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.
Allium leafminer larva (photo by Sean Boyle, Virginia Tech)Allium leafminer larva found in Blacksburg, VA in September 2021. (photo by Sean Boyle Virginia Tech)
Oviposition scars by allium leafminer. Photo by Tom Kuhar.
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
Location: Southern Piedmont AREC. We will not be at the main station, but park directly in the field. Look for signs between Blackstone and the main station on Hwy 40/Darvills Road.
Google Maps link to field entrance: https://goo.gl/maps/iKZmYnjx7wM2
Field entrance near: 1200 Darvills Road, Blackstone, VA 23824. GPS is not always accurate. Field entrance between Nottoway Lanes and Military Road.
Continuing Education Credits Approved:
NRCS Conservation Planner: 2.0
DCR Conservation Planner: 2.0
DCR Nutrient Mgmt Planner: 1.0
Certified Crop Advisor: 2.0 (Pest Mgmt)
Please register by texting 540-315-2954 or emailing flessner@vt.edu
Highlights:
View over 100 herbicide plots
Learn about herbicide resistant Palmer amaranth and common ragweed control options
Cover crops for weed control
Harvest weed seed control:
Chaff lining
Redekop Seed Control Unit
Pasture herbicide plots
If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact Michael Flessner at (540-315-2954) during business hours of 8:00 a.m. and 5:00 p.m. to discuss accommodations 5 days prior to the event. *TDD number is (800) 828-1120.
Virginia Cooperative Extension is a partnership of Virginia Tech, Virginia State University, the U.S. Department of Agriculture, and local governments. Its programs and employment are open to all, regardless of age, color, disability, gender, gender identity, gender expression, national origin, political affiliation, race, religion, sexual orientation, genetic information, military status, or any other basis protected by law.
The upcoming weekend rainfall (our meteorologists seem assured that it’ll be widespread) should greatly help parts of Virginia that are short on or getting short of topsoil moisture and position us perfectly for a good start to the soybean growing season.
However, with the rainfall comes cooler soil temperatures. Below are predictions for 4-inch soil moisture and soil temperature over the next 10 days from Orange (one of the coolest parts of Virginia) and Suffolk (one of the warmest parts). As you see, soil temperatures will plummet from relatively warm (>60o) to nearly 50o or less over the weekend. While soybean seed will germinate and emerge in a reasonable amount of time at 60O, germination and emergence will be very slow when temperatures dip below this.
Therefore, heed my suggestion and make sure that you have a good fungicide seed treatment on anything that you are planting now or early next week.
Below is the fungicide efficacy chart from our Pest Management Guide. The main diseases that we need to concern ourselves with are Rhizoctonia and Fusarium sp. If in wet soils, Pythium and Phytophtora sp. could also be a problem with slow-emerging soybean. Be sure to protect a slow-emerging crop with a fungicide containing the active ingredients that provide good to excellent control of the appropriate disease.
Many may have already planted. Some have stopped planting other crops such and peanut and cotton due to cool soils and started planting soybean instead. Regardless, an advantage of soybean is that it tolerates a wide range of planting dates. I’ve found no advantage to planting soybean before May and have seen little yield penalty from planting as late as the first week of June, under most conditions. There are advantages to planting early and planting late, but that is not the subject of this post. Contact me for more detailed discussion on this matter-it will take more that a few comments.
With that said, I’ve always preferred May planting due to less risk of frost damage and slow emergence that is common with earlier planting. Still there are big differences in management when planting in early- versus late-May. Here I’ll review a few of these.
Plant earliest maturing varieties first, then move to later maturing varieties. This will spread risk and harvest dates. We have however observed that early-planting and/or early-maturing varieties work better under productive soils/fields. If planting on poor soils/unproductive fields, later-maturing varieties will extend the growing season and push the critical pod- and seed-filling stages to less stressful times of the year.
Always plant into moisture. But don’t plant more than 1 inch deep when soils are cool or emergence will be delayed substantially. One-half to 3/4 of an inch is adequate. For later planting dates when soils are warm, one can plant as deep as 1.5 inches and get rapid emergence.
If planting into cool soils (usually before mid-May), use a good fungicide seed treatment. It could take 10 days or more for the soybean to emerge; plenty of time for soil-born seedling diseases to attack.
A final plant population of 70 to 100 thousand plants per acre is usually adequate for full-season plantings. This means that 95 to 130 thousand seed per acre is enough, depending on expected emergence. Our research and in other states have observed that less seed is needed with low-yielding fields and greater seeding rates are needed with high-yielding fields. The problem is knowing how much the field will yield.
As always, contact me for more details regarding these tips or discuss other early-season soybean issues.
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.
White, powdery spots. Photo courtesy of Rick Brown.Powdery growth covering underside of leaf. Photo courtesy of Rick Brown.
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.
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
Crop Protection Network: Grau and Burrows
Left is a picture of Septoria blotch showing lesions with dark centers and little to no yellow halo except for new lesions. The right picture illustrates symptoms of larger lesions that have grown together.
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
Crop Protection Network: Burrows
Left is a picture of tan spot lesions that are fairly oval and have tan centers. The right picture demonstrates the characteristic yellow halo caused by 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
Crop Protection Network: Wise
Left are early lesions while the right picture are coalesced lesions in more advanced infections. A distinct yellow halo is almost always present with Stagonospora.
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
Crop Protection Network: Burrows
Left is fluffy fungal growth of powdery mildew on lower stems and leaves. On the right can be seen small, black fruiting bodies in the fungal growth.
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
Crop Protection Network: Burrows and Grau
Very linear sporulation and symptoms of stripe rust on left. Larger, coalesced lesions of stripe rust on right.
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
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.
Nematodes consistently rank as a top yield robber of soybeans. Join us November 16 from 9-12:00 for the Nematode in Atlantic Soybean Production Webinar to discuss nematode distribution and management strategies for the region. The webinar is free, but registration is needed for access to the zoom link. Registration information can be found at https://www.pcsreg.com/nematodes-in-atlantic-soybean-production-webinar. Topics of emphasis will include updates from regional nematode distribution surveys, assessment of soybean cyst nematode seed treatments, root knot nematode on-farm field trials, general management strategies, and how to collect and submit soil samples. Please email Alyssa Koehler akoehler@udel.edu with any questions.
David Langston, Extension Plant Pathologist, Virginia Tech Tidewater AREC
