Tag Archives: NYFVI

How do they work? How do I use them? What do biofungicides add to vegetable disease management Part 2

rows of healthy winter squash plants with flags
Winter squash in our cucurbit powdery mildew biopesticide trial conducted in western NY, eastern NY, and on Long Island in 2018. We are also testing biopesticides for white mold. Photo credit: Meg McGrath.

Remember from Part 1 of this post that we (I and many great colleagues) are studying what biopesticides can add to effective disease management of cucurbit powdery mildew and white mold. After “what is a biopesticide?” the next most common questions about this project are about the specific biopesticides we’re testing:

  • How do they work?
  • Can I tank mix them with other pesticides or with fertilizers?
  • Do I need to use these products differently than I would use a chemical pesticide?

Today’s post will try to answer those questions.

 

Modes of action – How do they work?

As you may recall from February’s post, biopesticides work in different ways, and the five biofungicides we’re studying cover the range of these modes of action.

table summarizing modes of action for Contans, Double Nickel, LifeGard, Regalia, and Serifel
Biopesticides protect plants from diseases in different ways. I like to divide them up into the five modes of action (MOAs) in this table. Like many biopesticides, some of the products we are testing have more than one MOA. Click on the table to enlarge it.

Eats pathogen

The fungus active ingredient of Contans (Paraconiothyrium minitans strain CON/M/91-08; formerly called Coniothyrium minitans) “eats” (parasitizes and degrades) the tough sclerotia of the fungus, Sclerotinia sclerotiorum that causes white mold. Sclerotia survive in the soil from year to year. However, for this strategy to be effective, the fungal spores within Contans have to first make contact with the sclerotia. The time between colonization and degradation of sclerotia is about 90 days.

Makes antimicrobial compounds

The active ingredients in Serifel and Double Nickel are bacteria – same species but different strains. They both produce compounds that are harmful to plant pathogens (antimicrobial). According to the manufacturer, most of the foliar efficacy of Double Nickel is due to the antimicrobial compounds already present in the container. But the manufacturer notes that some of the efficacy also comes from the live bacteria that are responsible for this product’s other modes of action, especially the induction of plant resistance (more on this later). The strain of bacteria in Serifel has been formulated so that it contains only living bacteria (no antimicrobial compounds). The manufacturer’s goal is for the bacteria to produce antimicrobial products unique to the specific environmental conditions after application. Double Nickel and Serifel are examples of different strategies for using antimicrobial-producing bacteria to fight plant diseases. Our goal is to explain how the products work; not tell you which strategy is better.

smiling blue bacteria on a leaf; angry yellow bacteria have no place to land
Some biopesticides contain microbes that grow on the plant. These beneficial microbes use up space and nutrients so there is no room for the pathogen, excluding it.

Excludes pathogen

The bacteria in Double Nickel and Serifel also can protect plants from disease by growing over (colonizing) the plant so that there is no space or nutrients available for pathogens. How important this mode of action is to the efficacy of Double Nickel depends on the setting and time of year (according to the manufacturer). Cucurbit leaves exposed to sun, heat, and dry air are not great places for bacteria to grow, and pathogen exclusion is not likely to be very important in protecting cucurbit leaves from powdery mildew. The antimicrobial MOA is more important here. Apple blossoms being protected from fire blight in the early spring could be a different story. The bacteria in Serifel tolerate a wide range of temperatures in the field, but the manufacturer recommends applying this product with a silicon surfactant to help the bacteria spread across the plant surface better.

Induces plant resistance

Plants have mechanisms to defend themselves. Some pathogens succeed in causing disease when they avoid triggering these defenses, or when they infect the plant before it has a chance to activate these defenses. Some biofungicides work by triggering plants to “turn on” their defense mechanisms. This is called “inducing plant resistance.” It is the sole mode of action of the bacteria in LifeGard, and one of the modes of action for the active ingredients in Double Nickel, Regalia, and Serifel.

Promotes plant growth and/or stress tolerance

The last biofungicide being studied in this trial has a plant extract as an active ingredient, instead of a microorganism. Regalia works by both inducing plant resistance, and also promoting plant growth and stress tolerance. Some of the other products in this trial also share these MOAs. According to the label, some crops treated with Regalia produce more chlorophyll or contain more soluble protein. This final MOA (promotion of plant growth and stress tolerance) is also sometimes shared with “biostimulants”. But remember that “biostimulant” is not currently a term regulated by the EPA. This may be changing in the future, so stay tuned. Biostimulants enhance plant health and quality. They are not registered as pesticides, and must not be applied for the purpose of controlling disease. Make sure you read and follow the label of any product you apply.

Best practices – How do I use them?

We’ll get to some product-specific details in a minute, but first some notes about best uses for all five of these products.

  • They need to be used preventatively. For biofungicides to eat pathogens, exclude them from plants, induce plant resistance, or improve plant growth and stress tolerance, they need to beat the pathogen to the plant. It takes time for the plant to fully activate its defenses, even if “flipping the switch” to turn those defenses on happens quickly. The same applies to promoting plant growth and stress tolerance. And if you want the beneficial microorganism to already be growing where the pathogen might land, of course you need to apply the product before the pathogen is present. Microbes that produce antimicrobial compounds also work best if they are applied when disease levels are low.
  • Use IPM. These biofungicides (and most, if not all, biofungicides) were designed to be used with other pest management strategies like good cultural practices, host resistance, and other pesticides. For example, they can be included in a conventional spray program to manage pesticide resistance.
  • Mix what you need, when you need it. Don’t mix biofungicides and then leave them in the spray tank overnight. Some products may need to be used even more promptly. Check the label.
  • Store carefully. Generally, away from direct sunlight and high heat. Follow the storage instructions on the label.
  • They have short intervals, but still require PPE. One of the benefits of biofungicides is short pre-harvest intervals (PHIs) and re-entry intervals (REIs). All five of the products we’re studying have a 0 day PHI and a 4 hour REI. But they all still require personal protective equipment (PPE) when handling and applying them. Read and follow those labels!
  • Tank mixing best practices still apply. The table at the end of this post has details about biological compatibility of these products in tank mixes, as reported by the manufacturers. But just like other pesticides, you need to follow the label instructions for mixing. If you have questions about a specific tank mix partner, confirm compatibility with a company rep. Do a “jar test” if you are mixing two products for the first time and want to know if they are physically compatible.

Biopesticides (especially those that contain living microorganisms) often need to be handled and used differently than chemical pesticides. They may be more sensitive to temperature, moisture, or UV light, which may impact the best time or place to apply them. And of course you don’t want to tank mix a living microorganism with something that will kill the good microbe. (Cleaning your tank well between sprays is always recommended, whether or not you are using a biopesticide.) The following table summarizes details for the five products we’re studying provided by the manufacturers – from product labels, company websites, and conversations with company reps. We have not personally tested this information.

summary of FRAC codes, where and when to apply, temperature tolerance in the field, rainfastness, UV tolerance, tank mix compatibility, storage and shelf life for 5 biopesticides
Exactly how should you use these biofungicides to maximize their efficacy? This table summarizes best practices (as reported by the manufacturers) for each of the five fungicides tested in this trial. Click on the table to enlarge it.

We’ve created handouts that summarize the designs of both the cucurbit powdery mildew and the white mold trials, the modes of action of the five biofungicides we’re testing, and the best practices information presented above.

cucurbit powdery mildew biofungicide trial summary

white mold biofungicide trial summary

Stay tuned for Part 3 of this post – results from our first year of field trials!

 

This post was written by Amara Dunn (NYS IPM) and Sarah Pethybridge (Plant Pathology & Plant-Microbe Biology, School of Integrative Plant Science, Cornell University). Thank you to the New York Farm Viability Institute for funding.

What do biofungicides add to vegetable disease management? Part 1 – Introducing the project

butternut squash plants grown on a black plastic-covered raised bed
This summer we compared three biofungicides added to a conventional cucurbit powdery mildew management program in field trials conducted in western and eastern NY and on Long Island. Photo credit: Caitlin Vore, Cornell Vegetable Program

What we’re doing

This summer I have been working with great colleagues (Elizabeth Buck, Dr. Julie Kikkert, Dr. Margaret McGrath, Jud Reid, and Crystal Stewart) on a project funded by the New York Farm Viability Institute looking at the use of biofungicides (Remember what biofungicides are?) in vegetable disease management. Dr. Darcy Telenko (formerly of the Cornell Vegetable Program) helped plan the project before starting her new position at Purdue University, and Dr. Sarah Pethybridge has provided valuable advice based on her extensive work with white mold (including control with biofungicides). BASF, Bayer, BioWorks, Certis, Dow, and Marrone BioInnovations provided product for the field trials.

The project has two goals:

  1. Quantify what biofungicides add to management of cucurbit powdery mildew and white mold in terms of…
    – disease control
    – yield
    – plant health
    – economic value (comparing yield gains to fungicide costs)
  2. Evaluate the utility of NDVI (normalized difference vegetation index) as a measure of plant health and disease detection in fresh vegetables

Why this project?

For both diseases (cucurbit powdery mildew and white mold), we’re considering biofungicides used with other pest management – other biofungicides, conventional chemical fungicides, and/or cultural practices. Biofungicides are not expected to be silver bullets, and they work best when used in an IPM strategy. But when deciding whether or how to use them in your operation, it’s good to know what value you’re getting for the extra costs of purchasing and applying the products. This summer we ran trials in three major vegetable-producing regions of the state: western New York, eastern NY, and on Long Island.

Biofungicides for cucurbit powdery mildew

cucurbit powdery mildew on the upper side of a squash leaf
Cucurbit powdery mildew looks like a dusting of powdered sugar on the cucurbit leaf. These powdery spots start on the underside of the leaf, and then develop on the upper surface of the leaf, so excellent spray coverage is important. Photo credit: Amara Dunn, NYS IPM

For combatting cucurbit powdery mildew, we’re comparing three biofungicides: LifeGard (Bacillus mycoides isolate J), Regalia (extract from the giant knotweed plant Reynoutria sachalinensis), and Serifel (Bacillus amyloliquefaciens MBI 600). All three were applied weekly starting when the plants were small. Then, when the first signs of powdery mildew showed up, we started a rotation of conventional fungicides (Vivando, Quintec, and Luna Experience). These three treatments plus a rotation of all-organic fungicides (LifeGard, MilStop, Serifel, and a mineral oil) are being compared to two control treatments: the conventional fungicides alone, and plants that received no treatment for powdery mildew. We ran the trials on a variety of bushing acorn squash (‘Honey Bear’) that has intermediate resistance to powdery mildew.

Biofungicides for white mold

bean pod half rotted by white mold fungus
Most vegetable crops are susceptible to white mold, with legumes being among the most vulnerable. The name comes from the dense white “tufts” that the fungus forms. These develop into dark, hard sclerotia that can survive for years in the soil. Photo credit: Amara Dunn, NYS IPM

In the white mold trial, we’re looking at Double Nickel (Bacillus amyloliquefaciens strain D747) alone or in combination with Contans (Paraconiothyrium minitans strain CON/M/91-08; formerly Coniothyrium minitans). Next year we’ll look at these biofungicides in combination with reduced tillage at one site. Reduced tillage is another IPM strategy for white mold. The active ingredient in Contans is a fungus that eats the resting structures (sclerotia) of the fungus that causes the disease white mold. Because of this, it needs time to work, and is applied either in fall or spring. The goal is to reduce the number of sclerotia present in the next crop. Next year we’ll collect data on whether application of Contans reduced disease. In the meantime, during the 2018 growing season treatments we tested were Double Nickel, Cueva (an OMRI-approved copper) and no treatment for white mold on snap bean. Previous research by the EVADE Lab at Cornell AgriTech at The New York State Agricultural Experiment Station, Geneva, New York, has shown that Double Nickel is a promising biofungicide for white mold.

What is NDVI, anyway?

In a nutshell, the “normalized difference vegetation index” (NDVI) is a way to quantify how much healthy, green foliage is present. The device we used emits different types (wavelengths) of light (red and near infrared), and measures how much of each type of light is reflected back from the leaves of the plant. Leaves that are dark green and healthy reflect more infrared light and absorb a lot of red light. Less healthy leaves reflect less infrared light. A NDVI value closer to 1 indicates healthier plants. A NDVI value closer to 0 indicates less healthy plants (or more bare ground).

GreenSeeker device over a dark green (healthy) cucurbit plant and a light green (less healthy) cucurbit plant. Arrows show that red and infrared light are reflected differently from these two plants. NDVI values closer to 1 indicate a lot of healthy green leaves. NDVI values closer to 0 indicate less healthy (or fewer) leaves.
NDVI (normalized difference vegetation index) quantifies the amount of dark green foliage based on how much light of different wavelengths is reflected. It is used in some crops to decide when to apply fertilizer, or to help detect below-ground pests. Photo credit: Amara Dunn, NYS IPM

NDVI and similar indices are already used in other crops and in other places to help growers make decisions about when to fertilize, or to help detect parts of a field where a pest may be present. So far in NY, NDVI is not being widely used by fresh market vegetable growers for disease detection. Collecting NDVI data from this project will do two things:

  1. Help us quantify the health of plants. Even though NDVI is not a measure of disease, we would expect to see more healthy foliage if biofungicides are contributing to disease control.
  2. Provide some preliminary data to help us determine whether NDVI measurements could be useful to NY fresh vegetable growers.
people walking through a winter squash field
Growers and industry reps had a chance to visit the 2018 cucurbit powdery mildew field trials shortly before they were harvested. Photo credit: Amara Dunn, NYS IPM

Field meetings were held at each powdery mildew trial location so that local growers could see the trials and hear about the project. We’re currently wrapping up data analysis from the 2018 field season. You’ll be able to learn about results from the first year of this two-year project at winter meetings around NY, in extension newsletters, and here on this blog. Also, stay tuned for Part 2 of this post with details about how these biofungicides work (modes of action), and how to use them most effectively.

This post was written by Amara Dunn (NYS IPM), Sarah Pethybridge (Plant Pathology & Plant-Microbe Biology, School of Integrative Plant Science, Cornell University), and Darcy Telenko (Department of Botany & Plant Pathology, Purdue University).