 10 years (over 25 experiments from 2003-2011) of on-farm and small-plot research to determine the optimal seeding rate for three different yield potentials.  The results along with my recommendations are shown below.

For low yields of 20-40 bushels/acre:

Plant 120 – 140 thousand seed /acre.

Why not less?  The data to the left indicates that the optimal seeding rate (area between the two vertical dotted lines) ranges between around 100 to 120 thousand seed/acre.  Why is this not my seeding rate.  There is too much variability in the data; therefore too much risk.  In some years, yields could have been reduced with this rate.  So, I’m hedging towards less risk at these yield potentials.

 

For medium yields of 40 to 55 bushels/acre:

Plant 100 – 120 thousand seed/acre.

You will notice that the optimal seeding rate has declined to around 90 to 110 thousand seed/acre.  Note that this is only about 10,000 seed less that the previous graph, but I lowered my recommendation by 20,000 seed.  Why?  There is little variability in these data; hence, I have more confidence.

 

 

For high yields of 55 to 70 bushels/acre:

Plant 90 to 110 thousand seed/acre.

Like low yield potentials, I’m starting to hedge a little here towards less risk although my data indicates that I can go lower.  There were cases where is took nearly 120,000 seed to get the maximum yields.

 

 

One comment that I get with these data is: “These data are old.  Does it still hold up with newer varieties?”  A good question!  So, I’ve conducted seeding rate experiments over the past 2 years and I’ll continue this coming year.  To summarize, the most recent data has not changed my recommendations – I think that these trends still hold true.  However, we did see some differences last year – a year of wet and cloudy conditions.  The data are below:

With our maturity group 4 trials, we saw yield continue to rise with seeding rate, and our yields were in the high range (about 50 to 60 bushels/acre).  But yields with the group 5 soybeans tended to level off at about 120 thousand seed/acre.   Why a different response and why did maturity group matter?

 

 

I think the answer is lack of sunlight.  Total photosynthetically-active radiation interception differences are one of the reasons that we get yield responses to seeding rate.  In most cases, this is a lack of leaf area; we are not intercepting all the light.  But, this was not the case in 2019.  We had what I normally consider enough leaf area, at least enough for a sunny year.  But we had less light in 2019.  The group 5 soybean did have more leaf area than the group 4 soybean; I’m assuming that these few extra leaves made up a little for the lack of light.  Cloudiness is one of the risks we take.  Still, I won’t change my recommendations based on last year since it was rather unusual.

In conclusion, if you want to chose the best full-season seeding rate in Virginia for your yield potential, my recommendations are:

Low yields: 120 to 140 thousand seed/acre

Medium yields: 100 to 120 thousand seed/acre

High yields: 90 to 110 thousand seed/acre

 

Herbicide Resistant Weeds Workshops Slated for Maryland, Virginia, and Delaware

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A series of half-day workshops will be held in Maryland, Delaware and Virginia this winter for farmers interested in learning about the problems of herbicide resistant weeds and how to manage them. Hosted by University of Maryland Extension in collaboration with Virginia Tech and University of Delaware, these workshops are designed to equip farmers with the knowledge to improve weed control on their farms.

Farmers in the mid-Atlantic area are starting to see the impact of herbicide resistant weeds on their crop yields. With many problematic weeds now found throughout the region it is essential that farmers learn the key management strategies to control these weeds.

Sessions will cover integrated weed management tactics; palmer amaranth, common ragweed and marestail control strategies; and developing a weed management plan. There is no charge to attend and lunch will be provided. Pesticide (commercial and private) and CCA continuing education credits will be offered.

Workshop locations and times are listed below. Please RSVP to the respective meeting location to provide an accurate meal count.

February 25th (12 pm to 5 pm) Old Beale Sanctuary, 369 Queen Street,Tappahannock, VA 22560

To register call the Essex County Extension Office: at (804) 443-3551

February 26th (8 am to 1 pm) St. Mary’s County UME Office, 26737 Radio Station Way, Leonardtown, MD 20650. To register call the St. Mary’s County UME Office at 301-475- 4484

March 4th (8 am to 1 pm) Harrington Volunteer Fire Company, 20 Clark St, Harrington, DE 19952. To register call the UD Carvel REC, at 302-856-2585 (ext 540)

March 5th (8 am to 1 pm) Somerset Extension Office, 30730 Park Drive, Princess Anne, MD 21853. To register call the Somerset County Extension Office at 410- 651-1350

March 6th (8  am to 1 pm) Frederick County UME Office, 330 Montevue Lane, Frederick, MD 20712. To register, call the Frederick County UME Office at 301-600- 3576

March 7th (8 am to 1 pm) Chestertown Volunteer Fire Company, 211 Maple Ave, Chestertown, MD 21620. To register call the Kent County UME Office at 410-778- 1661

For more information contact Ben Beale at 301-475-4481, Michael Flessner at 540-315-2954, Matt Morris at 301-600-3578 or Mark VanGessel at 302-856-7303.

Dicamba Training Opportunities

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If you intend to apply Engenia, Xtendimax, or FeXapan this year, you need to complete the annual dicamba specific training requirement in addition to being a certified pesticide applicator. In Virginia, this training is conducted by the registrants (manufacturers), but can also be completed in another state including registrant training, state mandated training, and state approved training. Both in person and online training is acceptable. Training is not product specific; you do not have to take the training from the registrant of the product you apply.

Make sure to document your training.

Here are links to find a training event near you or complete online:
BASF

Bayer

Corteva

University of Nebraska

Please note that some some events require pre-registration.

The following links are under revision for 2019 but will be useful shortly:
Mississippi State Extension

2019 Virginia Peanut Production Guide

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  • The new 2019 Virginia Peanut Production Guide is available at this link https://pubs.ext.vt.edu/SPES/SPES-67/SPES-67.html
  • This guide describes peanut production practices including cultivars, planting, management, and harvest. Under management, information is provided on the optimum time for nutrient and irrigation applications; describes rotations effect on yield; soil preparation, etc. It also identifies major pests for the region including weeds, insects and disease, and how those to be controlled.
  • Archived Peanut Production Guides can be accessed from: http://www.sites.ext.vt.edu/newsletter-archive/peanut-production/index.html