Water Testing Requirements

Learn more about water testing requirements on your farm under the Food Safety Modernization Act Produce Safety Rule (FSMA:PSR) for 2024. Rutgers Cooperative Extension has developed a user-friendly survey tool to help you determine if your farm falls under the FSMA PSR. Click here for more information.

Foliar Diseases in Winter and Early Spring Leafy Greens

By Elisabeth Hodgson, ENYCHP, Edited by T. Rusinek ENYCHP

Several diseases commonly affect leaves of winter greens in the Northeast including powdery mildew on lettuce, Cladosporium leaf spot on spinach, and downy mildew on spinach. Other diseases are powdery mildew of brassicas, downy mildew of lettuce, and downy mildew of brassicas.

Alt Text:

Left Photo: Dark Downy Mildew spores develop on undersides of spinach leaves

Middle Photo: Chlorotic yellow spots on the upper surface of lettuce leaf

Right Photo: White Downy Mildew sporulation on underside of lettuce leaf

Photo Credits: Teresa Rusinek

Managing these diseases successfully can be challenging because there is a very low tolerance for disease symptoms on fresh greens. Thus, preventive practices are especially important. With crops already planted this year, the following full management list includes a few practices to implement next season. The key now is to be checking crops for symptoms and reducing humidity and leaf wetness because moisture is favorable for disease development.

⦁Select spinach varieties with resistance to as many races as possible, in particular 12, 14, and 15 which have been detected in the region in the past. 19 races have been identified to date. Varieties do not have resistance to all races, so select multiple varieties to obtain complete resistance for the planting and ensure some spinach remains healthy. Race-specific resistance is highly effective but only to the specified races. Please report when you see spinach downy mildew and the varieties affected to an extension specialist. We are keeping track of races occurring to be able to keep growers informed of what varieties to grow.

⦁ Treat spinach seed with hot-water or bleach for Cladosporium leaf spot. This is not effective for downy mildew pathogens because their oospores are resilient.

⦁ Rotate where crops are grown.

⦁ Use drip irrigation if possible.

⦁ With overhead irrigation, wait until foliage has dried before putting row covers back on.

⦁ Use ventilation and heat to reduce moisture.

⦁ Control weeds which can add to humidity. Some could be harboring powdery mildew fungi.

⦁ Routinely inspect crops thoroughly for symptoms.

⦁ When symptoms are found at a low level, especially when in one area or variety, consider removing plants and marketing leaves that are symptomless to minimize spread and loss. Pathogen spores are dispersed in air currents, therefore turn off fans and minimally disturb plants while removing them to minimize dislodging spores and put plants in a bag rather than a box to take out of the tunnel. Note that there is at least a week from infection until symptoms appear, likely much longer under cool temperatures, so the amount of diseased tissue is greater than is visible.

⦁ Note that the mildew pathogens (downy and powdery) are specific to these crops, so for example, seeing powdery mildew on lettuce in a tunnel is not a potential source of the pathogen for kale being grown there; however, it is an indication that conditions are favorable generally for powdery mildew fungi.

⦁ There are biopesticides and other organic fungicides labeled for many of these diseases that are also labeled for use in greenhouses/high tunnels. They may contribute to control when applied preventively (so best used on a farm where the disease has occurred in the past), on a regular basis (every 7-14 days), and in a way to maximize spray coverage on both leaf surfaces. For crops not managed organically, apply labeled fungicides preventively or at first symptom. Several conventional fungicides are permitted for use in greenhouses/high tunnels on specific crops and for specific diseases. Check REI and PHI when selecting conventional or organic fungicides to make sure it fits your production schedule. Detailed information on management with fungicides can be found here.

⦁ Promptly destroy crops as soon as they are deemed too affected by disease to be salvageable. Best to physically remove affected plants from tunnel to minimize crop debris and pathogen left there.

Images plus additional information about these and other diseases including their management in winter greens are posted here.

Ways To Optimize High Tunnel Production

Vern Grubinger, University of Vermont Extension

(Source: Vermont Vegetable and Berry Grower News, January 6, 2022)

High tunnel systems vary a lot – from super simple to all the bells and whistles – depending on grower goals, crops, finances, etc. so it’s hard to make one list of improvements that fits everyone’s situation. Maybe you’ve done all these things, or maybe you don’t need to. Hopefully there’s something in the list below that’s helpful to your high tunnel management in the coming year!

1. Replace greenhouse plastic before it’s too old. Most greenhouse plastic is rated for 4 years of use. Although they may hold up longer than that physically, all plastic films lose light transmission capabilities over time. Even with UV stabilizers that slow degradation, dust, dirt, and air pollutant accumulation can reduce light available to crops for photosynthesis. Tests of UV-stabilized plastic covering on a multi-bay greenhouse revealed a 6.8% reduction in transmission in Photosynthetically Active Radiation (PAR) after 4 years. Using a PAR meter, or quantum sensor, I have observed this on farms myself. The difference in PAR transmission between old and new covers is more important to crop growth when sunlight is limited, as it is early in the season, or on cloudy days.

2. Optimize roll up sides. Back in the day, a piece of pipe was how most sidewall plastic was rolled up. Today, there are many easier and safer methods available that use geared systems powered by hand or electricity. There are also automated systems that use sensors to raise and lower the sidewalls depending on environmental conditions. These are not inexpensive but growers I’ve talked to say they help optimize crop growing conditions by avoiding exposure to hot/cold temperatures when someone is not available to change the sidewall opening, and they offer some peace of mind if you’re away from the farm when the weather changes significantly.

3. Add drip lines if needed to wet the entire root zone. The extent to which irrigation water moves sideways in soil after it is applied depends on capillary movement. Capillary movement is enhanced by clay and organic matter content of soil. So if your soil is on the sandy side then there may be large dry areas between your irrigation lines if they are widely spaced. That can limit root growth and prevent plants from taking up nutrients even though they were applied. Adding extra drip lines is a low-cost way to make sure that water is distributed uniformly across the entire tunnel growing area. Set up irrigation timers, even inexpensive ones can help provide a consistent water supply.

4. Improve ventilation: add a ridge vent or install hinged gable vents in endwalls. Good ventilation not only provides a consistent supply of fresh air and thus CO2 for plant growth, it’s also critical to managing humidity which can shut down photosynthesis if it’s too high, as well as promote foliar plant diseases. Ridge vents are very effective and promoting air flow and ventilation in high tunnels, though they are not inexpensive, and I hear growers complain about changing the plastic with them. A lower cost alternative, albeit with less impact on air flow, is to install large openings near the top of tunnel endwalls, or gable vents. These can be hinged to open inward, or in “butterfly” fashion. Outward openings are more susceptible to wind damage. Typically, rope and pulley systems are used to operate gable vents.

5. Improve air circulation with HAF fans. Air circulation is not the same as ventilation. Circulation mixes internal air, reducing gradients in temperature, humidity, and CO2 that may be present. Ventilation without circulation can lead to corners or other areas of a tunnel not having sufficient air exchange. Properly installed horizontal air flow fans are a good investment in many high tunnels. Small, 1/10 to 1/15 hp HAF fans with permanent split capacitor motors work well. They move more air yet use less electricity than cheap box fans with shaded pole motors that are often seen in high tunnels.

6. Size ventilation and circulation systems properly. Ventilation flow rates are expressed as cubic feet per minute per square foot of growing area. Good mechanical ventilation requires the right size fans and/or openings. With passive ventilation it’s just openings. An old article by John Bartok, former UConn Extension Ag Engineer, states that roof vent areas should equal the combined sidewall vent area, and each should be at least 15% of the floor area. That seems like a lot, and it suggests that many high tunnels have insufficient passive ventilation. Guidance for circulation flow rates is 25% of the overall growing volume per minute. See Chris Callahan’s blog post on greenhouse ventilation for a summary of how to size these systems.

7. Thoroughly mix soil to re-distribute salts that have moved up to the surface. A SARE-funded research project conducted by UMaine, UNH, and UVM found that during winter months, high tunnel soil can became strongly stratified in terms of soluble salt levels. In two test sites, there was a 10-fold difference in soluble salts between measurements from the top inch of soil vs. a sample 2-3 inches deep. This has implications in terms of soil sampling and seed germination. Although no-till has many upsides, it may not be appropriate in tunnels. Mix your tunnel soil well before testing it or sowing crops.

8. Soil test well in advance of planting seeds and transplants. For in-ground vegetable production we recommend the use of both the saturated media extract (SME) and the regular field soil test (modified Morgan’s extract) to assess the levels of soluble and reserve nutrients, respectively. The UMaine Testing lab offers a “combined high tunnel package” for $30 that includes both tests. SME also measures soluble salts and soluble forms of nitrogen. The SME was developed as a potting soil test, it should be used to test your potting soil mixes well in advance of planting to avoid problems. The cost is $18 at UMaine, and many other labs also offer this test.

9. Apply plenty of K but avoid fertilizers with large granules. High tunnel tomatoes are heavy consumers of K, such that 500-600 lbs./acre of applied K minimized yellow shoulder and maximized yields. Sources of potassium sulfate, a common tunnel fertilizer, vary widely in particle size, and this, in turn affects solubility and release rate. This study found that when a fertilizer with very large particles (several mm diameter) was applied, some large particles were still intact 2 years after application. These would not be available for plant uptake despite being measured by soil tests. Thus when incorporating fertilizers like potassium sulfate, it is advisable to use “fines” that are formulated for more rapid solubility.

10. Test your irrigation water. In the high tunnel, irrigation is the only source of water whereas for crops grown outside, irrigation water is diluted by rainfall. It makes sense to test your tunnel irrigation water to optimize yields and to avoid potential toxicity issues. Penn State’s guidance advises testing water for pH, alkalinity, conductivity, hardness, chloride, and sodium at a minimum. Their lab offers irrigation water tests starting at $35. Their fact sheet shows the ranges found in over 400 water tests submitted, which provides some idea of the variation out there. If your water has high alkalinity, this UMass fact sheet offers management guidance.

11. Use “guardian plants” as part of your IPM program. Guardian plants help protect plants by supporting biological control agents that kill pests. For example, marigolds can be used to manage western flower thrips in combination with predatory mites and a granular form of a commercially available insect-killing fungus to create a self-sustaining IPM system. The UVM Entomology Lab offers this do-it-yourself guide. If you’ve ever had thrips in your tunnels, you know they can be difficult to control.

12. Establish a pest monitoring and scouting program. Using traps and inspecting plants on a regular basis can keep pest problems from becoming unmanageable. Consider assigning one person to be your “IPM scout” performing a weekly walk-through of all tunnels, documenting insect and disease populations, and taking pictures of any symptoms needing identification. UMass Extension has a simple scouting form for common greenhouse insect pests. Yellow sticky cards are handy monitoring tools, but they require getting familiar with what gets stuck on them; see guidance like this from NC State Univ. There are many biological control options for tunnels and greenhouses. These should be preordered in many cases. You can store ladybugs in a fridge if you have a history of aphid problems.

13. Install sensors and alarms. An air temperature alarm and an emergency heater are basic examples of this, but there are many more options for monitors, which should be associated with backup systems or plans in the event of a system failure. Sensors to consider for tunnels are air temperature, soil temperature, relative humidity, irrigation water tank temperature, water pressure, electric voltage, door open/close, carbon monoxide, propane tank level and more. For more info on remote monitoring see the UVM Ag Engineering blog post.

14. Minimize ‘edge effect’ yield losses. I can’t find any article about this but many of you have seen it, too – reduced growth of crops in beds or rows along tunnel edges. It’s probably due to several factors: colder soil (add perimeter insulation), colder air (see HAF fans, above), uneven distribution of nutrients, especially when spreading bulk materials like composts, and maybe just less TLC because it’s often harder to work in the edges of the tunnel. Whatever the reasons, loss of yield along both edges can be significant, so try to avoid the possible causes.

15. Prepare for rodent control (they can move in fast). Options include active measures like traps, rodenticides, cats, etc.) and passive measures like sealing doors, packing up produce, hardware cloth for exclusion, accepting the loss, selling everything early. For more info on these options see a detailed post on the UVM Ag. Engineering blog.

16. Enhance labor efficiency. Take a step back and consider ways to perform tasks more efficiently. Start with tasks that require a lot of time. How long would it take for a flat filler to pay back? How much walking could be avoided when harvesting with the use of carts, or a trolley conveyor? Do you have SOPs to support workers in performing time-consuming tasks efficiently? Check out this overview of ways to lower greenhouse labor costs by, you guessed it, John Bartok. The short section on workstation design for repetitive tasks is worth a read for most growers.