Vegetable Notes 2025 Vol. 37:4

Thank You to Our 2025 Sponsors!

 

 

 

Crop Conditions

Cool conditions continue, with more rain and a few freezing nights in the past week, and the forecast continues to be on the cool side. Hardiness zones in MA range from 5b in the Berkshires to 7b on the Cape and Islands with last spring freeze dates of May 5 to April 5, respectively. It is very tempting to jump the gun and plant before those dates, but year after year we see that the plants that go out into cold soils have decreased yields (see research from corn and soybean systems). Low temperatures and gray skies slow plant growth considerably, so resist the temptation unless you can keep the crop covered with remay and/or plant in heated greenhouses or high tunnels. 

More immediately, folks are antsy to get fields turned over and prepped for planting, but some soils may still be too wet—resist the urge to work wet soil! Tilling or planting in wet soils can cause any of the following problems:

Compaction: Wet soils are very susceptible to compaction, as the saturated soil loses its structure and cannot hold up to the weight of heavy equipment (or animals). Tillage equipment also always creates subsurface compaction layers: disks or field cultivators close to the soil surface and moldboard plowing at deeper depths. Tillage in wet soil conditions only worsens the effects of tillage pan or plow layers. The resulting layer will restrict water movement and root growth,  preventing plants from accessing nutrients and moisture.

Clods: Plowing wet soil creates irregular clumps of soil that are hard to break up even once dry, requiring extra tillage passes to create an adequate seeding or planting bed. To avoid clods, use shallower and narrower shanks or disks. Wings and twisted or parabolic shanks are more likely to create clods, and moldboard plowing creates the most clods.

Planter sidewall compaction/smearing: In wet soils the openers on a planter “smear” the sides of the furrow, creating a compacted layer of soil that restricts outward root growth. 

Assess field moisture first: Dig a soil sample 1” deeper than your intended tillage depth. Roll the soil between your hands into a log or worm. If the roll is 5” long without breaking up it is too wet. Alternatively, roll the soil into a ball—if it leaves a muddy mess on your hands it is too wet. If you drop the ball on the ground and it does not break apart it is too wet. Here is a guide to visually assess soil moisture by texture.

If you must: Use a light pass with a disk set at 3” to incorporate any residues or knock back winter annual weeds and introduce some air into the surface layers of the soil. 

Contact Us

Contact the UMass Extension Vegetable Program with your farm-related questions, any time of the year. We always do our best to respond to all inquiries.

Vegetable Program: 413-577-3976, umassveg[at]umass[dot]edu (umassveg[at]umass[dot]edu)

Staff Directory: https://ag.umass.edu/vegetable/faculty-staff

Home Gardeners: Please contact the UMass GreenInfo Help Line with home gardening and homesteading questions, at greeninfo[at]umext[dot]umass[dot]edu (greeninfo[at]umext[dot]umass[dot]edu).

Pest Alerts

Alliums

Allium leafminer typically emerges in mid-April, around 350 GDD base 1C. Currently we are about 60 GDD behind where we were this time last year, so we may expect a later emergence of this pest this spring. That said, in order to prevent damage crops should be covered with remay or insect exclusion netting before the adult flying and egg-laying begin or be prepared to use an insecticide once egg laying begins in your area.

Asparagus

Prevent weedy fields by acting now! See the article in this issue for details.

Brassicas

Flea beetles emerge in April in many years so be prepared by covering crops with remay or insect exclusion netting, or be prepared to use an insecticide to prevent damage to greens and heading crops which can be severely stunted by early feeding.

Multiple/Miscellaneous Crops

Damping off is common in greenhouses this time of year and we have seen outbreaks across the region. Caused by several different soil-dwelling fungi and oomycetes which infect plant seeds and roots, this disease leads to failed germination or wilt and even dieback of seedlings. The pathogens that cause these symptoms are weak, and cannot infect healthy, full-grown plants. Avoid conditions that favor damping off by: not overwatering; choosing a small cell-size so soil dries out more quickly; allowing seedlings to dry between watering; using lighter media and/or a misting wand; and promoting rapid plant growth by using strong seed and ensuring the house is adequately warm. Sanitation is also key, as these pathogens survive on trays and benches, in soil, dust, and weedy patches in the house. See the transplant production section of the New England Vegetable Management Guide for a table of fungicides labeled for use on vegetable seedlings indoors and look for those with damping off on the label. Preventive applications are most effective.

Fungus gnats and shore flies are another common sight in spring greenhouses. These flies lay eggs in damp soils with high organic matter, and their larvae primarily feed on the fungi and algae that thrive in these soils. However, fungus gnat larvae may also feed on plant roots when populations are high, causing direct damage to seedlings and allowing pathogens to attack weakened roots. High pest densities are typically a symptom of overwatering or the presence of soil or algae on greenhouse surfaces and can be remedied by eliminating these breeding sites. Several biological control agents are available for fungus gnat control, including a predaceous mite (Hypoaspis miles), a parasitic nematode (Steinernema feltiae), and a rove beetle (Dalotia coriaria). Insecticides targeting fungus gnats should be directed toward the larval stage at the first sign of activity, and should be applied to a depth of 1” or more. Repeated applications may be necessary and are most effective when retained in the media. 

Spring Asparagus Weed Management

Weed management in asparagus can be challenging for several reasons. Asparagus spears are harvested before any fern development, so there is no crop canopy until late into the growing season¹. Cultivation to manage weeds is possible but needs to be done carefully to avoid injuring roots of this perennial crop. The whole field can be cultivated early in the spring, but if not timed accurately, growers risk damaging underground spears and delaying harvest by several weeks^1,2. Early spring tillage helps to control winter annual weeds, but can stimulate the germination of summer annual weeds, so often is not effective on its own¹. Several cover crop and living mulch systems have been explored in asparagus. Cover crops are useful when seeded in the fall to help suppress winter annual weeds³, but living cover during the summer reduces yield². Herbicides are therefore a critical weed management tool for most asparagus producers, especially in targeting summer annual and perennial weeds^4,5.

Right now, before spears emerge from the soil, is an important time to apply pre-emergent herbicides⁶. See Table 1 for a list of labeled pre-emergent herbicide options for asparagus. When selecting the right herbicide for your farm:

• Choose products to target the summer annual weeds in your field.
• Be sure to rotate through Modes of Action (MOA) from year to year to reduce the development of herbicide resistant weeds⁵. The Herbicide Resistance Action Committee (HRAC) has created a globally harmonized system to classify herbicides based on their MOA. Using herbicides with different HRAC numbers ensures that you are appropriately rotating MOAs.
• Rotating herbicides will also reduce any potential damage to asparagus. There is some evidence that repeated use of flumioxazin in sandy soil can lead to spear damage⁵.

HRAC: Globally harmonized classification based on the herbicide mode of action, set by the Herbicide Resistance Action Committee

* Also has post-emergent activity on weeds

--Written by Maria Gannet, UMass Extension Weeds Specialist

1. Boydston, R. A. Effect of Tillage Level and Herbicides on Weed Control and Yield of Asparagus ( Asparagus officinalis ) in the Pacific Northwest. Weed Technol. 9, 768–772 (1995).
2. Paine, L., Harrison, H. & Newenhouse, A. Establishment of Asparagus with Living Mulch. J. Prod. Agric. 8, 35–40 (1995).
3. Brainard, D. C., Bakker, J., Noyes, D. C. & Myers, N. Rye Living Mulch Effects on Soil Moisture and Weeds in Asparagus. HortScience 47, 58–63 (2012).
4. A. G. Ogg, Jr. Control of Canada Thistle and Field Bindweed in Asparagus. Weed Sci. 23, 458–461 (1975).
5. Zandstra, B. H., Morse, S., Tocco, R. V. & Morrice, J. J. Response of Asparagus to Repeated Application of Residual Herbicides. HortTechnology 23, 109–113 (2013).
6. Martelloni, L. et al. A combined flamer-cultivator for weed control during the harvesting season of asparagus green spears. Span. J. Agric. Res. 15, 5 (2017).

Pre-emergent Herbicides

As you start to think about planting crops, you will also need to start thinking about managing weeds. Crop establishment is an important time to manage weeds and one tool that can really help during that establishment phase is a pre-emergent herbicide. Let’s do a little pre-emergent herbicide review.

Pre-emergent herbicides, as the name suggests, are herbicides that kill weeds before they have emerged from the soil. Pre-emergent does not refer to the crop; they can sometimes be applied after the crop has emerged. Specific application timings for each crop will be listed on the label. Pre-emergent herbicides can also be called residual herbicides because they remain active in the soil for a period of time and can thus control germinating weeds long after application. Several herbicides can kill weeds whether they are applied pre-emergent or post-emergent, but for the sake of this review, let’s just focus on pre-emergent applications.

Considerations for applying a pre-emergent herbicide

When you apply pre-emergent herbicides there are several details you should take note of to get the best control.

• The application rate will be based on your soil’s organic matter content and texture. Make sure to adjust your rate accordingly so that you achieve good control without damaging your crop.
• Since you are targeting seeds that are germinating within the soil profile, you need to move the product down into the zone of germination with water (irrigation or rainfall work) or tillage. Make sure this is done within the length of time specified on the label. UV light will degrade product left for too long on the soil surface.
• You usually need adequate soil moisture to move the product from the soil into the germinating seed. Many of these pre-emergent herbicides are systemic, not contact, so they need to enter the germinating seedling.
• To get the best coverage, you typically want the soil to be free of other vegetation (dead or alive) when you apply these herbicides. If you have living weeds at the time of application, you can either till the weeds into the soil first or include a burn-down herbicide as a tank-mix. Tank-mixing a burn-down and pre-emergent herbicide will control the aboveground growth while simultaneously achieving residual control with the pre-emergent herbicide.
• There are exceptions to almost all of the above “rules” so always be sure to read and understand the label of the product you are using.

When to apply a pre-emergent herbicide

Figuring out when to apply pre-emergent herbicides can be a little tricky because the words used to describe the application timings are similar and sometimes the same as pre-emergent and post-emergent (which, again, refers to the emergence of weeds and not of crops). The labels will describe when it is safe to apply pre-emergent herbicides for each specific crop. Often, this interacts with how the crop is planted, so there may be specifications for the seeding or plug planting depth to ensure that the crop is not affected by the pre-emergent herbicide. Here is a glossary of different application timings that you might see in a label.

• Preplant incorporated: The pre-emergent herbicide is applied to the soil and incorporated into the soil either by cultivation or water before planting.
• Preplant surface: The pre-emergent herbicide is applied to the soil before planting and needs to be incorporated with water because it is a low- or no-till system.
• Surface incorporated: The pre-emergent herbicide is applied to the soil under established trees or ground areas between trees and needs to be incorporated with water or very shallow cultivation to not disturb the crop roots.
• Premergence (postplant treatment): The pre-emergent herbicide is applied during planting or after the crop seed is planted but not yet emerged and needs to be incorporated with water or very shallow cultivation to not disturb the crop seed.
• Post-transplant: The pre-emergent herbicide is applied after the crop is transplanted.
• At layby: The pre-emergent herbicide is applied at the last cultivation event, just as the crop canopy closes.
• Postemergence (directed or incorporated): The pre-emergent herbicide is applied to the soil under direct-seeded crops that are well established or transplanted crops. Usually the safe growth stage of the crop is specified. The herbicide needs to be incorporated with water or with careful cultivation. *This term is frustrating because the label is referring to the application of pre-emergent herbicides and specifies that emerged weeds will not be controlled, but uses the word post-emergence when describing application timing.

Selecting a pre-emergent herbicide

Selecting an appropriate pre-emergent herbicide can also be tricky. The product you choose should target the weeds in your field, but you will not be able to see the weeds because they will still be in seed form. Instead, you will need to know the species that you have on your farm from weed identification last year. Consider creating a weed map of your farm – it will help your weed management several ways:

• Remembering species
• Encouraging you to identify unknown species
• Keeping track of the spread of species

If you already have a weed map, refer to it to see what species you will be targeting with a pre-emergent application. With these weeds in mind, you will often find that no single pre-emergent herbicide will control all the species. Consider tank-mixing two products to get a wider spectrum of control. Labels will often include a list of compatible products, but you can also do a jar test (check out this article to read more about tank-mix compatibility considerations).

The length of residual control

After you make a pre-emergent herbicide application, you will have residual control for some length of time. Unfortunately, the length of time is based on many factors and somewhat difficult to predict. These factors include:

• The product. Different products have different lengths of activity even when all other factors are equal.
• The rate applied. The rate you apply will be based on your soil texture and organic matter content as specified in the label. But all other factors being equal, higher rates will have longer residual activity.
• The soil environment. Microbes are largely responsible for degrading residual herbicides within the soil profile. Microbial activity is highly dependent on the soil environment, especially pH, temperature, moisture, and organic matter content.

These factors interact and change from year to year so it can be difficult to predict the length of residual activity on your farm, but it will be somewhere between 4-12 weeks. Both the high and low ends of that spectrum are less common. You also need to be careful not to disturb the soil in a way that will change its efficacy. Tillage can expose untreated soil, allowing weed seedlings to emerge unharmed. Alternatively, mounding the soil can effectively double the application rate and cause subsequent crop damage.

No matter how long your residual control may be, it will not last the entire season, so you will need to have a plan to continue managing weeds after any pre-emergent application. But a pre-emergent herbicide can help your crop get a good head start over weeds.

--Written by Maria Gannet, UMass Extension Weeds Specialist

Agricultural Water Part 1:  Understanding FSMA Rules and Assessing Food Safety Risks

This article describes the importance of managing agricultural water to reduce food safety risks and gives an overview of the current water-related requirements under the FSMA Produce Safety Rule. The first compliance date for the new FSMA rule for preharvest water was this week. This is the first in a 3-part series about agricultural water. 

Water and Produce Safety

Water that’s likely to contact produce or a food contact surface may contribute to food safety risks on a farm. Fecal pathogens, including those that are commonly linked to foodborne illness outbreaks, such as Salmonella, Listeria monocytogenes, and pathogenic E. coli, can survive in water for long periods of time and can be moved by water onto various surfaces on a farm, including onto fresh produce. Contaminated irrigation water was implicated in several recent outbreaks of foodborne illnesses, including of Salmonella on whole red onions and E. coli O157:H7 on head lettuce.

Extreme weather events and the warming temperatures we’re seeing in the Northeast may exacerbate water quality issues. Microbial pathogens survive and are spread in fecal matter. Under drought conditions, animals may be more drawn to farm water sources if other sources are depleted and growers may be forced to use lower-quality water. On the other hand, flooding may wash fecal matter into water sources or churn up sediment that contains pathogens. Warmer temperatures increase microbial growth.

Because water is used in so many farm activities, both pre- and postharvest, water quality and managing the sources of fecal contamination of water in the farm landscape are big focus areas for food safety rules and programs.

Growers should routinely assess whether any water they’re using is likely to contain pathogens that might contaminate produce and should use practices that help to reduce the chances that contamination will get onto food. For growers subject to inspection under the Food Safety Modernization Act (FSMA) Produce Safety Rule, there are specific activities and records required to guide this assessment. Similarly, growers who participate in an audit program, such as Massachusetts’ state program, Commonwealth Quality, will have to comply with program rules, which may be stricter than FSMA requirements. 

The FSMA water rule

The Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) requires that “all agricultural water must be safe and of adequate sanitary quality for its intended use”. It defines agricultural water as water that is intended to, or is likely to, contact any fresh produce subject to the rule, as well as any food contact surfaces. All PSR requirements, including those related to water, are final as of last year. The provisions related to preharvest water were pending until they were finalized last December and the first compliance date (for farms grossing over $500,000 a year) was  April 7th, 2025—this week! These growers will have to start having their records available for inspectors this year, though for the first year, inspectors are likely to take a more educational approach in order to familiarize growers with expectations. Smaller businesses will have an additional 1 or 2 years to comply. See here for a summary of compliance dates and requirements.

For recordkeeping purposes, it’s helpful to break the FSMA requirements down into 3 areas:

1. All agricultural water – Applies across the whole system
2. Preharvest water – Irrigation, crop sprays, frost protection
3. Postharvest water – Produce washing, handwashing, cleaning and sanitizing

1. All Agricultural Water

The PSR requires that, at the beginning of the growing season and at least once a year, growers inspect all agricultural water systems to identify produce safety hazards. The system must also be maintained to prevent contamination. Remember, the goal is to prevent fecal matter (which may contain foodborne pathogens) from getting into the water. For some water sources, such as ponds or brooks, it’s inevitable that animals—and their poop—will be in and near the water. The purpose of a routine inspection is to understand where the risks of contamination are and to the extent that it’s within your control, maintain the system to minimize these risks. 

It’s helpful to start with a map of your farm and the water distribution system so you can visualize all of the components of the system from source to outlet (Fig. 1). At least annually, go out and look at all of the components. Some things to look for or to note in your inspection record are below. (Many of these points came from a nice video from MSU Extension on doing a water system inspection.)

• The nature of each water source (i.e., is it ground, surface, or town water?)
• The extent of your control, degree of protection, adjacent land uses, likelihood of introduction of hazards
• Water sources are free of debris, trash, domestic animals, other possible sources of contamination
• Pressure sensors are working
• Check valves are functioning properly
• Well heads are locked
• Conduit pipe is present and secure enough to prevent access to insects and other animals
• Vent holes are screened
• Concrete pads are intact
• Equipment is stored to prevent contamination by animals

Finally, complete a water system inspection record. There is no specific format required for this record under FSMA rules, but a good template is in the Produce Safety Alliance’s document, Records Required by the FSMA Produce Safety Rule (see page 9) (Fig. 2).

2. Preharvest Water

The Rule requires that growers complete a written Agricultural Water Assessment at least annually at the beginning of the growing season and whenever there is a significant change that may impact risk. This assessment is different from the inspection in that it is only required for preharvest water and it requires consideration of some other factors beyond the components of the water system. The assessment must identify conditions that are reasonably likely to introduce known or reasonably foreseeable hazards onto covered produce or food contact surfaces. There are 5 factors that need to be considered in an Ag Water Assessment:

1. The Ag Water System – This is based on your system inspection and includes details about the source and location of the water and how protected it is from contamination.
2. Ag Water Practices – How do you use the water? In overhead or drip irrigation? In crop sprays? How close to harvest do you apply the water? Risk tends to be lower when water is not applied directly to the crop or when the time period between water application and crop harvest is longer.
3. Crop Characteristics – What crops are you applying the water to? Some crops have structures or surfaces that are rough or have crevices that may make them more susceptible to adhesion by pathogens, e.g., leafy greens, or cantaloupe.
4. Environmental Conditions – Consider both typical environmental conditions at times when water is applied, as well as extreme weather events such as drought or flooding, or hail or wind storms that might damage crops and make them more hospitable to bacterial growth.
5. Other factors – The rule allows for other risk factors to be included in the assessment, including the results of water tests. Note that while the previous version of the Produce Safety Rule required growers to take a series of water tests for generic E. coli (an indicator of fecal contamination), the current rule does not require testing, though test results can still be a useful tool to include in an assessment.

If after conducting the assessment, you determine that the water is not safe or of adequate sanitary quality, you must stop using it and correct the issue before continuing use. If the water isn’t necessarily unsafe to use but there are conditions that may introduce risk, you must use mitigation measures to attempt to address them. If the risk is specifically related to animal activity, animal-based amendments, or human waste, it must be corrected promptly and no later than the same growing season. Mitigation measures might include making repairs to the system, changing how the water is applied (e.g., switching to drip irrigation), increasing the time between application and harvest, or if appropriate, treating the water to kill pathogens. 

An Ag Water Assessment is not required for water obtained from a public water system, as long as its quality is not likely to change before use (e.g., it’s not stored in an open cistern or otherwise exposed to contamination after it reaches the farm), or if it meets the standards for postharvest water (see next section). 

There are a few tools available to help guide an assessment, including the FDA’s Ag Water Assessment Builder, and the Risk Prioritization Tool developed by Michigan and Minnesota Extensions. 

Again, there is no specific format required but a good template for an Ag Water Assessment record is available in the Produce Safety Alliance’s document, Records Required by the FSMA Produce Safety Rule (see pages 10-11)(Fig. 3). Additional records may be required if testing is conducted or if mitigation measures, such as system repairs or treatment of the water with an appropriate sanitizer, are taken following an assessment—a list of possible additional records is also included in the template linked above. 

3. Postharvest Water

Requirements for postharvest water have not changed since the Produce Safety Rule was first published and growers are expected to already be in compliance with this part of the Rule. 

Water used in postharvest activities, that is, water used for produce cooling or rinsing, cleaning or sanitizing of food contact surfaces, handwashing, ice making, or any other direct contact with produce or food contact surfaces, must meet the following requirements:

• If untreated ground water – test for generic E. coli 4 or more times during the growing season or over the period of a year. Take 1 or more tests per year after initial year.
• If public water supply – obtain copy of test results or compliance certificate from municipality
• Untreated surface water cannot be used for postharvest activities
• Must have a plan for maintaining and monitoring the quality of recirculated and batch water

The records required for postharvest water are: 

• The results of water tests if using untreated ground water, or
• The compliance certificate if using municipal water and,
• If using sanitizer in produce wash water, any sanitizer treatment monitoring logs. 

State Requirements

The FSMA PSR is a federal regulation that sets minimum food safety standards for fresh produce farms. It is overseen by FDA but generally enforced by state regulatory agencies. In Massachusetts, the Department of Agricultural Resources (MDAR) Produce Safety Team conducts PSR inspections. Many states also have their own voluntary audit programs that provide additional benefits including greater access to educational support or grants and the ability to receive a compliance certificate and use of program branding after a successful audit. They may also have stricter requirements than the minimums set by the FSMA PSR. The Massachusetts Commonwealth Quality Program (CQP)—also implemented by the MDAR Produce Safety Team—is the state’s audit program. Its compliance criteria adhere to the PSR but also include some additional requirements. With respect to preharvest water, growers who choose to participate in CQP must:

• Test each surface water source 3x per year for generic E.coli
• Test each ground water source 2x per year for generic E.coli
• Obtain a quality compliance certificate for municipal water sources
• Meet the threshold for water tests of 126 CFU generic E. coli/100 ml water sample

For a summary of audit program requirements in the 6 New England states, see New England Food Safety Audit Program Water Requirements. 

Conclusion

Regardless of whether you need to comply with FSMA or CQP requirements, you should consider whether any water you use on your farm is likely to contribute to the spread of foodborne pathogens to fresh produce and use measures to mitigate the risks you find. 

In Ag Water part 2, we’ll share results from a recent water quality survey of ag water sources in Massachusetts conducted by UMass Extension and MDAR, and in part 3, we’ll share some tips on finding and working with a water testing lab to get results that can be used as part of a water quality assessment. 

--Written by Lisa McKeag, UMass Extension

News

Events

Vegetable Notes. Maria Gannett, Genevieve Higgins, Lisa McKeag, Susan Scheufele, Alireza Shokoohi, and Hannah Whitehead, co-editors. All photos in this publication are credited to the UMass Extension Vegetable Program unless otherwise noted.

Where trade names or commercial products are used, no company or product endorsement is implied or intended. Always read the label before using any pesticide. The label is the legal document for product use. Disregard any information in this newsletter if it is in conflict with the label.

The University of Massachusetts Extension is an equal opportunity provider and employer, United States Department of Agriculture cooperating. Contact your local Extension office for information on disability accommodations. Contact the State Center Directors Office if you have concerns related to discrimination, 413-545-4800.