White Rot of Onion and Garlic

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White Rot of Onion and Garlic

By Jerry Brust, UME and Karen Rane, UMD Plant Diagnostic Lab

One very serious soil disease that affects Allium species, especially onion and garlic, is white rot, caused by the fungus Stromatinia cepivorum (syn. Sclerotium cepivorum (fig. 1)). White rot is NOT the same as white mold, which is caused by Sclerotinia sclerotiorum, which has a very large host range (tomatoes, peppers and 170 other plant species); white rot only infects Allium species.

White rot on base of a garlic plant.
Fig. 1.) White rot on garlic plant. Photo By K. Rane, UMD,

Leaves of Allium plants with white rot exhibit yellowing, dieback, and wilting. Under ideal weather conditions, white mycelial growth can develop on the bulb. As the disease progresses, the mycelium becomes more compacted with numerous small, spherical black bodies (sclerotia) forming on this white mat (fig. 2). These sclerotia are the overwintering structures of the pathogen and are approximately the size of a pin head. As the disease progresses, these sclerotia are eventually released into the soil. Infected plant roots will rot, making the plant easily pulled from the soil. Disease development is favored by cool, moist soil conditions. The soil temperature range for infection is 50°-75°F, with an optimum of 60°- 65°F. At soil temperatures above 78°F, the disease is greatly inhibited. Soil moisture conditions that are favorable for onion and garlic growth are also best for white rot development.

Spherical black bodies a of mycelial growth of the white rot fungus on garlic.
Fig. 2) Sclerotia (Spherical black bodies a of mycelial growth ) of white rot fungus on garlic. Photo By G. Brust, UMD.

An increase of white rot in a field that has had several Allium crops may go unnoticed for a time as sclerotia numbers increase and disperse. One sclerotium per 20 pounds of soil will cause disease and results in measurable crop loss. The sclerotia will lay dormant until root exudates, exclusively from an Allium species, stimulate germination. Root exudates from non-Allium species will not stimulate the germination of white rot sclerotia. Cool weather is needed for both sclerotia germination and mycelia growth. Mycelia will grow through the soil until they encounter an Allium root at which time the fungus initiates infection. Mycelia can grow from one plant to a nearby plant, allowing the pathogen to move between plants.

Management of white rot should focus on disease avoidance by not introducing the pathogen into a field. Sclerotia can spread throughout a field, or from field to field, through the movement of soil, equipment, or plant material (especially garlic cloves). Sanitation is important to prevent sclerotia from moving from an infested field to a clean field. Plant only clean stock from known origins that has no history of white rot. Always clean soil off of equipment and sanitize with quaternary ammonia before moving to another field. The Allium crops from an infested field should not be used as seed. Rotation alone will not control white rot because sclerotia can survive in the soil for 20-40 years. If the disease is found, reducing or eliminating irrigation will reduce the damage to the current crop but will not stop the spread of the disease.

Because the fungus is vulnerable to temperatures above 115°F, dipping seed garlic in hot water is a possible preventive measure that will reduce the amount of pathogen but will not completely eliminate it. Temperature control is important when using this method because temperatures above 120°F may kill the garlic. There are other cultural and organic practices (i.e., biofumigation and solarization) that a grower might try to fight this disease and these can be found at: https://rvpadmin.cce.cornell.edu/uploads/doc_479.pdf

Chemical applications can be made for white rot management and include for onion tebuconazole applied in a 4-6 inch band over or into the furrow at planting or via chemigation. For garlic an in-furrow at-planting application using iprodione or tebuconazole or fludioxonil can reduce disease incidence, however there are crop rotation restrictions with the use of these chemicals so be sure to check the Mid-Atlantic Commercial Production Recommendations guide for more details.

One other note is that the presence of bulb mites can exacerbate disease problems by opening the bulb up to infection from white rot and growers also will need to manage these mites.

Check for Allium Leaf Miner in Onions and Leeks

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Check for Allium Leaf Miner in Onions and Leeks

By Jerry Brust, IPM Vegetable Specialist UME

If you grow leeks or onions or other Allium species, you should already be checking for the tell-tale marks left by Allium leaf miner. Allium leaf miner Phytomyza gymnostoma tell-tale marks consist of many linear small white dots (made by the female’s ovipositor) that appear in the middle towards the end of leaf blades (fig. 1) of their preferred hosts of leeks, onions, garlic and other Allium species. Spring crops are usually not as hard hit as fall crops especially when looking at leeks, but this pest has been steadily increasing its geographical range each year as well as its damage potential. If you had some infestation last year you will especially want to be looking for the signs of this pest.

Image of a Onion leaf blade showing linear white dots made by female Allium leaf miners.
Fig 1.) Onion leaf blade showing linear white dots made by female Allium leaf miners. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org

To go over recommendations for this pest: New transplants or seedings of onions, leeks or garlic should be watched closely for the tell-tale signs of the fly’s damage. When eggs hatch the larvae at first mine leaves (fig. 2) and then move down to the bulbs and leaf sheathes where they feed and eventually pupate. Pupae will undergo a summer aestivation (type of hibernation because temperatures are too warm for them to be active) and only emerge again in late September. You can cover any just-transplanted Allium planting with a row cover (but don’t wait too long after transplanting) to keep the flies off or if needed treat with insecticides. Research out of Cornell University has found using just two applications of spinosad (Entrust, which is OMRI-labelled) two weeks after oviposition marks are first found and then another application 2 weeks after this will give adequate control of the pest. But the oviposition marks must be watched for carefully and discovered very soon after first being made. If new oviposition marks are being seen each week a weekly application of insecticide may be necessary. A penetrant adjuvant also is recommended to be used when treating for the larvae.

Leaf miner damage on a Onion leaf blade caused by the larva of a Allium leaf miners fly.
Fig. 2) Allium leaf miner larva mining in onion. Photo by G. Brust, University of Maryland.

MARYLAND PESTICIDE NEWS UPDATES

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MARYLAND PESTICIDE NEWS UPDATES
(April 2023)

by Niranjana Krishnan,
UMD Pesticide Safety Education Program Coordinator

The express purpose of the newsletter is to share proposed and upcoming changes to pesticide regulations; the information provided does not supersede existing pesticide labels and regulations. If you would like to receive this newsletter or have any questions about it, please email Niranjana Krishnan nkrish@umd.edu 

  1. Forthcoming change: First pesticide tolerance established for hemp 

Summary by Niranjana Krishnan nkrish@umd.edu

In April 2023, the Environmental Protection Agency (EPA) established the first pesticide  tolerance (see glossary) for hemp. This was done for the herbicide ethalfluralin. Specifically, the maximum amount of ethalfluralin residues allowed to remain in or on  hemp seeds was established.  

  • The EPA has accepted ethalfluralin labels that now contain directions for use on  hemp. The new labels will allow farmers to use ethalfluralin to control annual  broadleaf and grassy weeds that grow in hemp fields. Prior to this, only biopesticides  were registered for use on hemp. The biopesticides are tolerance exempt because of  their low risk to humans.  
  • The 2018 Farm Bill removed hemp and hemp seeds from the list of controlled  substances and authorized its production. Consequently, over the last few years, hemp  production has increased in Maryland and other states.  
  • According to the 2020 Maryland Pesticide Use Survey, ~ 122 lbs. of ethalfluralin was used on other crops. 

Reference: https://www.epa.gov/pesticides/epa-establishes-first-pesticide-tolerance hemp   

  1. Proposed change: New health protections to reduce ethylene oxide exposure In April 2023, the EPA proposed changes to ethylene oxide use to reduce air emissions  and protect exposed workers. Ethylene oxide is a gas and, for certain uses, is registered as  an antimicrobial pesticide. It is used to sterilize spices (like dried herbs and vegetables) at  commercial sterilization facilities to control food-borne pathogens. It is also used to  sterilize certain equipment like medical devices. Long-term exposure to ethylene oxide  increases the risk of certain cancers. 
  • To protect workers involved in the sterilization process, EPA is proposing the use of  self-contained breathing apparatus or a supplied airline respirator. Additionally, EPA  is proposing real-time monitoring of ethylene oxide concentrations in the workplace.  If concentrations exceed 10 parts per billion, all workers, including office workers,  will be required to wear a breathing apparatus or respirator to reduce exposure.  
  • To reduce exposure concentrations within commercial sterilization facilities, EPA is  proposing measures such as implementing air pressure gradients to regulate ethylene  oxide flow, separating HVAC systems between office and sterilization areas, 

ventilating ethylene oxide storage areas, automating the transport of sterilized  materials, etc.  

  • To reduce exposure concentrations within healthcare settings, EPA is proposing  lowering the amount of ethylene oxide used per sterilization cycle for medical devices  (lower concentrations will also meet sterility requirements), separating sterilization  spaces from other work areas, implementing air pressure gradients, using abatement  devices to remove ethylene oxide from exhaust air, etc.  
  • Public comments are being sought until June 15, 2023. 

Reference: https://www.epa.gov/newsreleases/epa-proposes-new-standards-protect public-health-reduce-exposure-ethylene-oxide 

  • Update on pesticide testing requirements for PFAS (Maryland-specific) In April 2023, two bills (SB0158 and HB0319) were amended and passed in the  Maryland General Assembly. The bills require the Maryland Department of Agriculture ̶ in consultation with the Maryland Department of Environment, Maryland Department of  Health, and the EPA ̶to study the use of PFAS in pesticides. The bills  originally proposed prohibiting pesticide products from being registered in the state  unless it was tested for PFAS. However, several questions were raised about PFAS  testing methods which resulted in the bills being amended. The bills now require: 
    • An analysis of the health and environmental impacts of PFAS in pesticides in  Maryland 
    • An identification of testing methods capable of testing PFAS in pesticides.
    • An examination of characteristics that distinguish testing methods for PFAS that are  validated for drinking water from testing methods that are validated for pesticides.
    • A status update on federal efforts to certify a method for testing PFAS in pesticides.
    • A status update on state and federal efforts to regulate or ban use of pesticides  containing PFAS. 

The bills take effect on June 1, 2023, and the Maryland Department of Agriculture must  report its findings and recommendations by November 1, 2023.  

References:  

https://mgaleg.maryland.gov/mgawebsite/Legislation/Details/sb0158?ys=2023RS https://mgaleg.maryland.gov/mgawebsite/Legislation/Details/HB0319?ys=2023RS 

Glossary: 

1) Pesticide tolerance – The maximum amount of a specific pesticide that may remain in or  on foods marketed in the United States. The EPA is responsible for setting the tolerances and ensuring they are protective of human health.  

2) PFAS (perfluoroalkyl and polyfluoroalkyl substances) – They are a class of fluorinated  compounds that do not degrade easily and are found in many products and matrices.  Exposure to certain PFAS compounds can adversely affect human health. 

Upcoming Ag Law Webinars

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The Department of Agricultural and Resource Economics (AREC) will host five webinars via zoom every Friday starting on Friday, March 31st, and ending on Friday, April 28th. The free webinars will cover those legal issues that Maryland landowners may face. A grant funds the program through the Northeast Risk Management Education Center. The webinars will feature Paul Goeringer, a Senior Faculty Specialist and Extension Specialist in agricultural law.  He will address leasing, landowner liability issues, right-to-farm law, fencing laws, livestock liability, and estate planning.  As well as additional feature speakers Tim Bishton with Crow Insurance Agency, Stephanie Brophy with Dulany Leahy Curtis & Brophy LLP, and Brooke Schumm with Levin Gann, P.A.

“These webinars will be a great opportunity for landowners and other professionals in rural areas to learn about some of the basic legal issues that many deal with daily.  They can understand their rights and responsibilities whether they are involved in agriculture or own land in a rural area,” said Goeringer.

Each webinar will begin at 12:00 pm and run to 1:30 pm.  The dates and topics are:

  • March 31st- Negligence, Livestock, and Guests on Farmland
  • April 7th- Fencing and Right to Farm
  • April 14- Agricultural Leasing
  • April 21- Understanding Insurance
  • April 28- Working with an Ag Law Attorney

Participants will receive copies of Extension fact sheets and other valuable documents as a part of the workshop series.
For more information, please get in touch with Paul Goeringer at lgoering@umd.edu. This institution is an equal opportunity provider.If you need a reasonable accommodation to participate in any event or activity, please contact Ryan Zimmerman @rzimmer7@umd.edu.

Click here to register

This is material is based upon work supported by USDA/NIFA under Award Number 2021‐70027‐34693.

PRODUCE SAFETY RULE GROWER TRAINING

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The Maryland Food Safety Network will be hosting a hybrid Produce Safety Rule Grower Training on December 7-8, 2022. The training will be delivered over 2 half-day sessions (December 7, 2022 – 1:00 – 5:30 PM, December 8, 2022 – 12:30 – 4:45 PM). Cost $35. Attend online via Zoom or in person at the UMES Research, Education, & Extension Farm (10789 Stewart Neck Rd. Princess Anne, MD)

The training will cover:

  • Role of Maryland Dept. of Agriculture and On-Farm Readiness Reviews
  • Worker Health, Hygiene, and Training
  • Soil Amendments
  • Wildlife, Domesticated Animals, and Land Use
  • Agricultural Water (Part I: Production Water; Part II: Postharvest Water)
  • Postharvest Handling and Sanitation
  • How to Develop a Farm Food Safety Plan

REGISTER ONLINE
https://MFSNproducesafety1222.eventbrite.com

Small Farm and Urban Agriculture Program

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​MDA’s Small Farm and Urban Agriculture ​Program is currently offering Small Farm Cover Crop Program grants. Other grant programs are currently under development.
 
This Program is the first in a series of statewide financial assistance programs to be introduced by the Small Farm and Urban Agriculture Program. It provides needed financial and technical assistance to support small-scale farms located in urban, peri-urban, rural, and suburban areas. Its goal is to increase community access to healthy foods by helping farmers improve their management of natural resources by adopting Bay-friendly and climate-smart farming practices. 
Urban and small-scale producers who may not qualify for traditional cover crop programs are encouraged to apply for these small farm cover crop grants. Here are the program highlights: ​
  • Urban agricultural growers and small farmers who plant five (5) or fewer acres of a cover crop may apply for our cover crop grants.
  • Eligible species to be planted include cover crop seed mixes or single cereal grains. ​
  • Cover crops may be planted in open plots, raised beds, or a high tunnel following the harvest of a production crop (vegetables, herbs, flowers, sorghum, soybeans, hemp, millet, or tobacco).
  • Growers should plant fall cover crops following seed company recommendations, but no later than November 30, 2022.
  • Growers will be reimbursed based on paid receipts with a maximum payment of up to $1,000 per growing season.
  • Please download an application, instructions, and agreement from the right panel.
​FUNDING
This program is funded by the Chesapeake and Atlantic Coastal Bays Trust Fund and managed by the department’s Conservation Grants Program. ​

Sensor Placement and Floating Row Cover Impact on Fruit Rotting Diseases in Strawberries

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Sensor Placement and Floating Row Cover Impact on Fruit Rotting Diseases in Strawberries

Scott D. Cosseboom and Mengjun Hu
Department of Plant Science and Landscape Architecture, University of Maryland College Park

Various sensors can be used to monitor environmental variables in fields, including ambient temperature, relative humidity, rain depth, wind speed, leaf wetness (LWD), soil temperature, and soil moisture. These can be critical variables for decision making for crop protection or yield prediction. These data (namely ambient temperature and LWD) can also be useful for disease prediction models such as those used for Botrytis (BFR) and anthracnose (AFR) fruit rots of strawberry (Hu et al. 2021). A traditionally placed weather station at the edge of a field (see ‘elevated’ station below) may also not fully capture the conditions in the field. Floating row covers are a common tool in Mid-Atlantic strawberry fields for manipulating the crop microclimate for facilitating crop development under cold conditions and for protecting from freeze events. Therefore, covered strawberry plants should have a vastly different microclimate than would be reported from traditionally placed weather stations or non-covered plants. We evaluated differences in sensor readings based on placements either in the canopy or in the traditional, elevated setting. We also evaluated the effect of row covers on the sensor readings. Lastly, we evaluated how these different placements would affect disease prediction models utilized in a fungicide spray program.

Continue reading Sensor Placement and Floating Row Cover Impact on Fruit Rotting Diseases in Strawberries

High Tunnel Grower Should Consider Testing for Soluble Salt

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Emily Zobel, UME; ezobel@umd.edu & Jerry Brust, IPM Vegetable Specialist, UMD; jbrust@umd.edu

If you had plants in high tunnel this season that were showing drought and salt stress in the form of poor growth, thin canopy, excessive leaf drop, poor fruit set, poor yields, necrotic leaf margins, especially on older leaves that can curl, then you might want to consider testing your soil for high soluble salts. These excess soluble salts often come from compost, manure, or fertilizers frequently applied without sufficient water (rain) to leach them through the soil.  

High soluble salt levels in the soil can harm crops via drought stress in several ways. First, they can draw water away from plant roots resulting in wilted foliage and damaged roots (fig. 1). The plant roots can also absorb the excess soluble salts in the soil but cannot metabolize them. The soluble salts enter the roots and are moved through the water-conducting tubes to the leaves, where the water evapotranspires, gradually concentrating the salts to toxic levels. 

Lettuce seedling showing burned rootlets.
Figure 1.) Lettuce seedling showing burned rootlets. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

Some vegetable crops are much more sensitive to soluble salts than others. Crops such as green beans, onions, and peas are the most sensitive, while cabbage, cucumbers, peppers, and potatoes are a bit salt tolerant. Broccoli, squash, and tomato are moderately salt tolerant. 

Some possible remedies for high salts include having adequate drainage to help move salts out of the root zone and flushing the soil with as much water as possible for several days. When doing this, slowly apply the water, so it seeps into the soil and does not runoff. After the season, it may be best to take the plastic off the high tunnel and allow rain and snow to move the salts out of the growing zone, but you need to know if you have high soluble salt levels first, so it’s best to that soil test. 

RMA Offers Virtual Workshops on Improvements to the Whole-Farm Revenue Protection and Micro Farm Insurance Options

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RMA Offers Virtual Workshops on Improvements to the Whole-Farm Revenue Protection and Micro Farm Insurance Options 

The U.S. Department of Agriculture (USDA) is offering virtual workshops on Nov. 15 and Dec. 13 for agricultural producers and stakeholders to learn about the latest updates and improvements to the Whole-Farm Revenue Protection (WFRP) and the Micro Farm insurance options. WFRP and Micro Farm are two of the most comprehensive risk management options available. USDA’s Risk Management Agency (RMA) will announce in-person events later this fall. These insurance options are especially important to specialty crop, organic, urban and direct market producers. Policy improvements and these workshops are part of RMA’s efforts to increase participation in crop insurance.

“We want to make sure farmers and ranchers know about these very important insurance options. We invite specialty crop, organic, urban and direct market producers to join the virtual ‘RMA Roadshow,” RMA Administrator Marcia Bunger said. “The RMA Roadshow will include me and leadership to highlight important improvements to Whole-Farm and Micro Farm and answer your questions.”

Improvements include:

  • Doubling the maximum insurable revenue under WFRP, now up to $17 million
  • More than tripling the size of farm operations eligible for Micro Farm to $350,000 in approved revenue
  • Reducing paperwork requirements for WFRP.

More information can be found on the RMA Road Show website here: https://rma.usda.gov/Topics/Outreach-and-Education/RMA-Roadshow

UMES Small Farm Conference & Mid-Atlantic Crop School

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UMES Extension’s 19TH Annual Small Farm Conference will be held in-person on the UMES campus, on November 4-5, 2022. The main objective of this two-day event is to equip farmers and landowners in Maryland and along the Delmarva Peninsula with tools and strategies to increase farm profitability and promote farm sustainability. Registration is $70 for both days or $35 for only one day. More information and registration can be found here: https://wwwcp.umes.edu/extension/small-farms-program/conference/

The Mid-Atlantic Crop Management School well be in-person in Ocean City, MD on November 15-17, 2022. Registration is $325 until October 15 and will increase to $375 until registration closes at midnight on November 7th.The Princess Royale will have discounted room rate till avaible till October 14th. More information and registration can be found here: https://go.umd.edu/crop22registration.