I have had a few questions about starting a peanut fungicide program on slow growing or late planted peanuts recently. The rule of thumb date I typically use is if you haven’t sprayed for leaf spot by July 10th, go ahead and start making applications by that date. I know many growers that may spray once or twice before July 10th or R3 (early pod), but this year may be a good year to start spraying later. My thought process here is that: 1) leaf spot fungicide applications made on young peanuts in the early, vegetative stages are less susceptible to leaf spot; 2) much of the fungicide applied ends up on the soil surface and can’t protect peanuts or be taken up by foliage; and 3) since it seems peanut growth is delayed digging may occur later than normal so fungicide applications may be needed later than normal. If you start spraying now you may increase the number of fungicide applications you end up making, driving up production costs. In fields on rotations of 3 years or less (higher risk of leaf spot), spraying earlier than July 10th may be warranted. The best way to reduce fungicide inputs is by using a spray advisory such as the Virginia Peanut Leaf Spot Advisory available on the Peanut-Cotton InfoNet (https://webipm.ento.vt.edu/cgi-bin/infonet1.cgi) or the Virginia Peanut Hotline at 1-800-795-0700.

Speaking of disease advisories, don’t forget the VSBA (Virginia Sclerotinia Blight Advisory). One thing to make note of with the VSBA is that much of the risk calculated for Sclerotinia blight is based on the vine growth and canopy development of peanuts. So if peanuts are behind in growth the risk of developing Sclerotinia blight is also delayed. Therefore fungicide applications made to prevent Sclerotinia blight should be made later depending on vine growth. I would at least wait until vines are less than 6-inches from meeting in row middles before making a fungicide application specifically for Sclerotinia blight. The Miravis + Elatus tank-mix targets both leaf spot and Sclerotinia blight, so the July 10th start date still applies to the first application of that combination. Keep in mind that if it looks like we may be digging peanuts late that an additional application of Omega 500 may be needed up to 30 days prior to harvest to manage Sclerotinia blight if the second Miravis + Elatus tank-mix is applied in early August. Also, I recommend a FRAC Group 3 or DMI fungicide (like Provost Silver) that’s effective against Sclerotinia blight to go out with the last application of Miravis in case some leaf spot is present at the time of application. FRAC Group 3 or DMI fungicides have some curative or “kick-back” activity which can arrest leaf spot that’s present at the time of application.

The allium leafminer (ALM), Phytomyza gymnostoma (Loew) (Diptera: Agromyzidae), is an invasive fly species that was first recorded in the U.S. in Pennsylvania in 2015. The pest attacks onions, garlic, and leeks where the larvae (maggots) feed on plant tissue by mining the plant causing wilting and possible death. This new pest to the mid-Atlantic area is a long grey-black fly with a distinctive yellow or orange patch on the top of its head, yellow sides and “knees” (femur-tibia junction), and white halteres (knobs as second pair of wings). The larvae are a typical whitish maggot. Adult females repeatedly puncture leaves with their ovipositor, resulting in a line of small white dots. Leaves can be wavy, curled and distorted. Larvae mine leaves and move into bulbs and leaf sheathes where they pupate. This invasive pest was recorded in southwest Virginia in 2021 and has been found in Montgomery, Carroll, Botetourt, and Bedford Counties in Virginia. Please pass this information on to VCE personnel and Master Gardeners so that we can track the spread of this invasive pest in The Commonwealth. The photos below show the life stages of this pest. The egg laying scars (perfect line of tiny circle marks on stems) are telltale sign.

Control: Covering plants in April-May, or September-October, during the adult flights, can exclude the pest. A number of systemic and contact insecticides can provide effective control including neonicotinoids, diamides, spinosyns, and pyrethroids. Products registered for allium leafminer control include:

Mustang Maxx  2.88 to 4.0 fl oz/A           zeta-cypermethrin

Warrior 1.28 to 1.92 fl oz/A         lambda-cyhalothrin

Scorpion 35SL    8.75 to 10.5 fl oz/A         dinotefuran – soil

Scorpion 35SL    5.25 to 7.0 fl oz/A           dinotefuran – foliar

Venom 70SG      5.0 to 6.0 fl oz/A             dinotefuran – soil           

Venom 70SG      3.0 to 4.0 fl oz/A             dinotefuran – foliar        

Entrust SC (OMRI)           3.0 to 6.0 fl oz/A             spinosad           

Radiant SC          6.0 to 10.0 fl oz/A           spinetoram

Trigard 75WSP  2.66 oz/A           cyromazine

Exirel    13.5 to 20.5 fl oz/A         cyantraniliprole

Minecto Pro       7.0 to 10.0 fl oz/A           cyantraniliprole + abamectin

I have had reports of powdery mildew showing up in a few fields lately. Look for white, powdery spots on leaves in the lower canopy. The undersides of leaves can be covered in the powdery growth of the fungus. Cool, humid, dry conditions favor infection, while prolonged periods of cool, humid weather in spring can allow the disease to reach the flag leaf and cause yield losses. If you see powdery mildew in your wheat prior to heading a triazole, such as propiconazole (Tilt and generics) can do the trick, but the earlier the application the better. Fungicides applied at heading for wheat scab are also very effective against powdery mildew.

Wheat is heading and flowering across wheat growing regions in VA. The risk of wheat scab remains low due to dry, windy conditions. No fungicide application is warranted for scab management to crops that are currently flowering or will flower in the next several days. To assess risk of wheat scab, go to the web site https://www.wheatscab.psu.edu

It’s time to be scouting wheat for diseases and Virginia has had favorable conditions for disease development in wheat.  There are really 2 times we should think about spraying wheat: 1) at Feekes Stage 9 (ligule visible on flag leaf); and 2) heading and early flowering (Feekes Stage 10.1 – 10.5).  The spray at Feekes 9 is based on weather conditions and scouting while the Feekes 10.1 – 10.5 application is based on predicted disease risk and stage of flowering.  Feekes 9 applications target powdery mildew, stripe rust, head and stem rust, Stagonospora leaf and glume botch, Septoria leaf blotch, and tan spot.  The sprays at heading and flowering target wheat scab (Fusarium head blight).  Most fungicides are efficacious against the diseases growers would spray for at Feekes 9 but only certain fungicides are recommended for sprays at heading and flowering as they have been shown to reduce the mycotoxin DON that the wheat scab pathogen produces.  Also, strobilurins or FRAC Group 11 fungicides are not recommended for sprays at heading/flowering as these fungicides can actually increase DON levels.  Fungicides recommended for DON are in the table below.

Fungicide efficacy for wheat diseases can be found in the Fungicide Efficacy Table produced by the Crop Protection Network at the following link: https://cropprotectionnetwork.s3.amazonaws.com/fungicide-efficacy-for-control-of-wheat-diseases-filename-2021-04-21-154024.pdf

Scouting for Wheat Diseases:

Begin scouting for wheat diseases around flag leaf emergence (Feekes 8) through Feekes 9 which is when the ligule of the flag leaf is visible.  Be sure to look in different areas of the field, especially where wheat appears further along.

Pictures and descriptions of early wheat diseases are below.

Septoria tritici blotch: Look for elliptical or diamond-shaped, tan-brown lesions that often have yellowish halos. As lesions enlarge the center of the lesion dies and appears dark with small, dark specks which are fruiting bodies that give the lesion a characteristic speckled appearance. Subsequent lesions on higher leaves generally follow leaf veins, having straight edges and no yellow margin or halo.  The dark lesion center and dark speckling is the key to distinguishing Septoria blotch from tan spot or Stagonospora leaf and glume blotch.

Symptoms of Septoria tritici blotch

Tan spot: Tan spot causes light brown or tan lesion with a light tan center that have a distinctive yellow halo (unlike Septoria that has a dark lesion center). Tan spot lesions are more oval than those of  Septoria tritici blotch, but are more angular than Stagonospora leaf blotch lesions.

Symptoms of tan spot

Stagonospora leaf and glume blotch: Foliar symptoms generally begin with small yellow flecks or spots. Spots grow to become lens-shaped lesions that are surrounded by yellow halos.  Lesions are typically longer than those of tan spot but have a dark center like those of Septoria tritici blotch.  However, a yellow halo is often present with Stagonospora and absent with Septoria.  Symptoms on glumes appear as purple blotches or streaks.

Stagonospora leaf blotch symptoms

Powdery mildew: Powdery mildew produces powdery, often fluffy fungal growth on stem and leaf surfaces.  Leaf tissue can turn yellow under the powdery fungal growth.  Signs of this disease typically appear on the lower leaves and work their way up the canopy.  In advanced infections, little black dots can be seen in the fungal growth.

Signs of powdery mildew

Stripe rust: Although stripe rust doesn’t appear every year, when it does appear it can cause losses very rapidly.  For that reason, you need to contact your local county agent or myself if you suspect stripe rust so we can quickly recommend control measures and alert other growers in the area of occurrence.  Like most foliar diseases, strip rust starts out as yellowish flecks on leaves.  From lesions appear yellow-orange, rust-like pustules on susceptible varieties. Pustules on mature leaves occur in parallel lines along the length of the leaf which appears as stripes.

Stripe rust symptoms and signs

Most products in the aforementioned efficacy table are effective against these foliar diseases if applied just before or soon after symptoms appear.

From Daniel Frank (Virginia Tech Pesticides Program):

As of February 28, 2022, all food tolerances for chlorpyrifos were revoked and any new applications of chlorpyrifos will render any food treated as adulterated and ineligible to be distributed in interstate commerce. In issuing the final rule, EPA found that it could not determine that there is a reasonable certainty of no harm from aggregate exposure, including food, drinking water, and residential exposure, to chlorpyrifos, based on currently available data and taking into consideration all currently registered uses for chlorpyrifos. EPA has a dedicated webpage including information for anyone in possession of chlorpyrifos products for use on food when tolerances expire. According to EPA,
• Applicators should discontinue use on food. If the products label allows for use in other non-food settings, it may continue to be used for those non-food purposes.
• Chlorpyrifos products should not be disposed of in landfills for industrial or municipal solid waste.
• Current options for dealing with chlorpyrifos products labeled for use on food:
o Store chlorpyrifos products until there is an opportunity for appropriate disposal. Details on proper storage can be found using the following links:
 https://www.epa.gov/safepestcontrol/storing-pesticides-safely
 https://www.epa.gov/pesticide-worker-safety/requirements-pesticide-storage
o Appropriately dispose of these products as specified by the state.
Information regarding the VDACS pesticide collection program including the 2022 service area and dates/times of collection were previously sent out and are also available here. Should any additional information become available related to the rule including other options for final disposition of the product, I will be sure to share that information.

Regards,

Daniel

—
Daniel L. Frank
Director of Pesticide Programs
Virginia Tech
302 Agnew Hall
460 West Campus Drive
Blacksburg, VA 24061
540-231-3430
vtpp.org

Visit to register: https://go.umd.edu/crop21reg

Due to circumstances beyond our control, we are unable to host the event in-person in 2021. The full program will be offered virtually, with access to programming available to attendees on-demand starting November 15, 2021 through December 10, 2021. The program features speakers from North Carolina State University, Purdue University, University of Arkansas, University of Delaware, University of Maryland, University of Nebraska – Lincoln, University of Wisconsin, USDA-ARS, USDA-NRCS, Virginia Tech, Washington State University, and more.

Registration is $150 for all programing and CCA, pesticide, and nutrient credits. You can register until the December 10, 2021 deadline, but leave enough time to watch the videos! The 2021 Mid-Atlantic Crop Management School will offer CCA continuing education units (CEUs) approved by the Certified Crop Adviser Program in the following categories:

Crop Management (5)

Soil & Water Management (5)

Pest Management (5)

Nutrient Management (5)

State level pesticide and nutrient management credits will be available based on approval of each talk by agency personnel or representatives. The following state credits are available: nutrient management – DE, MD, VA, PA; state pesticide – DE, MD, VA (private and public), PA. Eligibility for CEU’s will be contingent on completion of the provided online verification form by December 10, 2021. Thank you for your continued support of the Mid-Atlantic Crop Management School and we hope to see everyone safely, in-person in 2022! Registration link: https://go.umd.edu/crop21reg.